Add escape in strings control to ruby parser.

- Moving lines after themselves didnt work.
- moving empty lines deleted them.
- "w" didnt set state to unmodified in generic buffers.
- in "hl" aligned the numbers (by digits)

ARCHITECTURE.md

@@ -0,0 +1,149 @@
+# Base.
+
+### `PCH`
+
+Brings in all the external and standard headers. <br/>
+Apart from c++std stuff we have:
+- `mruby` and almost all it's subheaders.
+- `pcre2` (For regex.)
+- `grapheme.h` - The suckless libgrapheme (to find utf8 boundaries)
+- `unicode_width.h` - To find terminal width of unicode char's.
+
+*Maybe try removing some of them ive probably stopped using.*
+
+### `definitions.h`
+
+- Defines the `bed` namespace
+- Forward declaration of `BEd` type needed by all.
+- `fatal_error` definition, a msg, code (quits application on being thrown)
+- `ed_error`. just a message (stops the current cycle of the ed repl.)
+
+### `bed.h`
+
+**As this is based heavily on the internals, and so ill look into it at the end.**
+
+# `Internal`
+
+## `Vase`
+
+- This module doesn't depend on any other.
+- It's namespace is `bed::internal::vase`
+- Vase is the module to do with the actual storage and handling of a disk backed immutable and reference counted avl piece tree.
+- It is a O(log n) per edit text datatype.
+
+### `constants.h`
+
+Defines `PETAL_SIZE_MAX` as `32 * 1024`.
+- `PETAL_SIZE_MAX` limits teh size of a petal which makes multiple O(n) in petal searches O(1) as it is now bounded.
+
+### `storage/`
+
+A storage is something that stores the actual text, the text is actually stored in storages which are referenced by the trees.
+
+#### `storage.h`
+
+Defines the virtual `Storage` class.
+It has the methods:
+- `const char *read(uint64_t pos)`: reads text from position `pos` and returns a pointer to it.
+- `uint64_t length()`: returns the length of the storage.
+- `void retain() / release()`: Methods to help with refcounted storages.
+
+#### `original.h`
+
+Defines the `Original` type of storage.
+This is a refcounted storage.
+
+It has the fields:
+- `atomic_uint64_t refs{0}`: refcount
+- `const char *buf`: pointer to the actual text.
+- `uint64_t len`
+- `int fd = -1`: the file descriptor of teh undelying disk storage.
+
+It adds the method `initialize` over the base class.
+
+`src/vase/storage/original.cc`.
+
+The constructor uses `mkstemp` to make a temp file, then unlinks it to hide it from the fs but keeps the fd alive.
+
+`initialize` then `mmap`s the fd into a non modifyable pointer managed by the kernel then closes the fd itself.
+- This is what gives us a pointer to the file contents that the kernel can load and evict from memory as needed, and therefore if we have say a 500MB file loaded, but the cursor is arount 200MB and the user is only editing a couple lines around that, the rest of the file will not be using your memory, it might be loaded but if needed the kernel can evict it.
+
+The call site fills the fd before calling initialze, it cannot be modified after that.
+
+#### `append.h`
+
+Defines the `Append` type of storage.
+This is not actually refcounted, it is to be owned by the application just once and reused all throughout.
+It contains the actively typed stuff.
+
+It has the fields:
+- `const char *buf`: pointer to the actual text.
+- `uint64_t allocated_capacity`: the amount of bytees that can be written to it without needing to increase the size.
+- `uint64_t current_size`: Stores the size of actual text stored in it. (the cursor)
+- `int fd = -1`: the file descriptor of the underlying disk storage.
+
+It has the methods `append` (with 2 overloads) and private `grow` over the base class.
+`retain` and `release` do nothing.
+
+`src/vase/storage/append.cc`.
+
+The constructor uses `mkstemp` an `unlink` similar to the original storage.
+It then `ftruncate`s the file to `2^30` bytes or 1GiB this makes writing 1gb to the file possible but does'nt neccasarily use up 1gb on the disk.
+But when `mmap`ing we set `PROT_READ | PROT_WRITE` and `MAP_SHARED` to be able to write edits to disk.
+
+`grow` works by doubling the capacity `ftruncat`ing the fd to the new capacity and then on `linux` it uses `mremap` to remap to the new file size, but otherwise we `munmap` and `mmap` into the new size.
+
+The append methods append text into the buffer (either a single char or char * + len), they may grow the storage size. (the char*+len version uses memcpy).
+
+### `shard.h`
+
+Defines the actual peice tree.
+
+The tree is a polymorhic set of classes.
+
+The base class `Shard` has:
+- `enum Kind : uint8_t kind`: Branch or Petal.
+- `uint16_t height`: the tree height (for avl balancing.)
+- `atomic_uint32_t refs`: the refcount.
+- `uint64_t length`: the length in bytes of this (sub)tree.
+- `uint64_t lines`: the number of `\n` in this subtree.
+- It starts refcount at 1.
+
+The `Branch` class adds:
+- `Shard *left/right` the subtrees.
+- its constructor takes l, r and sets length/lines `(l->length + r->length)`
+- and height `1 + std::max(l->height, r->height)`
+
+The `Petal` (leaf) class adds:
+- `Storage *` a pointer to the storage used.
+- `uint64_t pos` the position in the storage its text starts at.
+- it takes `(uint64_t length, uint64_t lines, Storage *source, uint64_t pos)`
+- it retains `source`. (usefull for refcounted sotrages.)
+
+A `nullptr` `Shard*` is an empty peice of text (i.e. valid).
+
+`src/internal/vase/shard.cc`: defines a set of static function on the Shard class. (All the applications of it.)
+
+the operations methods are:
+- `retain/release` retain/releases them, if freeing a leaf it also releases the storage and for branches it releases both subtrees. nullptr's are ignored.
+- `balance/rotate_(right/left) and height/balance factor` are for doing simple avl balancing operations.
+- `concat` borrows 2 pointers to `Shard` and returns an owned Shard*.
+- `split` borrows a `Shard` and returns a `pair<Shard*, Shard*>` of 2 owned shards.
+- `merge_leaves` works similar to concat but it tries to merge the middle bit if they have their physical representation in order. for example if i have a shard `hell` and i type the letter `o` and because i'd been typing in order the Append storage will have text `hello` we can merge them into a single petal.
+- `append` similar to concat, but uses merge_leaves, useful for small appends like when typing.
+- `build` takes a pointer to an array of `Shard*` and start and end then makes a single avl balanced `Shard*` out of it it is generally faster than calling concat on each peice when we have many.
+
+Then for building a Shard* in the first place we have:
+- `from_command(const char *cmd)` runs the \0 terminated command string and reads its STDOUT and returns an owned Shard*.
+- `from_file(const std::filesystem::path &path)` reads the file at path.
+- `from_string(const char *data, uint64_t len)` loads the string given into a new storage, (normally inserting text can work by inserting into the append storage but this function loads it into a `OriginalStorage` object.).
+These methods all clip the final newline if it exists.
+And they also create a new `OriginalStorage` object.
+
+### `vase.h`
+
+### `iterators/`
+
+#### `line.h`
+
+#### `petal.h`

Makefile

@@ -36,7 +36,7 @@ CFLAGS_RELEASE :=\
 	-fomit-frame-pointer -DNDEBUG -s \
 	-I./include -I./libs/unicode_width
 
-CFLAGS_DEBUG += $(PCRE_CFLAGS) $(LIBGRAPHEME_CFLAGS) $(MRUBY_CFLAGS) $(C_SANITIZER)
+CFLAGS_DEBUG += $(PCRE_CFLAGS) $(LIBGRAPHEME_CFLAGS) $(MRUBY_CFLAGS)
 CFLAGS_RELEASE += $(PCRE_CFLAGS) $(LIBGRAPHEME_CFLAGS) $(MRUBY_CFLAGS)
 
 UNICODE_SRC := $(wildcard libs/unicode_width/*.c)

README.md

@@ -56,5 +56,7 @@ It should support:
 - Error handling.
 - And more.
 
-Not done yet.
+### TODO:
 
+- Make "g" command work.
+- properly handle escapes for %q ' etc in ruby parser (rn everything is escapable.)

flake.nix

@@ -70,9 +70,8 @@
 
         buildPhase = ''
           make \
-            MRBC=${mruby}/bin/mrbc \
+            MRUBY_CFLAGS="-I${mruby}/include" \
-            MRUBY_CFLAGS=-I${mruby}/include \
+            MRUBY_LIBS="-L${mruby}/lib -lmruby"
-            MRUBY_LIBS=-L${mruby}/lib -lmruby
         '';
 
         installPhase = ''
@@ -110,10 +109,8 @@
           export CC="ccache $CC"
           export CXX="ccache $CXX"
 
-          export MRBC=${mruby}/bin/mrbc
           export MRUBY_CFLAGS=-I${mruby}/include
           export MRUBY_LIBS="-L${mruby}/lib -lmruby"
-          export PATH="$PWD/result/bin:$PATH"
         '';
       };
     };

include/bed.h

@@ -6,6 +6,7 @@
 #include "internal/functions/suffixes.h"
 #include "internal/io/io.h"
 #include "internal/marks/marks.h"
+#include "internal/scripting/ruby.h"
 #include "internal/theme/theme.h"
 #include "internal/ui/command.h"
 #include "internal/ui/text_mode.h"
@@ -13,6 +14,7 @@
 
 namespace bed {
 struct BEd {
+  internal::scripting::RubyState mrb;
   internal::trie::Trie<internal::functions::Function> functions;
   internal::functions::Function no_op;
   internal::functions::Function eof_op;
@@ -21,6 +23,7 @@ struct BEd {
   std::unordered_map<std::string, internal::syntax::Language *> languages;
   internal::io::IO io;
   internal::vase::AppendStorage append{"/tmp"};
+  std::unordered_map<std::string, internal::buffer::Buffer *> buffers;
 
   bool help_mode = false;
   bool prompt_mode = true;
@@ -34,8 +37,6 @@ struct BEd {
   std::string last_replacement = "";
   std::string last_shell = "";
 
-  std::unordered_map<std::string, internal::buffer::Buffer *> buffers;
-
   internal::buffer::Range prev_1;
   internal::buffer::Range prev_2;
   internal::marks::MarksEngine marks;

include/internal/buffer/decl.h

@@ -34,6 +34,7 @@ struct Buffer {
   virtual uint64_t bytes() = 0;
   virtual void set_filename(std::filesystem::path path) = 0;
   virtual std::filesystem::path filename() = 0;
+  virtual void saved_hook() = 0;
   virtual void load(BEd &ctx, vase::Shard *text) = 0;
   virtual vase::Shard *copy(uint64_t start_line, uint64_t end_line) = 0;
   virtual void substitute(

include/internal/buffer/types/clip.h

@@ -10,6 +10,7 @@ struct ClipBuffer : Buffer {
 
   void clip_write(vase::Shard *text);
   bool waste() override;
+  void saved_hook() override;
   uint64_t lines() override;
   uint64_t bytes() override;
   void load(BEd &ctx, vase::Shard *text) override;

include/internal/buffer/types/generic.h

@@ -14,8 +14,8 @@ struct HistoryItem {
 
 struct GenericBuffer : ShardBuffer {
   uint64_t base_version{0};
-  std::chrono::system_clock::time_point timestamp;
+  std::chrono::system_clock::time_point timestamp{std::chrono::system_clock::now()};
-  std::string action;
+  std::string action{"Created buffer."};
   std::filesystem::path save_path{};
   std::vector<HistoryItem> undo_stack;
   std::vector<HistoryItem> redo_stack;
@@ -24,12 +24,14 @@ struct GenericBuffer : ShardBuffer {
       : ShardBuffer(name, nullptr, nullptr, Kind::Generic) {}
   ~GenericBuffer();
 
+  void language(BEd &ctx, std::string name);
   void list_history(BEd &ctx);
   ReadonlyBuffer *get_history(uint64_t version);
   void snapshot(std::string action);
   bool undo(BEd &ctx);
   bool redo(BEd &ctx);
   uint64_t prune(int);
+  void saved_hook() override;
   bool waste() override;
   void load(BEd &ctx, vase::Shard *text) override;
   void set_filename(std::filesystem::path path) override;

include/internal/buffer/types/readonly.h

@@ -12,6 +12,7 @@ struct ReadonlyBuffer : ShardBuffer {
     const syntax::ParserSnapshot &snapshot
   ) : ShardBuffer(std::move(name), root, snapshot, Kind::History) {}
 
+  void saved_hook() override {}
   bool waste() override {
     return useless;
   }

include/internal/scripting/ruby.h

@@ -0,0 +1,124 @@
+#pragma once
+
+#include "definitions.h"
+#include "pch.h"
+
+namespace bed::internal::scripting {
+struct RubyState {
+  mrb_state *state = nullptr;
+  int arena = 0;
+
+  explicit RubyState(BEd *ctx) : state(mrb_open()) {
+    if (!state)
+      throw fatal_error("Failed to initialize mruby.", 1);
+    state->ud = ctx;
+    arena = mrb_gc_arena_save(state);
+  }
+
+  ~RubyState() {
+    state->ud = nullptr;
+    if (state) {
+      mrb_gc_arena_restore(state, arena);
+      mrb_full_gc(state);
+      mrb_close(state);
+    }
+  }
+
+  RubyState(const RubyState &) = delete;
+  RubyState &operator=(const RubyState &) = delete;
+};
+
+struct Block {
+  mrb_state *mrb = nullptr;
+  mrb_value proc = mrb_nil_value();
+
+  Block(mrb_state *mrb, mrb_value proc) noexcept
+      : mrb(mrb), proc(proc) {
+    mrb_gc_register(mrb, proc);
+  }
+
+  Block() noexcept = default;
+
+  ~Block() noexcept {
+    if (!mrb_nil_p(proc) && mrb)
+      mrb_gc_unregister(mrb, proc);
+  }
+
+  Block(const Block &other) noexcept
+      : mrb(other.mrb), proc(other.proc) {
+    if (mrb && !mrb_nil_p(proc))
+      mrb_gc_register(mrb, proc);
+  }
+
+  Block &operator=(const Block &other) noexcept {
+    if (this != &other) {
+      if (mrb && !mrb_nil_p(proc))
+        mrb_gc_unregister(mrb, proc);
+      mrb = other.mrb;
+      proc = other.proc;
+      if (mrb && !mrb_nil_p(proc))
+        mrb_gc_register(mrb, proc);
+    }
+    return *this;
+  }
+
+  Block(Block &&other) noexcept
+      : mrb(other.mrb), proc(other.proc) {
+    other.mrb = nullptr;
+    other.proc = mrb_nil_value();
+  }
+
+  Block &operator=(Block &&other) noexcept {
+    if (this != &other) {
+      if (mrb && !mrb_nil_p(proc))
+        mrb_gc_unregister(mrb, proc);
+      mrb = other.mrb;
+      proc = other.proc;
+      other.mrb = nullptr;
+      other.proc = mrb_nil_value();
+    }
+    return *this;
+  }
+
+  void set_proc(mrb_state *mrb_, mrb_value new_proc) {
+    if (!mrb_nil_p(proc) && mrb)
+      mrb_gc_unregister(mrb, proc);
+    mrb = mrb_;
+    proc = new_proc;
+    mrb_gc_register(mrb, proc);
+  }
+
+  mrb_value call(int argc = 0, mrb_value *argv = nullptr) const {
+    if (mrb_nil_p(proc))
+      return mrb_nil_value();
+    mrb_value result = mrb_funcall_argv(mrb, proc, mrb_intern_cstr(mrb, "call"), argc, argv);
+    if (!mrb->exc)
+      return result;
+    mrb_value exc = mrb_obj_value(mrb->exc);
+    mrb_value msg = mrb_funcall(mrb, exc, "message", 0);
+    std::string error;
+    if (mrb_string_p(msg))
+      error.assign(RSTRING_PTR(msg), RSTRING_LEN(msg));
+    auto *fatal_class = mrb_class_get(mrb, "FatalError");
+    if (mrb_obj_is_kind_of(mrb, exc, fatal_class)) {
+      mrb_value code =
+        mrb_iv_get(mrb, exc, mrb_intern_lit(mrb, "@code"));
+      mrb->exc = nullptr;
+      int c = 1;
+      if (mrb_fixnum_p(code))
+        c = mrb_fixnum(code);
+      throw fatal_error(error, c);
+    }
+    auto *ed_class = mrb_class_get(mrb, "EdError");
+    if (mrb_obj_is_kind_of(mrb, exc, ed_class)) {
+      mrb->exc = nullptr;
+      throw ed_error(error);
+    }
+    mrb->exc = nullptr;
+    throw ed_error("Ruby Exception: " + error);
+  }
+};
+
+void register_basic(BEd &ctx);
+std::string run(BEd &ctx, const std::string &str);
+}; // namespace bed::internal::scripting

include/internal/syntax/decl.h

@@ -48,6 +48,7 @@ struct ParseState {
     uint64_t line, uint64_t original, uint64_t final
   );
   static ParseState *concat(Language &lang, ParseState *a, ParseState *b);
+  static void *state_before(Language &lang, ParseState *root, vase::Shard *vase, uint64_t line);
 };
 
 struct ParseStateBranch : ParseState {
@@ -83,18 +84,25 @@ struct ParsePieceBuilder {
   std::vector<ParseState *> pieces;
   std::vector<uint16_t> blocks;
   void *piece_state{nullptr};
+  void *prev_state{nullptr};
   uint64_t chunk_start{0};
   uint64_t chunk_lines{0};
-  ParsePieceBuilder(Language &lang, uint64_t first_line)
+  ParsePieceBuilder(Language &lang, uint64_t first_line, void *entry_state)
-      : lang(lang), chunk_start(first_line) {}
+      : lang(lang), chunk_start(first_line) {
-  void add(
+    prev_state = lang.copy(entry_state);
-    void *state,
+  }
-    uint64_t line,
+  ~ParsePieceBuilder() {
-    const std::vector<ParseEvent> &events
+    if (prev_state)
-  ) {
+      lang.destroy(prev_state);
+    if (piece_state)
+      lang.destroy(piece_state);
+  }
+  ParsePieceBuilder(const ParsePieceBuilder &) = delete;
+  ParsePieceBuilder &operator=(const ParsePieceBuilder &) = delete;
+  void add(void *state, uint64_t line, const std::vector<ParseEvent> &events) {
     if (chunk_lines == 0) {
       chunk_start = line;
-      piece_state = lang.copy(state);
+      piece_state = lang.copy(prev_state);
     }
     for (const auto &ev : events) {
       blocks.push_back(
@@ -103,6 +111,9 @@ struct ParsePieceBuilder {
       );
     }
     ++chunk_lines;
+    if (prev_state)
+      lang.destroy(prev_state);
+    prev_state = lang.copy(state);
     if (chunk_lines == ParseStateLeaf::MAX_CHUNK)
       flush();
   }

include/internal/syntax/parser.h

@@ -13,6 +13,7 @@ ParserSnapshot make_parser(vase::Shard *vase, uint64_t lines, Language *lang);
 ParserSnapshot retain(const ParserSnapshot &snap);
 void release(ParserSnapshot &snap);
 
+void *state_before(const ParserSnapshot &snap, vase::Shard *vase, uint64_t line);
 uint64_t next_closing(const ParserSnapshot &snap, uint64_t line);
 uint64_t prev_opening(const ParserSnapshot &snap, uint64_t line);
 

include/internal/syntax/ruby/decl.h

@@ -24,7 +24,8 @@ struct alignas(2) RubyState {
       DEF_NAME = 0b10,
       MODULE_NAME = 0b11
     };
-    static constexpr uint8_t NEWLINE = 1 << 5;
+    static constexpr uint8_t NEWLINE = 1 << 4;
+    static constexpr uint8_t ALLOW_ESCAPE = 1 << 5;
     static constexpr uint8_t ALLOW_INTERPOLATION = 1 << 6;
     static constexpr uint8_t EXPECTING_EXPRESSION = 1 << 7;
     uint8_t flags = 0;

include/internal/syntax/ruby/tries.h

@@ -68,6 +68,11 @@ const static std::vector<std::string> builtins = {
 };
 
 const static std::vector<std::string> methods = {
+  // BEd methods.
+  "handle",
+  "register",
+  "unregister",
+  // Normal:
   "abort",
   "at_exit",
   "binding",

include/internal/vase/shard.h

@@ -24,9 +24,9 @@ struct Shard {
   static void retain(Shard *n);
   static void release(Shard *n);
 
-  static Shard *from_file(const std::filesystem::path &path, bool posix_ending);
+  static Shard *from_file(const std::filesystem::path &path);
-  static Shard *from_string(const char *data, uint64_t len, bool posix_ending);
+  static Shard *from_string(const char *data, uint64_t len);
-  static Shard *from_command(const char *cmd, bool posix_ending);
+  static Shard *from_command(const char *cmd);
 
   static std::pair<Shard *, Shard *> split(Shard *n, uint64_t offset);
   static Shard *concat(Shard *a, Shard *b);

include/pch.h

@@ -4,10 +4,29 @@
 
 #include <mruby.h>
 #include <mruby/array.h>
+#include <mruby/boxing_word.h>
+#include <mruby/class.h>
+#include <mruby/common.h>
 #include <mruby/compile.h>
+#include <mruby/data.h>
+#include <mruby/dump.h>
+#include <mruby/error.h>
+#include <mruby/gc.h>
 #include <mruby/hash.h>
+#include <mruby/internal.h>
 #include <mruby/irep.h>
+#include <mruby/numeric.h>
+#include <mruby/object.h>
+#include <mruby/opcode.h>
+#include <mruby/presym.h>
+#include <mruby/proc.h>
+#include <mruby/range.h>
+#include <mruby/re.h>
 #include <mruby/string.h>
+#include <mruby/throw.h>
+#include <mruby/value.h>
+#include <mruby/variable.h>
+#include <mruby/version.h>
 #include <pcre2.h>
 extern "C" {
 #include <grapheme.h>

samples/bed.rb

@@ -0,0 +1,3 @@
+register :happy, address: :none do
+  puts "be nice"
+end

src/bed/bed.cc

@@ -0,0 +1,73 @@
+#include "bed.h"
+
+namespace bed {
+BEd::BEd(std::vector<std::string> args)
+    : mrb(this), theme(internal::theme::Theme::default_theme()), io(*this) {
+  std::string prompt_ = "";
+  std::string file = "";
+  bool suppress = false;
+  bool color = true;
+  for (size_t i = 1; i < args.size(); i++) {
+    if (args[i] == "-p") {
+      i++;
+      if (i >= args.size())
+        throw fatal_error("Prompt not specified!", 1);
+      prompt_ = args[i];
+    } else if (args[i] == "-s") {
+      suppress = true;
+    } else if (args[i] == "--no-color") {
+      color = false;
+    } else if (args[i] == "-v" || args[i] == "--verbose") {
+      help_mode = true;
+    } else if (args[i] == "-h" || args[i] == "--help") {
+      print_help();
+      throw fatal_error("", 0);
+    } else {
+      if (file.size())
+        throw fatal_error("Invalid arguments given.", 1);
+      file = args[i];
+    }
+  }
+  if (prompt_ != "")
+    prompt = [p = std::move(prompt_)](BEd &) { return p; };
+  else
+    prompt_mode = false;
+  suppress_mode = suppress;
+  const char *no_color = getenv("NO_COLOR");
+  if (no_color && *no_color != '\0')
+    color = false;
+  const char *colorterm = getenv("COLORTERM");
+  if (colorterm
+      && strcmp(colorterm, "truecolor") != 0
+      && strcmp(colorterm, "24bit") != 0)
+    color = false;
+  color_mode = color;
+  internal::functions::Function::register_posix(*this);
+  internal::functions::Function::register_extented(*this);
+  internal::functions::Suffix::register_suffixes(*this);
+  internal::scripting::register_basic(*this);
+  languages["ruby"] = new internal::syntax::Language(internal::syntax::ruby::lang_ruby());
+  buffers["clip"] = new internal::buffer::ClipBuffer("clip");
+  current() = {"default", 0};
+  try {
+    if (file != "")
+      handle(":default:E " + file, false);
+  } catch (ed_error &e) {
+    io.write_line("?");
+    if (help_mode)
+      io.write_line(e.what());
+    last_help = e.what();
+  }
+}
+
+BEd::~BEd() {
+  for (auto &[_, buffer] : buffers)
+    delete buffer;
+  for (auto &[_, lang] : languages)
+    delete lang;
+}
+
+void BEd::print_help() {
+  io.write("BEd - A line editor.\n");
+}
+} // namespace bed

src/bed/handle.cc

@@ -0,0 +1,115 @@
+#include "bed.h"
+#include "internal/parser/parser.h"
+
+namespace bed {
+void BEd::handle(std::string_view cmd, bool eof) {
+  if (eof && cmd.empty()) {
+    eof_op.handle(*this, "", nullptr, std::monostate(), nullptr);
+    return;
+  }
+  internal::parser::Command c = internal::parser::Parser::get_command(cmd, *this);
+  if (c.temp_address) {
+    marks.get(251) = marks.get(250);
+    prev_2 = prev_1;
+    temporary_current = true;
+  }
+  internal::buffer::Address address;
+  switch (c.function->address_kind) {
+  case internal::functions::Function::AddressKind::None: {
+    auto a = internal::parser::AddressPromise::get_line(*this, c.addresses);
+    if (!a.has_value()) {
+      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
+      a = internal::parser::AddressPromise::get_line(*this, vec);
+      if (!a.has_value())
+        a = current();
+    }
+    address = a->buffername;
+  } break;
+  case internal::functions::Function::AddressKind::Line: {
+    auto a = internal::parser::AddressPromise::get_line(*this, c.addresses);
+    if (!a.has_value()) {
+      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
+      a = internal::parser::AddressPromise::get_line(*this, vec);
+      if (!a.has_value())
+        a = current();
+    }
+    address = *a;
+  } break;
+  case internal::functions::Function::AddressKind::Range: {
+    auto a = internal::parser::AddressPromise::get_range(*this, c.addresses);
+    if (!a.has_value()) {
+      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
+      a = internal::parser::AddressPromise::get_range(*this, vec);
+      if (!a.has_value())
+        a = internal::buffer::Range(current(), current());
+    }
+    address = *a;
+  } break;
+  }
+  if (std::holds_alternative<internal::buffer::Line>(c.argument)) {
+    if (c.argument_addresses.empty())
+      throw ed_error("Function needs address argument.");
+    auto a = internal::parser::AddressPromise::get_line(*this, c.argument_addresses);
+    if (a.has_value())
+      c.argument = *a;
+    else
+      c.argument = current();
+  } else if (std::holds_alternative<internal::buffer::Range>(c.argument)) {
+    if (c.argument_addresses.empty())
+      throw ed_error("Function needs address argument.");
+    auto a = internal::parser::AddressPromise::get_range(*this, c.argument_addresses);
+    if (a.has_value())
+      c.argument = *a;
+    else
+      c.argument = internal::buffer::Range(current(), current());
+  }
+  if (!c.function->accept_zero) {
+    if (std::holds_alternative<internal::buffer::Line>(address)) {
+      if (std::get<internal::buffer::Line>(address).number == 0)
+        throw ed_error("Line number can't be zero.");
+    } else if (std::holds_alternative<internal::buffer::Range>(address)) {
+      auto r = std::get<internal::buffer::Range>(address);
+      if (r.start == 0 || r.end == 0)
+        throw ed_error("Line number can't be zero.");
+    }
+  }
+  internal::vase::Shard *text = nullptr;
+  if (c.function->input_mode == internal::functions::Function::InputMode::Text) {
+    internal::vase::Shard *vase = nullptr;
+    internal::syntax::Language *lang = nullptr;
+    void *state = nullptr;
+    if (c.function->pre_text_mode)
+      std::tie(vase, lang, state) = c.function->pre_text_mode(*this, address, c.argument);
+    internal::ui::text_mode::TextMode tm(*this, vase, lang, state);
+    auto [a, b] = tm.run();
+    if (!b) {
+      text = a;
+    } else {
+      if (a) {
+        auto p = internal::syntax::make_parser(a, a->lines + 1, lang);
+        auto cancel_buf = new internal::buffer::ReadonlyBuffer("cancel", a, p);
+        internal::syntax::release(p);
+        buffers["cancel"] = cancel_buf;
+        cancel_buf->useless = false;
+        internal::vase::Shard::release(a);
+      }
+      throw ed_error("Operation cancelled.");
+    }
+  }
+  if (c.function->handle)
+    c.function->handle(*this, address, text, c.argument, nullptr);
+  if (c.suffix)
+    c.suffix->handle(*this);
+  if (c.temp_address)
+    temporary_current = false;
+  for (auto it = buffers.begin(); it != buffers.end();) {
+    internal::buffer::Buffer *buf = it->second;
+    if (buf->waste()) {
+      delete buf;
+      it = buffers.erase(it);
+    } else {
+      ++it;
+    }
+  }
+}
+} // namespace bed

src/bed/run.cc

@@ -2,82 +2,13 @@
 #include "internal/parser/parser.h"
 
 namespace bed {
-BEd::BEd(std::vector<std::string> args)
-    : theme(internal::theme::Theme::default_theme()), io(*this) {
-  std::string prompt_ = "";
-  std::string file = "";
-  bool suppress = false;
-  bool color = true;
-  for (size_t i = 1; i < args.size(); i++) {
-    if (args[i] == "-p") {
-      i++;
-      if (i >= args.size())
-        throw fatal_error("Prompt not specified!", 1);
-      prompt_ = args[i];
-    } else if (args[i] == "-s") {
-      suppress = true;
-    } else if (args[i] == "--no-color") {
-      color = false;
-    } else if (args[i] == "-v" || args[i] == "--verbose") {
-      help_mode = true;
-    } else if (args[i] == "-h" || args[i] == "--help") {
-      print_help();
-      throw fatal_error("", 0);
-    } else {
-      if (file.size())
-        throw fatal_error("Invalid arguments given.", 1);
-      file = args[i];
-    }
-  }
-  if (prompt_ != "")
-    prompt = [p = std::move(prompt_)](BEd &) { return p; };
-  else
-    prompt_mode = false;
-  suppress_mode = suppress;
-  const char *no_color = getenv("NO_COLOR");
-  if (no_color && *no_color != '\0')
-    color = false;
-  const char *colorterm = getenv("COLORTERM");
-  if (colorterm
-      && strcmp(colorterm, "truecolor") != 0
-      && strcmp(colorterm, "24bit") != 0)
-    color = false;
-  color_mode = color;
-  internal::functions::Function::register_posix(*this);
-  internal::functions::Function::register_extented(*this);
-  internal::functions::Suffix::register_suffixes(*this);
-  languages["ruby"] = new internal::syntax::Language(internal::syntax::ruby::lang_ruby());
-  buffers["clip"] = new internal::buffer::ClipBuffer("clip");
-  current() = {"default", 0};
-  try {
-    if (file != "")
-      handle(":default:E " + file, false);
-  } catch (ed_error &e) {
-    io.write_line("?");
-    if (help_mode)
-      io.write_line(e.what());
-    last_help = e.what();
-  }
-}
-
-BEd::~BEd() {
-  for (auto &[_, buffer] : buffers)
-    delete buffer;
-  for (auto &[_, lang] : languages)
-    delete lang;
-}
-
-void BEd::print_help() {
-  io.write("BEd - A line editor.\n");
-}
-
 void BEd::run() {
   while (true) {
     internal::ui::CommandIO command(*this);
     auto [cmd, eof] = command.run();
     try {
       handle(cmd, eof);
-    } catch (ed_error &e) {
+    } catch (const ed_error &e) {
       io.apply(internal::io::Token::Warning);
       io.write_line("?");
       if (help_mode)
@@ -88,117 +19,6 @@ void BEd::run() {
   }
 }
 
-void BEd::handle(std::string_view cmd, bool eof) {
-  if (eof && cmd.empty()) {
-    eof_op.handle(*this, "", nullptr, std::monostate(), nullptr);
-    return;
-  }
-  internal::parser::Command c = internal::parser::Parser::get_command(cmd, *this);
-  if (c.temp_address) {
-    marks.get(251) = marks.get(250);
-    prev_2 = prev_1;
-    temporary_current = true;
-  }
-  internal::buffer::Address address;
-  switch (c.function->address_kind) {
-  case internal::functions::Function::AddressKind::None: {
-    auto a = internal::parser::AddressPromise::get_line(*this, c.addresses);
-    if (!a.has_value()) {
-      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
-      a = internal::parser::AddressPromise::get_line(*this, vec);
-      if (!a.has_value())
-        a = current();
-    }
-    address = a->buffername;
-  } break;
-  case internal::functions::Function::AddressKind::Line: {
-    auto a = internal::parser::AddressPromise::get_line(*this, c.addresses);
-    if (!a.has_value()) {
-      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
-      a = internal::parser::AddressPromise::get_line(*this, vec);
-      if (!a.has_value())
-        a = current();
-    }
-    address = *a;
-  } break;
-  case internal::functions::Function::AddressKind::Range: {
-    auto a = internal::parser::AddressPromise::get_range(*this, c.addresses);
-    if (!a.has_value()) {
-      auto vec = internal::parser::Parser::get_addresses(c.function->default_address, *this);
-      a = internal::parser::AddressPromise::get_range(*this, vec);
-      if (!a.has_value())
-        a = internal::buffer::Range(current(), current());
-    }
-    address = *a;
-  } break;
-  }
-  if (std::holds_alternative<internal::buffer::Line>(c.argument)) {
-    if (c.argument_addresses.empty())
-      throw ed_error("Function needs address argument.");
-    auto a = internal::parser::AddressPromise::get_line(*this, c.argument_addresses);
-    if (a.has_value())
-      c.argument = *a;
-    else
-      c.argument = current();
-  } else if (std::holds_alternative<internal::buffer::Range>(c.argument)) {
-    if (c.argument_addresses.empty())
-      throw ed_error("Function needs address argument.");
-    auto a = internal::parser::AddressPromise::get_range(*this, c.argument_addresses);
-    if (a.has_value())
-      c.argument = *a;
-    else
-      c.argument = internal::buffer::Range(current(), current());
-  }
-  if (!c.function->accept_zero) {
-    if (std::holds_alternative<internal::buffer::Line>(address)) {
-      if (std::get<internal::buffer::Line>(address).number == 0)
-        throw ed_error("Line number can't be zero.");
-    } else if (std::holds_alternative<internal::buffer::Range>(address)) {
-      auto r = std::get<internal::buffer::Range>(address);
-      if (r.start == 0 || r.end == 0)
-        throw ed_error("Line number can't be zero.");
-    }
-  }
-  internal::vase::Shard *text = nullptr;
-  if (c.function->input_mode == internal::functions::Function::InputMode::Text) {
-    internal::vase::Shard *vase = nullptr;
-    internal::syntax::Language *lang = nullptr;
-    void *state = nullptr;
-    if (c.function->pre_text_mode)
-      std::tie(vase, lang, state) = c.function->pre_text_mode(*this, address, c.argument);
-    internal::ui::text_mode::TextMode tm(*this, vase, lang, state);
-    auto [a, b] = tm.run();
-    if (!b) {
-      text = a;
-    } else {
-      if (a) {
-        auto p = internal::syntax::make_parser(a, a->lines + 1, lang);
-        auto cancel_buf = new internal::buffer::ReadonlyBuffer("cancel", a, p);
-        internal::syntax::release(p);
-        buffers["cancel"] = cancel_buf;
-        cancel_buf->useless = false;
-        internal::vase::Shard::release(a);
-      }
-      throw ed_error("Operation cancelled.");
-    }
-  }
-  if (c.function->handle)
-    c.function->handle(*this, address, text, c.argument, nullptr);
-  if (c.suffix)
-    c.suffix->handle(*this);
-  if (c.temp_address)
-    temporary_current = false;
-  for (auto it = buffers.begin(); it != buffers.end();) {
-    internal::buffer::Buffer *buf = it->second;
-    if (buf->waste()) {
-      delete buf;
-      it = buffers.erase(it);
-    } else {
-      ++it;
-    }
-  }
-}
-
 internal::buffer::Buffer &BEd::buffer(const std::string &name) {
   if (name.empty())
     throw ed_error("Can't have empty buffer name");

src/internal/buffer/generic.cc

@@ -15,6 +15,8 @@ GenericBuffer::~GenericBuffer() {
 
 void GenericBuffer::list_history(BEd &ctx) {
   uint64_t current = base_version + undo_stack.size();
+  uint64_t max_version = current + redo_stack.size();
+  size_t width = std::to_string(max_version).size();
   for (size_t i = 0; i < undo_stack.size(); ++i) {
     auto &item = undo_stack[i];
     uint64_t version = base_version + i;
@@ -22,8 +24,9 @@ void GenericBuffer::list_history(BEd &ctx) {
     std::tm tm = *std::localtime(&time);
     ctx.io.write_line(
       std::format(
-        "  {}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
+        "  {:>{}}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
         version,
+        width,
         tm.tm_year + 1900,
         tm.tm_mon + 1,
         tm.tm_mday,
@@ -39,8 +42,9 @@ void GenericBuffer::list_history(BEd &ctx) {
     std::tm tm = *std::localtime(&time);
     ctx.io.write_line(
       std::format(
-        "* {}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
+        "* {:>{}}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
         current,
+        width,
         tm.tm_year + 1900,
         tm.tm_mon + 1,
         tm.tm_mday,
@@ -58,8 +62,9 @@ void GenericBuffer::list_history(BEd &ctx) {
     std::tm tm = *std::localtime(&time);
     ctx.io.write_line(
       std::format(
-        "  {}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
+        "  {:>{}}  {:04}-{:02}-{:02} {:02}:{:02}:{:02} {}",
         version,
+        width,
         tm.tm_year + 1900,
         tm.tm_mon + 1,
         tm.tm_mday,
@@ -203,7 +208,27 @@ uint64_t GenericBuffer::prune(int keep) {
 bool GenericBuffer::waste() {
   return save_path.empty()
          && root == nullptr
-         && undo_stack.empty();
+         && undo_stack.empty()
+         && parse.lang == nullptr;
+}
+
+void GenericBuffer::saved_hook() {
+  state = buffer::GenericBuffer::Unmodified;
+}
+
+void GenericBuffer::language(BEd &ctx, std::string name) {
+  syntax::Language *lang = nullptr;
+  if (name.size()) {
+    auto it = ctx.languages.find(name);
+    if (it == ctx.languages.end())
+      throw ed_error("Language not found.");
+    lang = it->second;
+  }
+  if (lang == parse.lang)
+    return;
+  snapshot("Change buffer language.");
+  syntax::release(parse);
+  parse = syntax::make_parser(root, lines(), lang);
 }
 
 void GenericBuffer::load(BEd &ctx, vase::Shard *text) {
@@ -225,7 +250,7 @@ void GenericBuffer::load(BEd &ctx, vase::Shard *text) {
   }
   ctx.current() = {name, lines()};
   syntax::release(parse);
-  parse = syntax::make_parser(root, lines(), ctx.languages["ruby"]);
+  parse = syntax::make_parser(root, lines(), nullptr);
 }
 
 void GenericBuffer::set_filename(std::filesystem::path path) {
@@ -237,17 +262,15 @@ std::filesystem::path GenericBuffer::filename() {
 };
 
 void GenericBuffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
-  if (!text)
+  snapshot(std::format("Insert {} lines after line {}", (text ? text->lines + 1 : 1), line));
-    return;
-  snapshot(std::format("Insert {} lines after line {}", text->lines + 1, line));
   ctx.prev().buffername = name;
   ctx.prev().start = line + 1;
-  ctx.prev().end = line + text->lines + 1;
+  ctx.prev().end = line + (text ? text->lines + 1 : 1);
-  ctx.current() = {name, line + text->lines + 1};
+  ctx.current() = {name, line + (text ? text->lines + 1 : 1)};
   root = vase::insert(&ctx.append, root, text, line);
-  ctx.marks.insert(name, line, text->lines + 1);
+  ctx.marks.insert(name, line, (text ? text->lines + 1 : 1));
   if (parse.lang)
-    syntax::insert(parse, root, line, text->lines + 1);
+    syntax::insert(parse, root, line, (text ? text->lines + 1 : 1));
   state = Modified;
 }
 

src/internal/buffer/special/clip.cc

@@ -8,15 +8,17 @@ bool ClipBuffer::waste() {
   return false;
 }
 
+void ClipBuffer::saved_hook() {}
+
 uint64_t ClipBuffer::lines() {
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   uint64_t lines = s ? s->lines + 1 : 0;
   vase::Shard::release(s);
   return lines;
 }
 
 uint64_t ClipBuffer::bytes() {
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   uint64_t length = s ? s->length + 1 : 0;
   vase::Shard::release(s);
   return length;
@@ -55,7 +57,7 @@ void ClipBuffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
   ctx.prev().buffername = name;
   ctx.prev().start = line + 1;
   ctx.prev().end = line + (text ? text->lines + 1 : 0);
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   s = vase::insert(&ctx.append, s, text, line);
   clip_write(s);
   vase::Shard::release(s);
@@ -63,7 +65,7 @@ void ClipBuffer::append(BEd &ctx, vase::Shard *text, uint64_t line) {
 }
 
 void ClipBuffer::remove(BEd &ctx, uint64_t start_line, uint64_t end_line) {
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   s = vase::erase(s, start_line, end_line);
   clip_write(s);
   ctx.prev().buffername = name;
@@ -83,7 +85,7 @@ void ClipBuffer::replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint6
   ctx.prev().end = start_line + text->lines;
   uint64_t new_count = text->lines + 1;
   uint64_t old_count = end_line - start_line + 1;
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   s = vase::replace(s, text, start_line, end_line);
   clip_write(s);
   vase::Shard::release(s);
@@ -97,7 +99,7 @@ void ClipBuffer::replace(BEd &ctx, vase::Shard *text, uint64_t start_line, uint6
 }
 
 void ClipBuffer::join(BEd &ctx, uint64_t start_line, uint64_t end_line) {
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   s = vase::join(s, start_line, end_line);
   clip_write(s);
   vase::Shard::release(s);
@@ -114,7 +116,7 @@ void ClipBuffer::substitute(
   ctx.prev().buffername = name;
   ctx.prev().start = start_line;
   ctx.prev().end = end_line;
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   s = vase::substitute(
     &ctx.append,
     s,
@@ -136,21 +138,21 @@ void ClipBuffer::substitute(
 }
 
 vase::Shard *ClipBuffer::copy(uint64_t start_line, uint64_t end_line) {
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   vase::Shard *o = vase::copy(s, start_line, end_line);
   vase::Shard::release(s);
   return o;
 }
 
 uint64_t ClipBuffer::find_next(std::string_view pattern, uint64_t start) {
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   uint64_t line = vase::find_next(s, pattern, start);
   vase::Shard::release(s);
   return line;
 }
 
 uint64_t ClipBuffer::find_prev(std::string_view pattern, uint64_t start) {
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   uint64_t line = vase::find_prev(s, pattern, start);
   vase::Shard::release(s);
   return line;
@@ -174,7 +176,7 @@ void ClipBuffer::print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
   ctx.prev().buffername = name;
   ctx.prev().start = start_line;
   ctx.prev().end = end_line;
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   vase::Iterator it(s, start_line - 1, Direction::Forward);
   while (it.next() && start_line++ <= end_line)
     ctx.io.write_line(it.line);
@@ -188,7 +190,7 @@ void ClipBuffer::number_print(BEd &ctx, uint64_t start_line, uint64_t end_line)
   uint8_t width = 1;
   for (uint64_t n = end_line; n >= 10; n /= 10)
     ++width;
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   vase::Iterator it(s, start_line - 1, Direction::Forward);
   while (it.next() && start_line <= end_line)
     ctx.io.write_line(std::format("{:>{}}\t{}", start_line++, width, it.line));
@@ -199,7 +201,7 @@ void ClipBuffer::list_print(BEd &ctx, uint64_t start_line, uint64_t end_line) {
   ctx.prev().buffername = name;
   ctx.prev().start = start_line;
   ctx.prev().end = end_line;
-  auto s = vase::Shard::from_command("xclip -selection clipboard -o", true);
+  auto s = vase::Shard::from_command("xclip -selection clipboard -o");
   vase::Iterator it(s, start_line - 1, Direction::Forward);
   while (it.next() && start_line++ <= end_line)
     ctx.io.write_line(list_string(it.line));

src/internal/functions/extended.cc

@@ -173,21 +173,83 @@ void Function::register_extented(BEd &ctx) {
   ctx.functions.insert(
     "`",
     Function{
-      .address_kind = Function::AddressKind::None,
+      .address_kind = Function::AddressKind::Range,
       .argument_kind = Function::ArgumentKind::Ruby,
       .input_mode = Function::InputMode::None,
-      .desc = "Execute some ruby code",
+      .desc = "Execute given ruby code.",
-      .default_address = "",
+      .default_address = "0,0",
+      .accept_zero = true,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<buffer::Range>(addr_);
+        auto &arg = std::get<RubyArg>(arg_);
+        auto pre_code = "$START=" + std::to_string(addr.start)
+                        + ";$END=" + std::to_string(addr.end)
+                        + ";$BUFNAME=\"" + addr.buffername + "\"";
+        scripting::run(ctx, pre_code);
+        auto line = scripting::run(ctx, arg.cmd);
+        ctx.io.write("=> ", 3);
+        auto parser = syntax::MiniParser(
+          *ctx.languages["ruby"],
+          vase::Shard::from_string(line.data(), line.size()),
+          nullptr
+        );
+        const auto &tokens = parser.lines[0].second;
+        uint32_t cursor = 0;
+        for (const auto &token : tokens) {
+          const uint32_t start = token.start;
+          const uint32_t end = token.end;
+          if (start > line.size() || end > line.size())
+            break;
+          if (cursor < start)
+            ctx.io.write(line.data() + cursor, start - cursor);
+          ctx.io.apply(token.type);
+          ctx.io.write(line.data() + start, end - start);
+          ctx.io.reset();
+          cursor = end;
+        }
+        if (cursor < line.size())
+          ctx.io.write(line.data() + cursor, line.size() - cursor);
+        ctx.io.write_line("");
+      },
+    }
+  );
+  ctx.functions.insert(
+    "``",
+    Function{
+      .address_kind = Function::AddressKind::Range,
+      .argument_kind = Function::ArgumentKind::None,
+      .input_mode = Function::InputMode::None,
+      .desc = "Execute addressed lines as ruby code.",
+      .default_address = "1,$",
       .accept_zero = false,
       .pre_text_mode = nullptr,
       .handle = [](
-                  BEd &,
+                  BEd &ctx,
-                  const buffer::Address &,
+                  const buffer::Address &addr_,
                   vase::Shard *,
                   const Argument &,
                   std::vector<buffer::Line> *
                 ) {
-        // TODO: connect up to mruby.
+        auto &addr = std::get<buffer::Range>(addr_);
+        auto &buf = ctx.buffer(addr.buffername);
+        auto code = buf.copy(addr.start, addr.end);
+        ctx.prev().buffername = addr.buffername;
+        ctx.prev().start = addr.start;
+        ctx.prev().end = addr.end;
+        ctx.current() = {addr.buffername, addr.end};
+        auto pre_code = "$START=" + std::to_string(addr.start)
+                        + ";$END=" + std::to_string(addr.end)
+                        + ";$BUFNAME=\"" + addr.buffername + "\"";
+        scripting::run(ctx, pre_code);
+        scripting::run(ctx, vase::to_string(code));
+        vase::Shard::release(code);
       },
     }
   );
@@ -225,7 +287,7 @@ void Function::register_extented(BEd &ctx) {
               str[i - 1] = '\n';
             continue;
           }
-          if (str[i] == '$' && i < str.size() && '1' <= str[i + 1] && str[i + 1] <= '4') {
+          if (str[i] == '$' && i + 1 < str.size() && '1' <= str[i + 1] && str[i + 1] <= '4') {
             char c = str[i + 1];
             str.erase(i, 2);
             switch (c) {
@@ -432,5 +494,38 @@ void Function::register_extented(BEd &ctx) {
       }
     }
   );
+  ctx.functions.insert(
+    "lang",
+    Function{
+      .address_kind = Function::AddressKind::None,
+      .argument_kind = Function::ArgumentKind::Any,
+      .input_mode = Function::InputMode::None,
+      .desc = "Set buffer language",
+      .default_address = "",
+      .accept_zero = false,
+      .pre_text_mode = nullptr,
+      .handle = [](
+                  BEd &ctx,
+                  const buffer::Address &addr_,
+                  vase::Shard *,
+                  const Argument &arg_,
+                  std::vector<buffer::Line> *
+                ) {
+        auto &addr = std::get<std::string>(addr_);
+        auto name = std::get<std::string>(arg_);
+        const auto first = name.find_first_not_of(" \t");
+        const auto last = name.find_last_not_of(" \t");
+        if (first == std::string::npos)
+          name.clear();
+        else
+          name = name.substr(first, last - first + 1);
+        auto &buf_ = ctx.buffer(addr);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          throw ed_error("Can't set language to buffer.");
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        buf.language(ctx, name);
+      }
+    }
+  );
 }
 } // namespace bed::internal::functions

src/internal/functions/posix.cc

@@ -37,7 +37,19 @@ void Function::register_posix(BEd &ctx) {
       .desc = "Append text to a line",
       .default_address = ".",
       .accept_zero = true,
-      .pre_text_mode = nullptr,
+      .pre_text_mode = [](
+                         BEd &ctx,
+                         const buffer::Address &addr_,
+                         const Argument &
+                       ) -> std::tuple<vase::Shard *, syntax::Language *, void *> {
+        const auto &addr = std::get<buffer::Line>(addr_);
+        auto &buf_ = ctx.buffer(addr.buffername);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          return {nullptr, nullptr, nullptr};
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        void *state = syntax::state_before(buf.parse, buf.root, addr.number);
+        return {nullptr, buf.parse.lang, state};
+      },
       .handle = [](
                   BEd &ctx,
                   const buffer::Address &addr_,
@@ -47,8 +59,7 @@ void Function::register_posix(BEd &ctx) {
                 ) {
         auto addr = std::get<buffer::Line>(addr_);
         ctx.buffer(addr.buffername).append(ctx, text, addr.number);
-        vase::Shard::release(text);
+        vase::Shard::release(text); }
-      }
     }
   );
   ctx.functions.insert(
@@ -70,9 +81,7 @@ void Function::register_posix(BEd &ctx) {
         if (buf_.kind != buffer::Buffer::Kind::Generic)
           return {buf_.copy(addr.start, addr.end), nullptr, nullptr};
         auto &buf = *(buffer::GenericBuffer *)&buf_;
-        if (!buf.parse.lang)
+        void *state = syntax::state_before(buf.parse, buf.root, addr.start - 1);
-          return {buf.copy(addr.start, addr.end), nullptr, nullptr};
-        void *state = nullptr; // TODO: buf.parse.root.get_at(addr.start);
         return {buf.copy(addr.start, addr.end), buf.parse.lang, state};
       },
       .handle = [](
@@ -135,17 +144,17 @@ void Function::register_posix(BEd &ctx) {
         vase::Shard *s = nullptr;
         if (std::holds_alternative<std::filesystem::path>(arg)) {
           auto path = std::get<std::filesystem::path>(arg);
-          s = vase::Shard::from_file(path, true);
+          s = vase::Shard::from_file(path);
           buf.set_filename(path);
         } else if (std::holds_alternative<ShellArg>(arg)) {
           auto cmd = std::get<ShellArg>(arg).cmd;
           ctx.escape_command(cmd, buf.filename().string());
-          s = vase::Shard::from_command(cmd.c_str(), true);
+          s = vase::Shard::from_command(cmd.c_str());
         } else {
           auto path = buf.filename();
           if (path.empty())
             throw ed_error("Need filename.");
-          s = vase::Shard::from_file(path, true);
+          s = vase::Shard::from_file(path);
         };
         try {
           buf.load(ctx, s);
@@ -181,17 +190,17 @@ void Function::register_posix(BEd &ctx) {
         vase::Shard *s = nullptr;
         if (std::holds_alternative<std::filesystem::path>(arg)) {
           auto path = std::get<std::filesystem::path>(arg);
-          s = vase::Shard::from_file(path, true);
+          s = vase::Shard::from_file(path);
           buf.set_filename(path);
         } else if (std::holds_alternative<ShellArg>(arg)) {
           auto cmd = std::get<ShellArg>(arg).cmd;
           ctx.escape_command(cmd, buf.filename().string());
-          s = vase::Shard::from_command(cmd.c_str(), true);
+          s = vase::Shard::from_command(cmd.c_str());
         } else {
           auto path = buf.filename();
           if (path.empty())
             throw ed_error("Need filename.");
-          s = vase::Shard::from_file(path, true);
+          s = vase::Shard::from_file(path);
         };
         try {
           buf.load(ctx, s);
@@ -291,7 +300,21 @@ void Function::register_posix(BEd &ctx) {
       .desc = "Insert text before a line",
       .default_address = ".",
       .accept_zero = true,
-      .pre_text_mode = nullptr,
+      .pre_text_mode = [](
+                         BEd &ctx,
+                         const buffer::Address &addr_,
+                         const Argument &
+                       ) -> std::tuple<vase::Shard *, syntax::Language *, void *> {
+        auto addr = std::get<buffer::Line>(addr_);
+        if (addr.number)
+          addr.number--;
+        auto &buf_ = ctx.buffer(addr.buffername);
+        if (buf_.kind != buffer::Buffer::Kind::Generic)
+          return {nullptr, nullptr, nullptr};
+        auto &buf = *(buffer::GenericBuffer *)&buf_;
+        void *state = syntax::state_before(buf.parse, buf.root, addr.number);
+        return {nullptr, buf.parse.lang, state};
+      },
       .handle = [](
                   BEd &ctx,
                   const buffer::Address &addr_,
@@ -303,8 +326,7 @@ void Function::register_posix(BEd &ctx) {
         if (addr.number)
           addr.number--;
         ctx.buffer(addr.buffername).append(ctx, text, addr.number);
-        vase::Shard::release(text);
+        vase::Shard::release(text); }
-      }
     }
   );
   ctx.functions.insert(
@@ -394,8 +416,7 @@ void Function::register_posix(BEd &ctx) {
         auto addr = std::get<buffer::Range>(addr_);
         auto arg = std::get<buffer::Line>(arg_);
         if (arg.buffername == addr.buffername
-            && addr.start <= arg.number
+            && arg.number >= addr.start && arg.number < addr.end)
-            && addr.end < arg.number)
           throw ed_error("Can't move lines within themselves.");
         auto text = ctx.buffer(addr.buffername).copy(addr.start, addr.end);
         ctx.mark(252, arg);
@@ -567,18 +588,18 @@ void Function::register_posix(BEd &ctx) {
         vase::Shard *s = nullptr;
         if (std::holds_alternative<std::filesystem::path>(arg)) {
           auto path = std::get<std::filesystem::path>(arg);
-          s = vase::Shard::from_file(path, true);
+          s = vase::Shard::from_file(path);
           if (buf.filename().empty())
             buf.set_filename(path);
         } else if (std::holds_alternative<ShellArg>(arg)) {
           auto cmd = std::get<ShellArg>(arg).cmd;
           ctx.escape_command(cmd, buf.filename().string());
-          s = vase::Shard::from_command(cmd.c_str(), true);
+          s = vase::Shard::from_command(cmd.c_str());
         } else {
           auto path = buf.filename();
           if (path.empty())
             throw ed_error("Need filename.");
-          s = vase::Shard::from_file(path, true);
+          s = vase::Shard::from_file(path);
         };
         try {
           buf.append(ctx, s, addr.number);
@@ -735,6 +756,7 @@ void Function::register_posix(BEd &ctx) {
           vase::Shard::release(text);
           throw;
         }
+        buf.saved_hook();
         if (!ctx.suppress_mode)
           ctx.io.write(std::format("{}\n", text ? text->length + 1 : 0));
       }

src/internal/scripting/ruby.cc

@@ -0,0 +1,149 @@
+#include "internal/scripting/ruby.h"
+#include "bed.h"
+
+namespace bed::internal::scripting {
+static mrb_value mrb_bed_exit(mrb_state *mrb, mrb_value) {
+  mrb_raise(mrb, E_RUNTIME_ERROR, "Use `handle(\"q\")` to quit.");
+  return mrb_nil_value();
+}
+
+static void raise_fatal(mrb_state *mrb, const fatal_error &e) {
+  struct RClass *klass = mrb_class_get(mrb, "FatalError");
+  mrb_value exc = mrb_exc_new_str(mrb, klass, mrb_str_new_cstr(mrb, e.what()));
+  mrb_iv_set(mrb, exc, mrb_intern_lit(mrb, "@code"), mrb_fixnum_value(e.code));
+  mrb_exc_raise(mrb, exc);
+}
+
+static mrb_value mrb_bed_handle(mrb_state *mrb, mrb_value) {
+  auto &ctx = *(BEd *)mrb->ud;
+  const char *command;
+  mrb_int len;
+  mrb_get_args(mrb, "s", &command, &len);
+  std::string_view cmd(command, len);
+  try {
+    ctx.handle(cmd, false);
+  } catch (const ed_error &e) {
+    mrb_raise(mrb, mrb_class_get(mrb, "EdError"), e.what());
+  } catch (const fatal_error &f) {
+    raise_fatal(mrb, f);
+  }
+  return mrb_nil_value();
+}
+
+static mrb_value hash_get(mrb_state *mrb, mrb_value hash, const char *name) {
+  if (mrb_nil_p(hash))
+    return mrb_nil_value();
+  return mrb_hash_get(mrb, hash, mrb_symbol_value(mrb_intern_cstr(mrb, name)));
+}
+
+static functions::Function::AddressKind parse_address_kind(mrb_state *mrb, mrb_value value) {
+  if (mrb_nil_p(value))
+    return functions::Function::AddressKind::None;
+  if (!mrb_symbol_p(value))
+    mrb_raise(mrb, E_TYPE_ERROR, "address must be a Symbol");
+  auto name = mrb_sym_name(mrb, mrb_symbol(value));
+  if (strcmp(name, "none") == 0)
+    return functions::Function::AddressKind::None;
+  if (strcmp(name, "line") == 0)
+    return functions::Function::AddressKind::Line;
+  if (strcmp(name, "range") == 0)
+    return functions::Function::AddressKind::Range;
+  mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid address type: :%s", name);
+  return functions::Function::AddressKind::None;
+}
+
+static mrb_value mrb_bed_register(mrb_state *mrb, mrb_value) {
+  auto &ctx = *(BEd *)mrb->ud;
+  mrb_sym r_cmd_name;
+  mrb_value proc;
+  mrb_value opts = mrb_nil_value();
+  mrb_get_args(mrb, "n&|H", &r_cmd_name, &proc, &opts);
+  mrb_int cmd_name_len;
+  const char *name = mrb_sym_name_len(mrb, r_cmd_name, &cmd_name_len);
+  std::string_view cmd_name(name, cmd_name_len);
+  std::string desc;
+  mrb_value r_desc = hash_get(mrb, opts, "desc");
+  if (mrb_string_p(r_desc))
+    desc.assign(RSTRING_PTR(r_desc), RSTRING_LEN(r_desc));
+  std::string default_address;
+  mrb_value r_default_address = hash_get(mrb, opts, "default");
+  if (mrb_string_p(r_default_address))
+    default_address.assign(RSTRING_PTR(r_default_address), RSTRING_LEN(r_default_address));
+  ctx.functions.insert(
+    cmd_name,
+    functions::Function{
+      .address_kind = parse_address_kind(mrb, hash_get(mrb, opts, "address")),
+      .argument_kind = functions::Function::ArgumentKind::None,
+      .input_mode = functions::Function::InputMode::None,
+      .desc = desc,
+      .default_address = default_address,
+      .accept_zero = true,
+      .pre_text_mode = nullptr,
+      .handle = [b = Block(mrb, proc)](
+                  BEd &,
+                  const buffer::Address &,
+                  vase::Shard *,
+                  const functions::Function::Argument &,
+                  std::vector<buffer::Line> *
+                ) {
+        b.call();
+      }
+    }
+  );
+  return mrb_nil_value();
+}
+
+static mrb_value mrb_bed_unregister(mrb_state *mrb, mrb_value) {
+  auto &ctx = *(BEd *)mrb->ud;
+  mrb_sym r_cmd_name;
+  mrb_get_args(mrb, "n", &r_cmd_name);
+  mrb_int cmd_name_len;
+  const char *name = mrb_sym_name_len(mrb, r_cmd_name, &cmd_name_len);
+  std::string_view cmd_name(name, cmd_name_len);
+  ctx.functions.remove(cmd_name);
+  return mrb_nil_value();
+}
+
+void register_basic(BEd &ctx) {
+  auto mrb = ctx.mrb.state;
+  auto *bed_error =
+    mrb_define_class(mrb, "EdError", mrb_exc_get_id(mrb, MRB_ERROR_SYM(RuntimeError)));
+  mrb_define_class(mrb, "FatalError", bed_error);
+  mrb_define_method(mrb, mrb->kernel_module, "exit", mrb_bed_exit, MRB_ARGS_NONE());
+  mrb_define_method(mrb, mrb->kernel_module, "handle", mrb_bed_handle, MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, mrb->kernel_module, "register", mrb_bed_register, MRB_ARGS_REQ(1) | MRB_ARGS_OPT(1) | MRB_ARGS_BLOCK());
+  mrb_define_method(mrb, mrb->kernel_module, "unregister", mrb_bed_unregister, MRB_ARGS_REQ(1));
+}
+
+std::string run(BEd &ctx, const std::string &str) {
+  mrb_state *mrb = ctx.mrb.state;
+  mrb_value result = mrb_load_nstring(mrb, str.data(), str.size());
+  if (!mrb->exc) {
+    mrb_value inspected = mrb_funcall(mrb, result, "inspect", 0);
+    std::string output(RSTRING_PTR(inspected), RSTRING_LEN(inspected));
+    return output;
+  }
+  mrb_value exc = mrb_obj_value(mrb->exc);
+  mrb_value msg = mrb_funcall(mrb, exc, "message", 0);
+  std::string error;
+  if (mrb_string_p(msg))
+    error.assign(RSTRING_PTR(msg), RSTRING_LEN(msg));
+  auto *fatal_class = mrb_class_get(mrb, "FatalError");
+  if (mrb_obj_is_kind_of(mrb, exc, fatal_class)) {
+    mrb_value code =
+      mrb_iv_get(mrb, exc, mrb_intern_lit(mrb, "@code"));
+    mrb->exc = nullptr;
+    int c = 1;
+    if (mrb_fixnum_p(code))
+      c = mrb_fixnum(code);
+    throw fatal_error(error, c);
+  }
+  auto *ed_class = mrb_class_get(mrb, "EdError");
+  if (mrb_obj_is_kind_of(mrb, exc, ed_class)) {
+    mrb->exc = nullptr;
+    throw ed_error(error);
+  }
+  mrb->exc = nullptr;
+  throw ed_error("Ruby Exception: " + error);
+}
+} // namespace bed::internal::scripting

src/internal/syntax/iterator.cc

@@ -2,19 +2,11 @@
 
 namespace bed::internal::syntax {
 Iterator::Iterator(uint64_t target, ParserSnapshot p, vase::Shard *vase)
-    : snap(p) {
+    : snap(p), at(target) {
-  uint64_t offset;
+  at = target;
-  TreeCursor c = TreeCursor(*p.lang, p.root, target, &offset);
+  if (snap.lang)
-  at = target - offset;
+    state = ParseState::state_before(*snap.lang, snap.root, vase, at);
-  state = p.lang->copy(c.leaf->state);
   it = vase::Iterator(vase, at, Direction::Forward);
-  while (at < target) {
-    it->next();
-    tokens.clear();
-    events.clear();
-    p.lang->parse(&state, it->line, at == 0, &tokens, &events);
-    at++;
-  }
 }
 
 Iterator::~Iterator() {
@@ -46,6 +38,8 @@ Iterator &Iterator::operator=(Iterator &&other) {
 }
 
 void Iterator::next() {
+  if (!state)
+    return;
   it->next();
   tokens.clear();
   events.clear();

src/internal/syntax/miniparser.cc

@@ -8,7 +8,7 @@ MiniParser::MiniParser(Language &lang, vase::Shard *vase, void *initial_state)
   void *state = lang.copy(start_state);
   std::vector<io::Token> tokens;
   std::vector<ParseEvent> events;
-  const uint64_t count = vase ? vase->lines + 1 : 0;
+  const uint64_t count = vase ? vase->lines + 1 : 1;
   lines.reserve(count);
   for (uint64_t i = 0; i < count; ++i) {
     it.next();

src/internal/syntax/parser.cc

@@ -22,6 +22,12 @@ void release(ParserSnapshot &snap) {
   snap.root = nullptr;
 }
 
+void *state_before(const ParserSnapshot &snap, vase::Shard *vase, uint64_t line) {
+  if (!snap.lang)
+    return nullptr;
+  return ParseState::state_before(*snap.lang, snap.root, vase, line);
+}
+
 uint64_t next_closing(const ParserSnapshot &snap, uint64_t line) {
   if (!snap.root || !snap.lang)
     return line + 10;

src/internal/syntax/parser_state.cc

@@ -108,7 +108,7 @@ ParseState *ParseState::splice(
     void *state = lang.none_state();
     std::vector<io::Token> tokens;
     std::vector<ParseEvent> events;
-    ParsePieceBuilder builder(lang, 0);
+    ParsePieceBuilder builder(lang, 0, state);
     for (uint64_t at = 0; at < final; ++at) {
       it.next();
       tokens.clear();
@@ -136,7 +136,7 @@ ParseState *ParseState::splice(
   uint64_t end_extra;
   TreeCursor c = TreeCursor(lang, root, end_in_tree, &end_extra);
   uint64_t end_in_vase = line + final;
-  ParsePieceBuilder builder(lang, at);
+  ParsePieceBuilder builder(lang, at, state);
   while (at < end_in_vase + end_extra) {
     it.next();
     tokens.clear();
@@ -192,4 +192,28 @@ ParseState *ParseState::concat(Language &lang, ParseState *a, ParseState *b) {
   }
   return balance(lang, new ParseStateBranch(a, b));
 }
+
+void *ParseState::state_before(Language &lang, ParseState *root, vase::Shard *vase, uint64_t line) {
+  uint64_t offset;
+  uint64_t at;
+  void *state;
+  if (!root) {
+    at = 0;
+    state = lang.none_state();
+  } else {
+    TreeCursor c = TreeCursor(lang, root, line, &offset);
+    at = line - offset;
+    state = lang.copy(c.leaf->state);
+  }
+  vase::Iterator it(vase, at, Direction::Forward);
+  std::vector<io::Token> tokens;
+  std::vector<ParseEvent> events;
+  for (; at < line; ++at) {
+    it.next();
+    tokens.clear();
+    events.clear();
+    lang.parse(&state, it.line, at == 0, &tokens, &events);
+  }
+  return state;
+}
 } // namespace bed::internal::syntax

src/internal/syntax/ruby/parse.cc

@@ -35,71 +35,83 @@ inline uint8_t utf8_codepoint_width(unsigned char c) {
 }
 
 bool handle_escapes(RubyParser &p, std::vector<io::Token> *tokens, uint32_t &start, bool string = true) {
-  if (p.peek() == '\\') {
+  if (p.peek() != '\\')
-    if (string)
+    return false;
-      tokens->push_back({start, p.i, io::Token::String});
+  if (!(p.current().flags & RubyState::RubyInternalState::ALLOW_ESCAPE)) {
-    else
-      tokens->push_back({start, p.i, io::Token::Regexp});
-    start = p.i;
     p.advance();
-    if (p.peek() == 'x') {
+    if (p.peek() != '\'' && p.peek() != '\\')
-      p.advance();
+      return false;
-      if (is_hex(p.peek()))
+    if (string)
-        p.advance();
+      tokens->push_back({start, p.i - 1, io::Token::String});
-      if (is_hex(p.peek()))
+    else
-        p.advance();
+      tokens->push_back({start, p.i - 1, io::Token::Regexp});
-    } else if (p.peek() == 'u') {
+    p.advance();
-      p.advance();
+    tokens->push_back({p.i - 2, p.i, io::Token::Escape});
-      if (p.peek() == '{') {
-        p.advance();
-        while (p.peek() != '}' && p.peek() != '\0')
-          p.advance();
-        if (p.peek() == '}')
-          p.advance();
-      } else {
-        if (is_hex(p.peek()))
-          p.advance();
-        if (is_hex(p.peek()))
-          p.advance();
-        if (is_hex(p.peek()))
-          p.advance();
-        if (is_hex(p.peek()))
-          p.advance();
-      }
-    } else if ('0' <= p.peek() && p.peek() <= '7') {
-      p.advance();
-      if ('0' <= p.peek() && p.peek() <= '7')
-        p.advance();
-      if ('0' <= p.peek() && p.peek() <= '7')
-        p.advance();
-    } else if (p.peek() == 'c') {
-      p.advance();
-      if (p.peek() != '\\')
-        p.advance();
-    } else if (p.peek() == 'M' || p.peek() == 'C') {
-      p.advance();
-      if (p.peek() == '-') {
-        p.advance();
-        if (p.peek() != '\\')
-          p.advance();
-      }
-    } else if (p.peek() == 'N') {
-      p.advance();
-      if (p.peek() == '{') {
-        p.advance();
-        while (p.peek() != '}' && p.peek() != '\0')
-          p.advance();
-        if (p.peek() == '}')
-          p.advance();
-      }
-    } else {
-      p.advance();
-    }
-    tokens->push_back({start, p.i, io::Token::Escape});
     start = p.i;
     return true;
   }
-  return false;
+  if (string)
+    tokens->push_back({start, p.i, io::Token::String});
+  else
+    tokens->push_back({start, p.i, io::Token::Regexp});
+  start = p.i;
+  p.advance();
+  if (p.peek() == 'x') {
+    p.advance();
+    if (is_hex(p.peek()))
+      p.advance();
+    if (is_hex(p.peek()))
+      p.advance();
+  } else if (p.peek() == 'u') {
+    p.advance();
+    if (p.peek() == '{') {
+      p.advance();
+      while (p.peek() != '}' && p.peek() != '\0')
+        p.advance();
+      if (p.peek() == '}')
+        p.advance();
+    } else {
+      if (is_hex(p.peek()))
+        p.advance();
+      if (is_hex(p.peek()))
+        p.advance();
+      if (is_hex(p.peek()))
+        p.advance();
+      if (is_hex(p.peek()))
+        p.advance();
+    }
+  } else if ('0' <= p.peek() && p.peek() <= '7') {
+    p.advance();
+    if ('0' <= p.peek() && p.peek() <= '7')
+      p.advance();
+    if ('0' <= p.peek() && p.peek() <= '7')
+      p.advance();
+  } else if (p.peek() == 'c') {
+    p.advance();
+    if (p.peek() != '\\')
+      p.advance();
+  } else if (p.peek() == 'M' || p.peek() == 'C') {
+    p.advance();
+    if (p.peek() == '-') {
+      p.advance();
+      if (p.peek() != '\\')
+        p.advance();
+    }
+  } else if (p.peek() == 'N') {
+    p.advance();
+    if (p.peek() == '{') {
+      p.advance();
+      while (p.peek() != '}' && p.peek() != '\0')
+        p.advance();
+      if (p.peek() == '}')
+        p.advance();
+    }
+  } else {
+    p.advance();
+  }
+  tokens->push_back({start, p.i, io::Token::Escape});
+  start = p.i;
+  return true;
 };
 
 bool handle_heredoc(RubyParser &p, std::vector<io::Token> *tokens, std::vector<ParseEvent> *events) {
@@ -668,6 +680,7 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
     p.current().delim_start = '\'';
     p.current().delim_end = '\'';
     p.current().flags &= ~RubyState::RubyInternalState::ALLOW_INTERPOLATION;
+    p.current().flags &= ~RubyState::RubyInternalState::ALLOW_ESCAPE;
     p.advance();
     return false;
   }
@@ -678,6 +691,7 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
     p.current().delim_start = '"';
     p.current().delim_end = '"';
     p.current().flags |= RubyState::RubyInternalState::ALLOW_INTERPOLATION;
+    p.current().flags |= RubyState::RubyInternalState::ALLOW_ESCAPE;
     p.advance();
     return false;
   }
@@ -703,6 +717,7 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
     char delim_start = '\0';
     char delim_end = '\0';
     bool allow_interp = true;
+    bool allow_escape = true;
     int prefix_len = 1;
     bool is_regexp = false;
     switch (type) {
@@ -716,6 +731,7 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
     case 'I':
     case 'W':
       allow_interp = true;
+      allow_escape = true;
       prefix_len = 2;
       break;
     case 'w':
@@ -723,10 +739,12 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
     case 'i':
     case 's':
       allow_interp = false;
+      allow_escape = false;
       prefix_len = 2;
       break;
     default:
       allow_interp = true;
+      allow_escape = true;
       prefix_len = 1;
       break;
     }
@@ -768,6 +786,8 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
     p.current().delim_end = delim_end;
     if (allow_interp)
       p.current().flags |= RubyState::RubyInternalState::ALLOW_INTERPOLATION;
+    if (allow_escape)
+      p.current().flags |= RubyState::RubyInternalState::ALLOW_ESCAPE;
     p.current().lit_brace_level = 1;
     p.advance(prefix_len + 1);
     return false;
@@ -782,11 +802,6 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
       p.ending = false;
     p.advance();
     return false;
-  case '\0':
-    if (p.ending)
-      p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
-    p.advance();
-    return false;
   default:
     if ('0' <= p.peek() && p.peek() <= '9') {
       p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
@@ -981,6 +996,11 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
             | RubyState::RubyInternalState::DEF_NAME;
           return false;
         }
+        if (j > 3 && p.peek_str(3) == "to_") {
+          p.current().flags &= ~RubyState::RubyInternalState::EXPECTING_EXPRESSION;
+          tokens->push_back({p.i, p.i + j, io::Token::Function});
+          p.advance(j);
+        }
         uint32_t start = p.i;
         if (p.peek(j) == ':') {
           p.advance(j);
@@ -1008,8 +1028,9 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
             return false;
           if (p.peek(j) == '&'
               || p.peek(j) == '%'
-              || p.peek(j) == ':') {
+              || p.peek(j) == ':'
-            if (p.peek(j + 1) == ' ' || p.peek(j + 1) == '>')
+              || p.peek(j) == '?') {
+            if (p.peek(j + 1) == ' ' || p.peek(j + 1) == '\0')
               return false;
           } else if (p.peek(j) == '-') {
             if (p.peek(j + 1) != '>')
@@ -1025,7 +1046,6 @@ bool handle_syntax(RubyParser &p, std::vector<io::Token> *tokens, std::vector<Pa
             || p.peek(j) == '*'
             || p.peek(j) == '/'
             || p.peek(j) == '='
-            || p.peek(j) == '?'
             || p.peek(j) == '|'
             || p.peek(j) == '^'
             || p.peek(j) == '<'
@@ -1061,7 +1081,7 @@ void ruby_parse(
   std::vector<ParseEvent> *events
 ) {
   RubyParser p(v_state, line);
-  while (p.i <= p.len()) {
+  while (p.i < p.len()) {
     p.op_last = p.set_op_last;
     p.set_op_last = false;
     if (p.current().state == RubyState::RubyInternalState::END)
@@ -1099,6 +1119,13 @@ void ruby_parse(
       return;
     if (!handle_syntax(p, tokens, events))
       p.current().flags &= ~RubyState::RubyInternalState::NEWLINE;
+    if (p.peek() == '\0') {
+      if (p.ending)
+        p.current().flags |= RubyState::RubyInternalState::EXPECTING_EXPRESSION;
+      p.advance();
+      p.current().flags &= ~RubyState::RubyInternalState::NEWLINE;
+      break;
+    }
     continue;
   }
   if (p.ending)

src/internal/ui/text_mode/text_mode.cc

@@ -2,6 +2,8 @@
 #include "bed.h"
 
 namespace bed::internal::ui::text_mode {
+// TODO: make this into a proper layout engine, in order to avoid so many expensive calculations repeatedly.
+
 template <typename F>
 static void for_each_cluster(std::string_view s, F &&f) {
   size_t cluster_start = 0;
@@ -204,11 +206,13 @@ std::pair<vase::Shard *, bool> TextMode::run_terminal() {
             }
             vase::Range r = {last, cursor};
             vase = vase::erase(vase, r);
-            if (cursor.row == last.row) {
+            if (parser) {
-              parser->dirty(vase, cursor.row, 1);
+              if (cursor.row == last.row) {
-            } else {
+                parser->dirty(vase, cursor.row, 1);
-              parser->erase(vase, cursor.row, 1);
+              } else {
-              parser->dirty(vase, last.row, 1);
+                parser->erase(vase, cursor.row, 1);
+                parser->dirty(vase, last.row, 1);
+              }
             }
             cursor = last;
           }
@@ -222,10 +226,12 @@ std::pair<vase::Shard *, bool> TextMode::run_terminal() {
             }
           }
           vase = vase::insert(&bed.append, vase, &cursor, '\n');
-          parser->insert(vase, cursor.row - 1, 1);
+          if (parser)
+            parser->insert(vase, cursor.row - 1, 1);
         } else {
           vase = vase::insert(&bed.append, vase, &cursor, res.text.data(), res.text.size());
-          parser->dirty(vase, cursor.row, 1);
+          if (parser)
+            parser->dirty(vase, cursor.row, 1);
         }
         break;
       }
@@ -233,11 +239,13 @@ std::pair<vase::Shard *, bool> TextMode::run_terminal() {
     case io::KeyEvent::KeyType::PASTE: {
       auto lines = std::count(res.text.begin(), res.text.end(), '\n');
       vase = vase::insert(&bed.append, vase, &cursor, res.text.data(), res.text.size());
-      if (lines) {
+      if (parser) {
-        parser->insert(vase, cursor.row - lines, lines);
+        if (lines) {
-        parser->dirty(vase, cursor.row - lines, 1);
+          parser->insert(vase, cursor.row - lines, lines);
-      } else {
+          parser->dirty(vase, cursor.row - lines, 1);
-        parser->dirty(vase, cursor.row, 1);
+        } else {
+          parser->dirty(vase, cursor.row, 1);
+        }
       }
     } break;
     case io::KeyEvent::KeyType::SPECIAL:
@@ -302,9 +310,11 @@ std::pair<vase::Shard *, bool> TextMode::run_terminal() {
         }
         vase::Range r = {cursor, next};
         vase = vase::erase(vase, r);
-        if (cursor.row != next.row)
+        if (parser) {
-          parser->erase(vase, cursor.row + 1, 1);
+          if (cursor.row != next.row)
-        parser->dirty(vase, cursor.row, 1);
+            parser->erase(vase, cursor.row + 1, 1);
+          parser->dirty(vase, cursor.row, 1);
+        }
       }
       break;
     }

src/internal/vase/shard.cc

@@ -202,7 +202,7 @@ Shard *Shard::build(Shard **pieces, uint64_t lo, uint64_t hi) {
   return node;
 }
 
-Shard *Shard::from_command(const char *cmd, bool posix_ending) {
+Shard *Shard::from_command(const char *cmd) {
   auto o = new OriginalStorage("/tmp");
   int dest_fd = o->fd;
   if (dest_fd == -1) {
@@ -278,23 +278,21 @@ Shard *Shard::from_command(const char *cmd, bool posix_ending) {
     io::IO::enable_raw();
     return nullptr;
   }
-  if (posix_ending) {
+  if (ending[1] == '\n') {
-    if (ending[1] == '\n') {
+    Petal *last = (Petal *)pieces.back();
-      Petal *last = (Petal *)pieces.back();
+    last->lines--;
-      last->lines--;
+    last->length--;
-      last->length--;
+    if (last->length == 0) {
-      if (last->length == 0) {
+      Shard::release(last);
-        Shard::release(last);
+      pieces.pop_back();
-        pieces.pop_back();
+      last = nullptr;
-        last = nullptr;
+      if (!pieces.empty())
-        if (!pieces.empty())
+        last = (Petal *)pieces.back();
-          last = (Petal *)pieces.back();
+      else
-        else
+        return nullptr;
-          return nullptr;
-      }
-      if (last && ending[0] == '\r')
-        last->length--;
     }
+    if (last && ending[0] == '\r')
+      last->length--;
   }
   o->initialize();
   io::IO::enable_raw();
@@ -303,7 +301,7 @@ Shard *Shard::from_command(const char *cmd, bool posix_ending) {
   return build(pieces.data(), 0, pieces.size());
 }
 
-Shard *Shard::from_file(const std::filesystem::path &path, bool posix_ending) {
+Shard *Shard::from_file(const std::filesystem::path &path) {
   auto o = new OriginalStorage("/tmp");
   int dest_fd = o->fd;
   if (dest_fd == -1) {
@@ -313,10 +311,10 @@ Shard *Shard::from_file(const std::filesystem::path &path, bool posix_ending) {
   int src_fd = open(path.c_str(), O_RDONLY);
   if (src_fd == -1) {
     delete o;
-    return nullptr;
+    throw ed_error("Couldn't open file.");
   }
   uint64_t total = std::filesystem::file_size(path);
-  if (posix_ending && total > 0) {
+  if (total > 0) {
     char last;
     if (pread(src_fd, &last, 1, (off_t)(total - 1)) != 1) {
       delete o;
@@ -381,7 +379,7 @@ Shard *Shard::from_file(const std::filesystem::path &path, bool posix_ending) {
   return build(pieces.data(), 0, pieces.size());
 }
 
-Shard *Shard::from_string(const char *data, uint64_t len, bool posix_ending) {
+Shard *Shard::from_string(const char *data, uint64_t len) {
   auto o = new OriginalStorage("/tmp");
   int dest_fd = o->fd;
   if (dest_fd == -1 || data == nullptr) {
@@ -389,7 +387,7 @@ Shard *Shard::from_string(const char *data, uint64_t len, bool posix_ending) {
     return nullptr;
   }
   uint64_t total = len;
-  if (posix_ending && total > 0) {
+  if (total > 0) {
     if (data[total - 1] == '\n') {
       total--;
       if (total > 0 && data[total - 1] == '\r')

src/internal/vase/vase.cc

@@ -182,8 +182,6 @@ Shard *insert(AppendStorage *ap, Shard *root, Shard *text, uint64_t line) {
     Shard::retain(text);
     return text;
   }
-  if (!text)
-    return root;
   if (line > root->lines + 1)
     throw ed_error("line out of range");
   Shard::retain(text);