Simple arl-mode plugin for Emacs

That's the real purpose of this module; it's not really generating an
AST since ARL's syntax isn't tree like whatsoever.

The next stage will be something closer to an AST, in the sense we'll
be introducing:
- Syntactical analysis
- Type Checking

.dir-locals.el

@@ -1,6 +1,6 @@
 ;;; Directory Local Variables            -*- no-byte-compile: t -*-
 ;;; For more information see (info "(emacs) Directory Variables")
 
-((nil      . ((compile-command . "make MODE=debug -k")
+((nil      . ((compile-command . "make -k MODE=debug examples")
               (+license/license-choice . "MIT License")))
  (c-mode   . ((mode . clang-format))))

Makefile

@@ -3,13 +3,13 @@ CC=cc
 DIST=build
 OUT=$(DIST)/arl.out
 
-MODULES=. lib parser
-UNITS=main lib/vec lib/sv parser/ast parser/parser
+MODULES=$(shell cd include/arl; find . -type 'd' -printf "%f\n")
+UNITS=main cli lib/vec lib/sv lexer/token lexer/lexer
 OBJECTS:=$(patsubst %,$(DIST)/%.o, $(UNITS))
 
 LDFLAGS=
-GFLAGS=-Wall -Wextra -Wpedantic -std=c23 -I./src/
-DFLAGS=-ggdb -fsanitize=address -fsanitize=undefined
+GFLAGS=-Wall -Wextra -Wpedantic -std=c23 -I./include/
+DFLAGS=-ggdb -fsanitize=address -fsanitize=undefined -DVERBOSE_LOGS=1
 RFLAGS=-O3
 
 MODE=release
@@ -26,7 +26,7 @@ DEPDIR=$(DIST)/deps
 $(OUT): $(OBJECTS) | $(DIST)
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
-$(DIST)/%.o: src/arl/%.c | $(DIST) $(DEPDIR)
+$(DIST)/%.o: src/%.c | $(DIST) $(DEPDIR)
 	$(CC) $(CFLAGS) $(DEPFLAGS) $(DEPDIR)/$*.d -c -o $@ $<
 
 $(DIST):
@@ -35,7 +35,11 @@ $(DIST):
 $(DEPDIR):
 	mkdir -p $(patsubst %,$(DEPDIR)/%, $(MODULES))
 
-.PHONY: run clean
+clangd: compile_commands.json
+compile_commands.json: Makefile
+	bear -- $(MAKE) -B MODE=debug
+
+.PHONY: run clean examples
 ARGS=
 run: $(OUT)
 	./$^ $(ARGS)
@@ -43,5 +47,9 @@ run: $(OUT)
 clean:
 	rm -rf $(DIST)
 
+examples: $(OUT)
+	@echo "Example: Hello World"
+	./$^ examples/hello-world.arl
+
 DEPS:=$(patsubst %,$(DEPDIR)/%.d, $(UNITS))
 include $(wildcard $(DEPS))

README

@@ -6,13 +6,12 @@
 │ /_/   \_\_| \_\_____| │
 └───────────────────────┘
 
-Similar to Forth.  Compiles to C.
-Native speed with simple semantics.
+Similar to Forth.
 
 -----
 Goals
 -----
-- Complete operational transpiler to C
+- Complete operational transpiler, with C as a provisional working target
 - Ability to reuse compiled code (as object code) in top level ARL code.
 - Static type system with informative errors
 
@@ -44,3 +43,12 @@ $ make DIST=<folder>
 
 Similarly, the general flags used in the C compiler may be set via the CFLAGS
 variable, with linking arguments set via the LDFLAGS variable.
+
+------------------
+Usage instructions
+------------------
+Once built, simply use the built binary like so:
+$ ./build/arl.out <filename>
+
+Alternatively, you can run the examples automatically via the Makefile:
+$ make examples

arl.org

@@ -1,69 +1,64 @@
 #+title: ARL - Issue tracker
 #+date: 2026-01-23
+#+filetags: arl
 
 * TODO Write a minimum working transpiler
 We need to be able to compile the following file:
 [[file:examples/hello-world.arl]].  All it does is print "Hello,
 world!".  Should be relatively straightforward.
+** Stages
+We need the following stages in our MVP transpiler:
+- Source code reading (read bytes from a file)
+- Parse raw bytes into tokens (Lexer)
+- Interpret tokens into a classical AST (Parser)
+- Stack effect and type analysis of the AST for soundness
+- Translate AST into C code (Codegen)
+- Compile C code into native executable (Target)
+
+It's a Eulerian Path from the source code to the native executable.
 ** DONE Read file
-** DONE Parser
-** TODO Intermediate representation (Virtual Machine)
-[[file:src/arl/vm/]]
+** DONE Lexer
+[[file:src/lexer/]]
+[[file:include/arl/lexer/]]
+** WIP Parser
+[[file:src/parser/]]
+[[file:include/arl/parser/]]
 
-Before we get into generating C code and then compiling it, it might
-be worth translating the parsed ARL code into a generic IR.
+We need to generate some form of AST from the token stream.  This
+should be a little more advanced than our initial stream,
+distinguishing between
+- Literal values
+- Primitive calls
+- References to otherwise undefined words (may be defined through
+  import or later on)
+** TODO Stack effect/type analysis
+[[file:src/analysis/]]
+[[file:include/arl/analysis/]]
 
-The IR should be much more primitive in its semantics, and force clear
-requirements of the platform we're compiling to.  This way, at the
-code generator stage we can figure out:
-- what can we reasonably use from the target platform to satisfy
-  requirements?
-- what do we need to hand-roll on the target in order to make this
-  work?
+Given the AST, we need to verify the soundness of it with regards to
+types and the stack.  We have this idea of "stack effects" attached to
+every node in the AST; literals push values onto the stack and pop
+nothing, while operations may pop some operands and push some values.
 
-Essentially, we want to write a virtual machine, and translate ARL
-code into bytecode for that VM.  Goals:
-- Easier to optimise IR bytecode than the AST of our original program
-- Easier to imagine translations from that IR bytecode into target
-  platform code
-*** TODO Minimal IR representation
-We need the following clear items in our IR:
-- Static type values
-- Static type variables (possible DeBrujin numbering or other such
-  mechanism to abstract naming away and leave it to the target to
-  generate effectively)
-- Strongly typed primitive operators (numeric, strings, I/O) with
-  packed arguments
+We need a way to:
+- Codify the stack effects of each type of AST node
+- Infer the total stack effect from a sequence of nodes
 
-Read about [[https://en.wikipedia.org/wiki/Three-address_code][TAC]].
-*** TODO IR Compiler
-We should have a rough grouping between AST objects and this IR.  As
-ARL is Forth-like, we can use the stack semantics to generate this IR
-as we walk the AST in a linear manner.
-
-Consider the following ARL code:
-#+begin_src text
-34 35 +
-#+end_src
-
-When we walk through this code:
-- 34 (an integer) is pushed onto the stack
-- 35 (an integer) is pushed onto the stack
-- + is encountered
-  - Pop two values off the stack and verify their type against the
-    contract for "+" (something like (-> i32 i32 i32))
-  - Generate IR, something like ~prim-add(34, 35)~
-*** TODO Consider optimisers
-Certainly we should perform optimisations on the IR itself before
-passing it over to the code generator.  Currently we haven't got much
-in the way of optimisations to consider, but it may be worth
-considering.
+These stack effects work in tandem with our type analysis.  Stack
+shape analysis tells us what operands are being fed into primitives,
+while the type analysis will tell us if the operands are well formed
+for the primitives.
 ** TODO Code generator
-[[file:src/arl/target-c/]]
+[[file:src/codegen/]]
+[[file:include/arl/codegen/]]
 
-This should take the IR translated from the AST generated by the
-parser, and write equivalent C code.
+This should take the AST generated by the parser (which should already
+have been analysed), and write equivalent C code.
+** TODO Target compilation
+[[file:src/target/]]
+[[file:include/arl/target/]]
 
-After we've generated the C code, we need to call a C compiler on it
-to generate a binary.  GCC and Clang allow passing source code through
-stdin, so we don't even need to write to disk first which is nice.
+=gcc= and =clang= take C code via /stdin/, so we don't need to write
+the C code to disk - we can just leave it as a buffer of bytes.  So
+we'll call the compilers and feed the generated code from the previous
+stage into it via stdin.

examples/hello-world.arl

@@ -1 +1 @@
-"Hello, world!" println
+"Hello, world!\n" puts

extensions/arl-mode.el

@@ -0,0 +1,37 @@
+;;; arl-mode.el --- ARL mode for Emacs               -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2026  Aryadev Chavali
+
+;; Author: Aryadev Chavali <aryadev@aryadevchavali.com>
+;; Keywords:
+
+;; Copyright (C) 2026 Aryadev Chavali
+
+;; This program is distributed in the hope that it will be useful, but WITHOUT
+;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+;; FOR A PARTICULAR PURPOSE.  See the MIT License for details.
+
+;; You may distribute and modify this code under the terms of the MIT License,
+;; which you should have received a copy of along with this program.  If not,
+;; please go to <https://opensource.org/license/MIT>.
+
+;;; Commentary:
+
+;;
+
+;;; Code:
+
+(defvar arl-mode-comments '(?\; ";;" ("#|" . "|#")))
+(defvar arl-mode-keywords '("if" "then" "else"))
+(defvar arl-mode-expressions '(("\".*\"" . font-lock-string-face)))
+(defvar arl-mode-automode-list '("\\.arl"))
+
+(define-derived-mode arl-mode
+  arl-mode-comments
+  arl-mode-keywords
+  arl-mode-expressions
+  arl-mode-automode-list
+  nil)
+
+(provide 'arl-mode)
+;;; arl-mode.el ends here

include/arl/cli.h

@@ -0,0 +1,31 @@
+/* cli.h: CLI helpers
+ * Created: 2026-01-29
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef CLI_H
+#define CLI_H
+
+#include <stdio.h>
+
+#include <arl/lib/sv.h>
+
+int read_file(const char *filename, sv_t *ret);
+int read_pipe(FILE *pipe, sv_t *ret);
+void usage(FILE *fp);
+
+#endif
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
+
+ * You may distribute and modify this code under the terms of the MIT License,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://opensource.org/license/MIT>.
+
+ */

include/arl/lexer/lexer.h

@@ -1,38 +1,38 @@
-/* parser.h: Parser which takes character buffers and yields an AST
+/* lexer.h: Lexer which takes character buffers and yields a sequence of tokens.
  * Created: 2026-01-22
  * Author: Aryadev Chavali
  * License: See end of file
  * Commentary:
  */
 
-#ifndef PARSER_H
-#define PARSER_H
+#ifndef LEXER_H
+#define LEXER_H
 
-#include <arl/parser/ast.h>
+#include <arl/lexer/token.h>
 
-/// Parser streams, utilised when generating an AST.
+/// Token streams, utilised when lexing.
 typedef struct
 {
   u64 byte;
   sv_t contents;
-} parse_stream_t;
+} lex_stream_t;
 
-/// Types of errors that may occur during parsing
+/// Types of errors that may occur during lexing
 typedef enum
 {
-  PARSE_ERR_OK = 0,
-  PARSE_ERR_EXPECTED_SPEECH_MARKS,
-  PARSE_ERR_UNKNOWN_CHAR,
-} parse_err_t;
-const char *parse_err_to_string(parse_err_t err);
+  LEX_ERR_OK = 0,
+  LEX_ERR_EXPECTED_SPEECH_MARKS,
+  LEX_ERR_UNKNOWN_CHAR,
+} lex_err_t;
+const char *lex_err_to_string(lex_err_t err);
 
-// Generates an AST from STREAM, storing it in OUT.  Returns any errors it may
-// generate.
-parse_err_t parse(ast_t *out, parse_stream_t *stream);
+// Generates a token stream from a lex_stream_t, storing it in OUT.  Returns any
+// errors it may generate.
+lex_err_t lex_stream(token_stream_t *out, lex_stream_t *stream);
 
 // Computes the line and column that STREAM is currently pointing at in its
 // buffer, storing it in LINE and COL.
-void parse_stream_get_line_col(parse_stream_t *stream, u64 *line, u64 *col);
+void lex_stream_get_line_col(lex_stream_t *stream, u64 *line, u64 *col);
 
 #endif
 

include/arl/lexer/token.h

@@ -0,0 +1,73 @@
+/* token.h: General definition of tokens, and a sequence of them.
+ * Created: 2026-01-22
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef TOKEN_H
+#define TOKEN_H
+
+#include <arl/lib/base.h>
+#include <arl/lib/sv.h>
+#include <arl/lib/vec.h>
+
+/// Types of tokens
+typedef enum
+{
+  TOKEN_TYPE_KNOWN = 0,
+  TOKEN_TYPE_SYMBOL,
+  TOKEN_TYPE_STRING,
+
+  NUM_TOKEN_TYPES,
+} token_type_t;
+
+/// Known symbols which later stages would benefit from.
+typedef enum
+{
+  TOKEN_KNOWN_PUTS,
+  NUM_TOKEN_KNOWNS,
+} token_known_t;
+
+const char *token_known_to_cstr(token_known_t);
+
+/// Tokens are a tagged union
+typedef struct
+{
+  u64 byte_location;
+  token_type_t type;
+  union
+  {
+    token_known_t as_known;
+    sv_t as_symbol;
+    sv_t as_string;
+  };
+} token_t;
+
+token_t token_known(u64 byte, token_known_t known);
+token_t token_symbol(u64 byte, sv_t symbol);
+token_t token_string(u64 byte, sv_t string);
+void token_print(FILE *fp, token_t *token);
+
+/// Sequence of tokens
+typedef struct
+{
+  vec_t vec;
+} token_stream_t;
+
+void token_stream_free(token_stream_t *token);
+void token_stream_print(FILE *fp, token_stream_t *token);
+
+#endif
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
+
+ * You may distribute and modify this code under the terms of the MIT License,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://opensource.org/license/MIT>.
+
+ */

include/arl/lib/base.h

@@ -33,11 +33,32 @@ typedef double f64;
 #define MIN(A, B)  ((A) > (B) ? (B) : (A))
 #define ARRSIZE(A) ((sizeof(A)) / sizeof((A)[0]))
 
+#ifndef VERBOSE_LOGS
+#define VERBOSE_LOGS 0
+#endif
+
+#if VERBOSE_LOGS
+#define LOG(...)                  \
+  do                              \
+  {                               \
+    fprintf(stdout, "LOG: ");     \
+    fprintf(stdout, __VA_ARGS__); \
+  } while (0);
+#else
+#define LOG(...)
+#endif
+
+#define LOG_ERR(...)              \
+  do                              \
+  {                               \
+    fprintf(stderr, __VA_ARGS__); \
+  } while (0);
+
 #define FAIL(...)         \
   do                      \
   {                       \
-    fprintf(stderr, "FAIL: ");    \
-    fprintf(stderr, __VA_ARGS__); \
+    LOG_ERR("FAIL: ");    \
+    LOG_ERR(__VA_ARGS__); \
     assert(0);            \
   } while (0)
 

include/arl/lib/vec.h

@@ -31,9 +31,13 @@ typedef struct
 
 static_assert(sizeof(vec_t) == 64, "Expected sizeof(vec_t) to be 64");
 
+// standard old appending methods
 void vec_append(vec_t *vec, const void *const ptr, u64 size);
 void vec_append_byte(vec_t *vec, u8 byte);
 
+// vector-as-a-stack
+u8 *vec_pop(vec_t *vec, u64 size);
+
 // Returns pointer to the start of the buffer VEC is currently using to store
 // data (either its inline buffer or the heap buffer).
 void *vec_data(vec_t *vec);
@@ -43,8 +47,13 @@ void vec_ensure_capacity(vec_t *vec, u64 capacity);
 
 // Ensure VEC has at least SIZE bytes free
 void vec_ensure_free(vec_t *vec, u64 size);
+
+// Free the memory associated with the vector
 void vec_free(vec_t *vec);
 
+// Reset a vector while preserving any allocations
+void vec_reset(vec_t *vec);
+
 // Copy all data from V1 into V2.
 void vec_clone(vec_t *v2, vec_t *v1);
 

src/arl/main.c

@@ -1,82 +0,0 @@
-/* main.cpp:
- * Created: 2026-01-22
- * Author: Aryadev Chavali
- * License: See end of file
- * Commentary:
- */
-
-#include <assert.h>
-#include <ctype.h>
-#include <stdbool.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include <arl/lib/base.h>
-#include <arl/lib/sv.h>
-#include <arl/lib/vec.h>
-#include <arl/parser/ast.h>
-#include <arl/parser/parser.h>
-
-/// Parser
-sv_t read_file(const char *filename)
-{
-  FILE *fp = fopen(filename, "rb");
-  if (!fp)
-    FAIL("File `%s` does not exist\n", filename);
-
-  fseek(fp, 0, SEEK_END);
-  long size = ftell(fp);
-  fseek(fp, 0, SEEK_SET);
-  char *buffer = calloc(1, size + 1);
-  fread(buffer, size, 1, fp);
-  fclose(fp);
-
-  buffer[size] = '\0';
-  return SV(buffer, size);
-}
-
-int main(void)
-{
-  const char *filename = "./examples/hello-world.arl";
-  sv_t contents        = read_file(filename);
-  printf("%s\n=> `" PR_SV "`\n", filename, SV_FMT(contents));
-
-  parse_stream_t stream = {.byte = 0, .contents = contents};
-  ast_t ast             = {0};
-  parse_err_t perr      = parse(&ast, &stream);
-  if (perr)
-  {
-    u64 line = 1, col = 0;
-    parse_stream_get_line_col(&stream, &line, &col);
-
-    fprintf(stderr, "%s:%lu:%lu: %s\n", filename, line, col,
-            parse_err_to_string(perr));
-    goto fail;
-  }
-  printf("=> Parsed %lu objects\n", ast.objects.size / sizeof(obj_t));
-  ast_print(stdout, &ast);
-  printf("\n");
-
-  free(contents.data);
-  ast_free(&ast);
-  return 0;
-fail:
-  if (contents.data)
-    free(contents.data);
-  if (ast.objects.capacity > 0)
-    ast_free(&ast);
-  return 1;
-}
-
-/* Copyright (C) 2026 Aryadev Chavali
-
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
-
- * You may distribute and modify this code under the terms of the MIT License,
- * which you should have received a copy of along with this program.  If not,
- * please go to <https://opensource.org/license/MIT>.
-
- */

src/arl/parser/ast.c

@@ -1,88 +0,0 @@
-/* ast.c: Implementation of AST constructor/destructor functions
- * Created: 2026-01-22
- * Author: Aryadev Chavali
- * License: See end of file
- * Commentary: See ast.h.
- */
-
-#include <arl/lib/vec.h>
-#include <arl/parser/ast.h>
-
-obj_t obj_string(u64 byte, sv_t string)
-{
-  return (obj_t){
-      .byte  = byte,
-      .type  = TYPE_STRING,
-      .value = {string},
-  };
-}
-
-obj_t obj_symbol(u64 byte, sv_t symbol)
-{
-  return (obj_t){
-      .byte  = byte,
-      .type  = TYPE_SYMBOL,
-      .value = {symbol},
-  };
-}
-
-void obj_print(FILE *fp, obj_t *obj)
-{
-  if (!obj)
-  {
-    fprintf(fp, "NIL");
-    return;
-  }
-  switch (obj->type)
-  {
-  case TYPE_SYMBOL:
-    fprintf(fp, "SYMBOL(" PR_SV ")", SV_FMT(obj->value.as_symbol));
-    break;
-  case TYPE_STRING:
-    fprintf(fp, "STRING(" PR_SV ")", SV_FMT(obj->value.as_string));
-    break;
-  }
-}
-
-void ast_print(FILE *fp, ast_t *ast)
-{
-  if (!ast)
-  {
-    fprintf(fp, "{}");
-    return;
-  }
-  fprintf(fp, "{");
-  if (ast->objects.size == 0)
-  {
-    fprintf(fp, "}\n");
-    return;
-  }
-
-  fprintf(fp, "\n");
-  for (u64 i = 0; i < ast->objects.size / sizeof(obj_t); ++i)
-  {
-    obj_t item = VEC_GET(&ast->objects, i, obj_t);
-    fprintf(fp, "\t[%lu]: ", i);
-    obj_print(fp, &item);
-    fprintf(fp, "\n");
-  }
-  fprintf(fp, "}");
-}
-
-void ast_free(ast_t *ast)
-{
-  // we can free the vector itself and we're done
-  vec_free(&ast->objects);
-}
-
-/* Copyright (C) 2026 Aryadev Chavali
-
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
-
- * You may distribute and modify this code under the terms of the MIT License,
- * which you should have received a copy of along with this program.  If not,
- * please go to <https://opensource.org/license/MIT>.
-
- */

src/arl/parser/ast.h

@@ -1,61 +0,0 @@
-/* ast.h: General definition of the AST and objects within it.
- * Created: 2026-01-22
- * Author: Aryadev Chavali
- * License: See end of file
- * Commentary:
- */
-
-#ifndef AST_H
-#define AST_H
-
-#include <arl/lib/base.h>
-#include <arl/lib/sv.h>
-#include <arl/lib/vec.h>
-
-/// Types the AST can encode
-typedef enum
-{
-  TYPE_SYMBOL,
-  TYPE_STRING,
-} type_t;
-
-/// Node of the AST as a tagged union
-typedef struct
-{
-  u64 byte;
-  type_t type;
-  union
-  {
-    sv_t as_string;
-    sv_t as_symbol;
-  } value;
-} obj_t;
-
-// Constructors
-obj_t obj_string(u64 byte, sv_t string);
-obj_t obj_symbol(u64 byte, sv_t symbol);
-
-void obj_print(FILE *fp, obj_t *obj);
-
-/// The AST as a flat collection of nodes
-typedef struct
-{
-  vec_t objects;
-} ast_t;
-
-void ast_free(ast_t *ast);
-void ast_print(FILE *fp, ast_t *ast);
-
-#endif
-
-/* Copyright (C) 2026 Aryadev Chavali
-
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
-
- * You may distribute and modify this code under the terms of the MIT License,
- * which you should have received a copy of along with this program.  If not,
- * please go to <https://opensource.org/license/MIT>.
-
- */

src/arl/parser/parser.c

@@ -1,164 +0,0 @@
-/* parser.c: Implementation of parser.
- * Created: 2026-01-22
- * Author: Aryadev Chavali
- * License: See end of file
- * Commentary: See parser.h
- */
-
-#include "arl/lib/sv.h"
-#include <ctype.h>
-#include <string.h>
-
-#include <arl/parser/parser.h>
-
-/// Expected characters in a symbol
-static const char *SYMBOL_CHARS =
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&'()*+,-./"
-    ":;<=>?@\\^_`{|}~0123456789";
-
-const char *parse_err_to_string(parse_err_t err)
-{
-  switch (err)
-  {
-  case PARSE_ERR_OK:
-    return "OK";
-  case PARSE_ERR_EXPECTED_SPEECH_MARKS:
-    return "EXPECTED_SPEECH_MARKS";
-  case PARSE_ERR_UNKNOWN_CHAR:
-    return "UNKNOWN_CHAR";
-  default:
-    FAIL("Unexpected value for parse_err_t: %d\n", err);
-  }
-}
-
-/// Prototypes for streams
-bool stream_eos(parse_stream_t *stream);
-char stream_peek(parse_stream_t *stream);
-void stream_advance(parse_stream_t *stream, u64 size);
-u64 stream_size(parse_stream_t *stream);
-
-void parse_stream_get_line_col(parse_stream_t *stream, u64 *line, u64 *col)
-{
-  assert(stream && line && col && "Expected valid pointers.");
-  for (u64 i = 0; i < stream->byte; ++i)
-  {
-    char c = stream->contents.data[i];
-    if (c == '\n')
-    {
-      *line += 1;
-      *col = 0;
-    }
-    else
-    {
-      *col += 1;
-    }
-  }
-}
-
-/// Prototypes for parsing subroutines
-parse_err_t parse_string(parse_stream_t *stream, obj_t *ret);
-parse_err_t parse_symbol(parse_stream_t *stream, obj_t *ret);
-
-parse_err_t parse(ast_t *out, parse_stream_t *stream)
-{
-  assert(out && stream && "Expected valid pointers");
-  while (!stream_eos(stream))
-  {
-    char cur = stream_peek(stream);
-    if (isspace(cur))
-    {
-      while (isspace(cur) && !stream_eos(stream))
-      {
-        stream_advance(stream, 1);
-        cur = stream_peek(stream);
-      }
-    }
-    else if (cur == '"')
-    {
-      // we make a copy for parse_string to mess with
-      obj_t ret        = {0};
-      parse_err_t perr = parse_string(stream, &ret);
-      if (perr)
-        return perr;
-      vec_append(&out->objects, &ret, sizeof(ret));
-    }
-    else if (strchr(SYMBOL_CHARS, cur) && !isdigit(cur))
-    {
-      // we make a copy for parse_symbol to mess with
-      obj_t ret        = {0};
-      parse_err_t perr = parse_symbol(stream, &ret);
-      if (perr)
-        return perr;
-
-      vec_append(&out->objects, &ret, sizeof(ret));
-    }
-    else
-    {
-      return PARSE_ERR_UNKNOWN_CHAR;
-    }
-  }
-  return PARSE_ERR_OK;
-}
-
-parse_err_t parse_string(parse_stream_t *stream, obj_t *ret)
-{
-  // Increment the cursor just past the first speechmark
-  stream_advance(stream, 1);
-  sv_t current_contents = sv_chop_left(stream->contents, stream->byte);
-  u64 string_size       = sv_till(current_contents, "\"");
-  if (string_size + stream->byte == stream_size(stream))
-    return PARSE_ERR_EXPECTED_SPEECH_MARKS;
-  // Bounds of string are well defined, generate an object and advance the
-  // stream
-  *ret = obj_string(stream->byte - 1, SV(current_contents.data, string_size));
-  stream_advance(stream, string_size + 1);
-  return PARSE_ERR_OK;
-}
-
-parse_err_t parse_symbol(parse_stream_t *stream, obj_t *ret)
-{
-  sv_t current_contents = sv_chop_left(stream->contents, stream->byte);
-  u64 symbol_size       = sv_while(current_contents, SYMBOL_CHARS);
-  // Generate symbol
-  *ret = obj_symbol(stream->byte, SV(current_contents.data, symbol_size));
-  stream_advance(stream, symbol_size);
-  return PARSE_ERR_OK;
-}
-
-bool stream_eos(parse_stream_t *stream)
-{
-  return stream->byte >= stream->contents.size;
-}
-
-char stream_peek(parse_stream_t *stream)
-{
-  if (stream_eos(stream))
-    return '\0';
-  else
-    return stream->contents.data[stream->byte];
-}
-
-void stream_advance(parse_stream_t *stream, u64 size)
-{
-  if (stream->byte + size >= stream->contents.size)
-    stream->byte = stream->contents.size;
-  else
-    stream->byte += size;
-}
-
-u64 stream_size(parse_stream_t *stream)
-{
-  return stream->contents.size;
-}
-
-/* Copyright (C) 2026 Aryadev Chavali
-
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
-
- * You may distribute and modify this code under the terms of the MIT License,
- * which you should have received a copy of along with this program.  If not,
- * please go to <https://opensource.org/license/MIT>.
-
- */

src/cli.c

@@ -0,0 +1,83 @@
+/* cli.c:
+ * Created: 2026-01-29
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary: See /include/arl/cli.h
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <arl/cli.h>
+#include <arl/lib/vec.h>
+
+int read_file(const char *filename, sv_t *ret)
+{
+  // NOTE: Stupidly simple.  Presumes the file is NOT three pipes in a trench
+  // coat.
+  FILE *fp = fopen(filename, "rb");
+  if (!fp)
+    return 1;
+
+  fseek(fp, 0, SEEK_END);
+  ret->size = ftell(fp);
+  fseek(fp, 0, SEEK_SET);
+  ret->data = calloc(1, ret->size + 1);
+  fread(ret->data, ret->size, 1, fp);
+  fclose(fp);
+
+  ret->data[ret->size] = '\0';
+  return 0;
+}
+
+int read_pipe(FILE *pipe, sv_t *ret)
+{
+  // NOTE: We can't read an entire pipe at once like we did for read_file.  So
+  // let's read in buffered chunks, with a vector to keep them contiguous.
+  vec_t contents = {0};
+  char buffer[1024];
+  while (!feof(pipe))
+  {
+    size_t bytes_read = fread(buffer, 1, sizeof(buffer), pipe);
+    vec_append(&contents, buffer, bytes_read);
+  }
+
+  ret->size = contents.size;
+  // Get that null terminator in, but only after we've recorded the actual size
+  // of what's been read.
+  vec_append_byte(&contents, '\0');
+
+  if (contents.not_inlined)
+  {
+    // Take the heap pointer from us.
+    ret->data = vec_data(&contents);
+  }
+  else
+  {
+    // vec_data(&contents) is stack allocated; can't carry that out of this
+    // function!
+    ret->data = calloc(1, contents.size);
+    memcpy(ret->data, vec_data(&contents), contents.size);
+  }
+  return 0;
+}
+
+void usage(FILE *fp)
+{
+  fprintf(fp, "Usage: arl [FILE]\n"
+              "Compiles [FILE] as ARL source code.\n"
+              "  [FILE]: File to compile.\n"
+              "If FILE is \"--\", then read from stdin.\n");
+}
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
+
+ * You may distribute and modify this code under the terms of the MIT License,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://opensource.org/license/MIT>.
+
+ */

src/lexer/lexer.c

@@ -0,0 +1,184 @@
+/* lexr.c: Implementation of lexr.
+ * Created: 2026-01-22
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary: See /include/arl/lexer/lexer.h
+ */
+
+#include <ctype.h>
+#include <string.h>
+
+#include <arl/lexer/lexer.h>
+#include <arl/lexer/token.h>
+#include <arl/lib/sv.h>
+
+/// Expected characters in a symbol
+static const char *SYMBOL_CHARS =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&'()*+,-./"
+    ":;<=>?@\\^_`{|}~0123456789";
+
+const char *lex_err_to_string(lex_err_t err)
+{
+  switch (err)
+  {
+  case LEX_ERR_OK:
+    return "OK";
+  case LEX_ERR_EXPECTED_SPEECH_MARKS:
+    return "EXPECTED_SPEECH_MARKS";
+  case LEX_ERR_UNKNOWN_CHAR:
+    return "UNKNOWN_CHAR";
+  default:
+    FAIL("Unexpected lex_err_t value: %d\n", err);
+  }
+}
+
+/// Prototypes for streams
+bool stream_eos(lex_stream_t *stream);
+char stream_peek(lex_stream_t *stream);
+void stream_advance(lex_stream_t *stream, u64 size);
+u64 stream_size(lex_stream_t *stream);
+
+void lex_stream_get_line_col(lex_stream_t *stream, u64 *line, u64 *col)
+{
+  assert(stream && line && col && "Expected valid pointers.");
+  for (u64 i = 0; i < stream->byte; ++i)
+  {
+    char c = stream->contents.data[i];
+    if (c == '\n')
+    {
+      *line += 1;
+      *col = 0;
+    }
+    else
+    {
+      *col += 1;
+    }
+  }
+}
+
+/// Prototypes for lexing subroutines
+lex_err_t lex_string(lex_stream_t *stream, token_t *ret);
+lex_err_t lex_symbol(lex_stream_t *stream, token_t *ret);
+
+lex_err_t lex_stream(token_stream_t *out, lex_stream_t *stream)
+{
+  assert(out && stream && "Expected valid pointers");
+  while (!stream_eos(stream))
+  {
+    char cur = stream_peek(stream);
+    if (isspace(cur))
+    {
+      while (isspace(cur) && !stream_eos(stream))
+      {
+        stream_advance(stream, 1);
+        cur = stream_peek(stream);
+      }
+    }
+    else if (cur == '"')
+    {
+      // we make a copy for lex_string to mess with
+      token_t ret    = {0};
+      lex_err_t perr = lex_string(stream, &ret);
+      if (perr)
+        return perr;
+      vec_append(&out->vec, &ret, sizeof(ret));
+    }
+    else if (strchr(SYMBOL_CHARS, cur) && !isdigit(cur))
+    {
+      // we make a copy for lex_symbol to mess with
+      token_t ret    = {0};
+      lex_err_t perr = lex_symbol(stream, &ret);
+      if (perr)
+        return perr;
+
+      vec_append(&out->vec, &ret, sizeof(ret));
+    }
+    else
+    {
+      return LEX_ERR_UNKNOWN_CHAR;
+    }
+  }
+  return LEX_ERR_OK;
+}
+
+lex_err_t lex_string(lex_stream_t *stream, token_t *ret)
+{
+  // Increment the cursor just past the first speechmark
+  stream_advance(stream, 1);
+  sv_t string = sv_chop_left(stream->contents, stream->byte);
+  string.size = sv_till(string, "\"");
+
+  // If we're at the edge of the stream, there must not have been any
+  // speechmarks.
+  if (string.size + stream->byte == stream_size(stream))
+    return LEX_ERR_EXPECTED_SPEECH_MARKS;
+
+  // `string` is well defined, package and throw it back.
+  *ret = token_string(stream->byte - 1, string);
+  stream_advance(stream, string.size + 1);
+  return LEX_ERR_OK;
+}
+
+lex_err_t lex_symbol(lex_stream_t *stream, token_t *ret)
+{
+  sv_t symbol = sv_chop_left(stream->contents, stream->byte);
+  symbol.size = sv_while(symbol, SYMBOL_CHARS);
+
+  // see if symbol is one of the already known symbols
+  static_assert(NUM_TOKEN_KNOWNS == 1, "Expected number of TOKEN_KNOWNs");
+  for (token_known_t i = 0; i < NUM_TOKEN_KNOWNS; ++i)
+  {
+    const char *possible_known = token_known_to_cstr(i);
+    if (strlen(possible_known) == symbol.size &&
+        strncmp(possible_known, symbol.data, symbol.size) == 0)
+    {
+      // Found a matching known symbol
+      *ret = token_known(stream->byte, i);
+      goto end;
+    }
+  }
+
+  // otherwise, it must be a fresh symbol i.e. user defined
+  *ret = token_symbol(stream->byte, symbol);
+end:
+  stream_advance(stream, symbol.size);
+  return LEX_ERR_OK;
+}
+
+bool stream_eos(lex_stream_t *stream)
+{
+  return stream->byte >= stream->contents.size;
+}
+
+char stream_peek(lex_stream_t *stream)
+{
+  if (stream_eos(stream))
+    return '\0';
+  else
+    return stream->contents.data[stream->byte];
+}
+
+void stream_advance(lex_stream_t *stream, u64 size)
+{
+  if (stream->byte + size >= stream->contents.size)
+    stream->byte = stream->contents.size;
+  else
+    stream->byte += size;
+}
+
+u64 stream_size(lex_stream_t *stream)
+{
+  return stream->contents.size;
+}
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
+
+ * You may distribute and modify this code under the terms of the MIT License,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://opensource.org/license/MIT>.
+
+ */

src/lexer/token.c

@@ -0,0 +1,115 @@
+/* token.c: Implementation of TOKEN constructor/destructor functions
+ * Created: 2026-01-22
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary: See /include/arl/lexer/token.h.
+ */
+
+#include <arl/lexer/token.h>
+#include <arl/lib/base.h>
+#include <arl/lib/vec.h>
+
+const char *token_known_to_cstr(token_known_t known)
+{
+  switch (known)
+  {
+  case TOKEN_KNOWN_PUTS:
+    return "puts";
+  default:
+    FAIL("Unexpected TOKEN_KNOWN value: %d\n", known);
+  }
+}
+
+token_t token_known(u64 byte, token_known_t known)
+{
+  return (token_t){
+      .byte_location = byte,
+      .type          = TOKEN_TYPE_KNOWN,
+      .as_known      = known,
+  };
+}
+
+token_t token_string(u64 byte, sv_t string)
+{
+  return (token_t){
+      .byte_location = byte,
+      .type          = TOKEN_TYPE_STRING,
+      .as_string     = string,
+  };
+}
+
+token_t token_symbol(u64 byte, sv_t symbol)
+{
+  return (token_t){
+      .byte_location = byte,
+      .type          = TOKEN_TYPE_SYMBOL,
+      .as_symbol     = symbol,
+  };
+}
+
+void token_print(FILE *fp, token_t *token)
+{
+  if (!token)
+  {
+    fprintf(fp, "NIL");
+    return;
+  }
+  switch (token->type)
+  {
+  case TOKEN_TYPE_KNOWN:
+    fprintf(fp, "KNOWN(%s)", token_known_to_cstr(token->as_known));
+    break;
+  case TOKEN_TYPE_SYMBOL:
+    fprintf(fp, "SYMBOL(" PR_SV ")", SV_FMT(token->as_symbol));
+    break;
+  case TOKEN_TYPE_STRING:
+    fprintf(fp, "STRING(" PR_SV ")", SV_FMT(token->as_string));
+    break;
+  case NUM_TOKEN_TYPES:
+  default:
+    FAIL("Unexpected token type: %d\n", token->type);
+  }
+}
+
+void token_stream_print(FILE *fp, token_stream_t *token)
+{
+  if (!token)
+  {
+    fprintf(fp, "{}");
+    return;
+  }
+  fprintf(fp, "{");
+  if (token->vec.size == 0)
+  {
+    fprintf(fp, "}\n");
+    return;
+  }
+
+  fprintf(fp, "\n");
+  for (u64 i = 0; i < token->vec.size / sizeof(token_t); ++i)
+  {
+    token_t item = VEC_GET(&token->vec, i, token_t);
+    fprintf(fp, "\t[%lu]: ", i);
+    token_print(fp, &item);
+    fprintf(fp, "\n");
+  }
+  fprintf(fp, "}");
+}
+
+void token_stream_free(token_stream_t *stream)
+{
+  // we can free the vector itself and we're done
+  vec_free(&stream->vec);
+}
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
+
+ * You may distribute and modify this code under the terms of the MIT License,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://opensource.org/license/MIT>.
+
+ */

src/lib/sv.c

@@ -2,7 +2,7 @@
  * Created: 2026-01-22
  * Author: Aryadev Chavali
  * License: See end of file
- * Commentary: See /include/sv.h
+ * Commentary: See /include/arl/lib/sv.h
  */
 
 #include <string.h>

src/lib/vec.c

@@ -2,7 +2,7 @@
  * Created: 2026-01-22
  * Author: Aryadev Chavali
  * License: See end of file
- * Commentary:
+ * Commentary: See /include/arl/lib/vec.h
 
  Taken from prick_vec.h: see https://github.com/oreodave/prick.
  */
@@ -31,6 +31,14 @@ void vec_append_byte(vec_t *vec, u8 byte)
   ++vec->size;
 }
 
+u8 *vec_pop(vec_t *vec, u64 size)
+{
+  if (!vec || vec->size < size)
+    return NULL;
+  vec->size -= size;
+  return (u8 *)vec_data(vec) + vec->size;
+}
+
 void *vec_data(vec_t *vec)
 {
   if (!vec)
@@ -89,6 +97,14 @@ void vec_free(vec_t *vec)
   memset(vec, 1, sizeof(*vec));
 }
 
+void vec_reset(vec_t *vec)
+{
+  if (!vec)
+    return;
+  memset(vec_data(vec), 0, vec->capacity);
+  vec->size = 0;
+}
+
 void vec_clone(vec_t *v2, vec_t *v1)
 {
   if (!v1 || !v2)

src/main.c

@@ -0,0 +1,96 @@
+/* main.c:
+ * Created: 2026-01-22
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#include <assert.h>
+#include <ctype.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <arl/lexer/lexer.h>
+#include <arl/lexer/token.h>
+#include <arl/lib/base.h>
+#include <arl/lib/sv.h>
+#include <arl/lib/vec.h>
+
+#include <arl/cli.h>
+
+int main(int argc, char *argv[])
+{
+  int ret        = 0;
+  char *filename = "";
+  if (argc == 1)
+  {
+    usage(stderr);
+    ret = 1;
+    goto end;
+  }
+  else
+  {
+    filename = argv[1];
+  }
+
+  int read_err  = 0;
+  sv_t contents = {0};
+  if (strcmp(filename, "--") == 0)
+  {
+    filename = "stdin";
+    read_err = read_pipe(stdin, &contents);
+  }
+  else
+  {
+    read_err = read_file(filename, &contents);
+  }
+
+  if (read_err)
+  {
+    LOG_ERR("ERROR: Reading `%s`: ", filename);
+    perror("");
+    ret = 1;
+    goto end;
+  }
+
+  LOG("%s => `" PR_SV "`\n", filename, SV_FMT(contents));
+
+  lex_stream_t stream   = {.byte = 0, .contents = contents};
+  token_stream_t tokens = {0};
+  lex_err_t perr        = lex_stream(&tokens, &stream);
+  if (perr)
+  {
+    u64 line = 1, col = 0;
+    lex_stream_get_line_col(&stream, &line, &col);
+
+    LOG_ERR("%s:%lu:%lu: %s\n", filename, line, col, lex_err_to_string(perr));
+    ret = 1;
+    goto end;
+  }
+
+#if VERBOSE_LOGS
+  LOG("Lexed %lu tokens ", tokens.vec.size / sizeof(token_t));
+  token_stream_print(stdout, &tokens);
+  printf("\n");
+#endif
+
+end:
+  if (contents.data)
+    free(contents.data);
+  token_stream_free(&tokens);
+  return ret;
+}
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the MIT License for details.
+
+ * You may distribute and modify this code under the terms of the MIT License,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://opensource.org/license/MIT>.
+
+ */