add parser

Makefile

@@ -8,10 +8,12 @@ C_FLAGS = \
 	-Wextra \
 	-Wpedantic \
 	-Wconversion \
-	-Wno-gnu-case-range
+	-Wno-gnu-case-range \
+	-g
 
 LINKER_FLAGS = \
-	-fsanitize=address,undefined
+	-fsanitize=address,undefined \
+	-g
 
 SOURCE_FOLDER = src
 BUILD_FOLDER = build

src/lexer.c

@@ -1 +1,532 @@
 #include "lexer.h"
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+bool string_slice_equal(StringSlice slice, const char* data)
+{
+    if (strlen(data) != slice.length) {
+        return false;
+    }
+    return strncmp(data, slice.data, slice.length) == 0;
+}
+
+void string_construct(String* string)
+{
+    *string = (String) {
+        .data = NULL,
+        .length = 0,
+        .capacity = 0,
+    };
+}
+
+void string_destroy(String* string)
+{
+    if (string->data) {
+        free(string->data);
+    }
+}
+
+const size_t string_starting_alloc_size = 8;
+
+void string_append_char(String* string, char value)
+{
+    if (string->length + 1 >= string->capacity) {
+        if (string->capacity == 0) {
+            string->capacity = string_starting_alloc_size;
+        } else {
+            string->capacity *= 2;
+        }
+        if (string->data == NULL) {
+            string->data = malloc(string->capacity * sizeof(char));
+            ASSERT(string->data);
+        } else {
+            char* new_buffer
+                = realloc(string->data, string->capacity * sizeof(char));
+            ASSERT(new_buffer);
+            string->data = new_buffer;
+        }
+    }
+    string->data[string->length] = value;
+    string->length += 1;
+}
+
+void string_from_cstr(String* string, const char* value)
+{
+    string_construct(string);
+    string_append_cstr(string, value);
+}
+
+void string_from_slice(String* string, StringSlice slice)
+{
+    string_construct(string);
+    for (size_t i = 0; i < slice.length; ++i) {
+        string_append_char(string, slice.data[i]);
+    }
+}
+
+void file_char_reader_construct(FileCharReader* reader, FILE* file)
+{
+    *reader = (FileCharReader) {
+        .next = file_char_reader_next,
+        .value = file_char_reader_value,
+        .file = file,
+        .buffer = { 0 },
+    };
+    string_construct(&reader->buffer);
+}
+
+void string_append_cstr(String* string, const char* value)
+{
+    size_t value_length = strlen(value);
+
+    if (string->length + value_length + 1 > string->capacity) {
+        if (string->capacity == 0) {
+            string->capacity = string_starting_alloc_size;
+        } else {
+            string->capacity *= 2;
+        }
+        while (string->length + value_length + 1 > string->capacity) {
+            string->capacity *= 2;
+        }
+        char* new_buffer
+            = realloc(string->data, string->capacity * sizeof(char));
+        ASSERT(new_buffer);
+        string->data = new_buffer;
+    }
+
+    strncpy(&string->data[string->length], value, value_length);
+}
+
+void string_append_formatted(String* string, const char* format, ...)
+{
+    va_list varargs;
+    va_start(varargs, format);
+
+    size_t format_length = (size_t)vsnprintf(NULL, 0, format, varargs);
+
+    if (string->length + format_length + 1 > string->capacity) {
+        if (string->capacity == 0) {
+            string->capacity = string_starting_alloc_size;
+        } else {
+            string->capacity *= 2;
+        }
+        while (string->length + format_length + 1 > string->capacity) {
+            string->capacity *= 2;
+        }
+        char* new_buffer
+            = realloc(string->data, string->capacity * sizeof(char));
+        ASSERT(new_buffer);
+        string->data = new_buffer;
+    }
+
+    size_t written = (size_t)vsnprintf(
+        &string->data[string->length],
+        string->capacity - string->length,
+        format,
+        varargs
+    );
+    ASSERT(written == format_length);
+    string->length += written;
+
+    va_end(varargs);
+}
+
+bool string_equal(const String* string, const char* value)
+{
+    return strncmp(value, string->data, string->length + 1);
+}
+
+void file_char_reader_destroy(FileCharReader* reader)
+{
+    string_destroy(&reader->buffer);
+}
+
+char file_char_reader_next(FileCharReader* reader)
+{
+    int read_maybe_char = fgetc(reader->file);
+    if (read_maybe_char == EOF) {
+        return '\0';
+    }
+    char read_char = (char)read_maybe_char;
+    string_append_char(&reader->buffer, read_char);
+    return (char)read_char;
+}
+
+StringSlice file_char_reader_value(
+    const FileCharReader* reader, size_t index, size_t length
+)
+{
+    ASSERT(index + length <= reader->buffer.length);
+    return (StringSlice) {
+        .data = &reader->buffer.data[index],
+        .length = length,
+    };
+}
+
+void error_construct(Error* error, Pos pos, String message)
+{
+    *error = (Error) {
+        .pos = pos,
+        .message = message,
+    };
+}
+
+void error_destroy(Error* error) { string_destroy(&error->message); }
+
+void error_collector_construct(ErrorCollector* collector)
+{
+    const size_t errors_start_capacity = 64;
+    *collector = (ErrorCollector) {
+        .errors = malloc(errors_start_capacity * sizeof(Error)),
+        .errors_length = 0,
+        .errors_capacity = errors_start_capacity,
+    };
+}
+
+void error_collector_destroy(ErrorCollector* collector)
+{
+    for (size_t i = 0; i < collector->errors_length; ++i) {
+        error_destroy(&collector->errors[i]);
+    }
+    free(collector->errors);
+}
+
+void error_collector_add(ErrorCollector* collector, Error error)
+{
+    if (collector->errors_length >= collector->errors_capacity) {
+        Error* new_buffer = realloc(
+            collector->errors, collector->errors_capacity * sizeof(Error)
+        );
+        ASSERT(new_buffer);
+        collector->errors = new_buffer;
+    }
+    collector->errors[collector->errors_length] = error;
+    collector->errors_length += 1;
+}
+
+const char* token_type_value(TokenType type)
+{
+    switch (type) {
+        case TokenTypeEof:
+            return "Eof";
+        case TokenTypeError:
+            return "error";
+        case TokenTypeId:
+            return "Id";
+        case TokenTypeInt:
+            return "Int";
+        case TokenTypeChar:
+            return "Char";
+        case TokenTypeString:
+            return "String";
+        case TokenTypeLParen:
+            return "(";
+        case TokenTypeRParen:
+            return ")";
+        case TokenTypeLBrace:
+            return "{";
+        case TokenTypeRBrace:
+            return "}";
+        case TokenTypeLBracket:
+            return "[";
+        case TokenTypeRBracket:
+            return "]";
+    }
+}
+
+#define LEXER_ADD_ERROR(LEXER, POS, ...)                                       \
+    {                                                                          \
+        String error_message;                                                  \
+        string_construct(&error_message);                                      \
+        string_append_formatted(&error_message, __VA_ARGS__);                  \
+        Error error;                                                           \
+        error_construct(&error, (POS), error_message);                         \
+        error_collector_add((LEXER)->errors, error);                           \
+    }
+
+Lexer lexer_create(CharReader* reader, ErrorCollector* errors)
+{
+    return (Lexer) {
+        .reader = reader,
+        .errors = errors,
+        .current = reader->next(reader),
+        .pos = { 0, 1, 1 },
+    };
+}
+
+Token lexer_next(Lexer* lexer)
+{
+    Pos pos = lexer->pos;
+    if (lexer_done(lexer)) {
+        return lexer_token(lexer, TokenTypeEof, pos);
+    }
+    switch (lexer->current) {
+        case ' ':
+        case '\t':
+        case '\r':
+        case '\n':
+            return lexer_skip_whitespace(lexer);
+        case '"':
+            return lexer_lex_string(lexer);
+        case '(':
+            return (
+                lexer_step(lexer), lexer_token(lexer, TokenTypeLParen, pos)
+            );
+        case ')':
+            return (
+                lexer_step(lexer), lexer_token(lexer, TokenTypeRParen, pos)
+            );
+        case '{':
+            return (
+                lexer_step(lexer), lexer_token(lexer, TokenTypeLBrace, pos)
+            );
+        case '}':
+            return (
+                lexer_step(lexer), lexer_token(lexer, TokenTypeRBrace, pos)
+            );
+        case '[':
+            return (
+                lexer_step(lexer), lexer_token(lexer, TokenTypeLBracket, pos)
+            );
+        case ']':
+            return (
+                lexer_step(lexer), lexer_token(lexer, TokenTypeRBracket, pos)
+            );
+        case '/':
+            return lexer_lex_slash(lexer);
+        case '#':
+            return lexer_lex_hashtag(lexer);
+        case '0' ... '9':
+            return lexer_lex_int(lexer);
+        case '+':
+        case '-':
+        case '*':
+        case '<':
+        case '>':
+        case '=':
+        case '!':
+        case 'a' ... 'z':
+        case 'A' ... 'Z':
+            return lexer_lex_id(lexer);
+        default:
+            LEXER_ADD_ERROR(
+                lexer, pos, "unsupported character `%c`", lexer->current
+            );
+            return (lexer_step(lexer), lexer_token(lexer, TokenTypeError, pos));
+    }
+}
+
+Token lexer_lex_id(Lexer* lexer)
+{
+    Pos pos = lexer->pos;
+    lexer_step(lexer);
+    while (true) {
+        switch (lexer->current) {
+            case '+':
+            case '-':
+            case '*':
+            case '<':
+            case '>':
+            case '=':
+            case '!':
+            case '0' ... '9':
+            case 'a' ... 'z':
+            case 'A' ... 'Z':
+                lexer_step(lexer);
+                break;
+            default:
+                goto break_loop;
+        }
+    }
+break_loop:
+    return lexer_token(lexer, TokenTypeId, pos);
+}
+
+Token lexer_lex_int(Lexer* lexer)
+{
+    Pos pos = lexer->pos;
+    lexer_step(lexer);
+    while (true) {
+        switch (lexer->current) {
+            case '0' ... '9':
+                lexer_step(lexer);
+                break;
+            default:
+                goto break_loop;
+        }
+    }
+break_loop:
+    return lexer_token(lexer, TokenTypeInt, pos);
+}
+
+Token lexer_lex_char(Lexer* lexer)
+{
+    Pos pos = lexer->pos;
+    lexer_step(lexer);
+    if (lexer_done(lexer)) {
+        LEXER_ADD_ERROR(
+            lexer, pos, "malformed character literal, got unexpected Eof"
+        );
+        return lexer_token(lexer, TokenTypeError, pos);
+    }
+    if (lexer->current == '\'') {
+        LEXER_ADD_ERROR(
+            lexer, pos, "malformed character literal, got unexpected `'`"
+        );
+        return lexer_token(lexer, TokenTypeError, pos);
+    }
+    if (lexer->current == '\\') {
+        lexer_step(lexer);
+        if (lexer_done(lexer)) {
+            LEXER_ADD_ERROR(
+                lexer, pos, "malformed character literal, got unexpected Eof"
+            );
+            return lexer_token(lexer, TokenTypeError, pos);
+        }
+        lexer_step(lexer);
+    }
+    if (lexer_done(lexer)) {
+        LEXER_ADD_ERROR(
+            lexer, pos, "malformed character literal, expected `'`, got Eof"
+        );
+        return lexer_token(lexer, TokenTypeError, pos);
+    }
+    if (lexer->current != '\'') {
+        LEXER_ADD_ERROR(
+            lexer,
+            pos,
+            "malformed character literal, expected `'`, got `%c`",
+            lexer->current
+        );
+        return lexer_token(lexer, TokenTypeError, pos);
+    }
+    lexer_step(lexer);
+    return lexer_token(lexer, TokenTypeChar, pos);
+}
+
+Token lexer_lex_string(Lexer* lexer)
+{
+    Pos pos = lexer->pos;
+    lexer_step(lexer);
+    while (!lexer_done(lexer)) {
+        char maybe_escape_char = lexer->current;
+        lexer_step(lexer);
+        if (maybe_escape_char == '\\') {
+            if (lexer_done(lexer)) {
+                LEXER_ADD_ERROR(
+                    lexer,
+                    pos,
+                    "malformed string literal escape sequence, got unexpected "
+                    "Eof"
+                );
+                return lexer_token(lexer, TokenTypeError, pos);
+            }
+            lexer_step(lexer);
+        }
+    }
+    if (lexer_done(lexer)) {
+        LEXER_ADD_ERROR(
+            lexer, pos, "malformed string literal, expected `\"`, got Eof"
+        );
+        return lexer_token(lexer, TokenTypeError, pos);
+    }
+    if (lexer->current != '\"') {
+        LEXER_ADD_ERROR(
+            lexer,
+            pos,
+            "malformed string literal, expected `\"`, got `%c`",
+            lexer->current
+        );
+        return lexer_token(lexer, TokenTypeError, pos);
+    }
+    lexer_step(lexer);
+    return lexer_token(lexer, TokenTypeString, pos);
+}
+
+Token lexer_lex_slash(Lexer* lexer)
+{
+    Pos pos = lexer->pos;
+    lexer_step(lexer);
+    if (lexer->current == '*') {
+        lexer_step(lexer);
+        int depth = 1;
+        char last = '\0';
+        while (!lexer_done(lexer) && depth > 0) {
+            if (last == '*' && lexer->current == '/') {
+                depth -= 1;
+            } else if (last == '/' && lexer->current == '*') {
+                depth += 1;
+            }
+            last = lexer->current;
+            lexer_step(lexer);
+        }
+        if (depth > 0) {
+            String error_message;
+            string_from_cstr(
+                &error_message,
+                "malformed multiline comment, expected `*/` before end"
+            );
+            Error error;
+            error_construct(&error, pos, error_message);
+            error_collector_add(lexer->errors, error);
+            return lexer_token(lexer, TokenTypeError, pos);
+        }
+        return lexer_next(lexer);
+    }
+    if (lexer->current == '/') {
+        lexer_step(lexer);
+        while (!lexer_done(lexer) && lexer->current != '\n') {
+            lexer_step(lexer);
+        }
+        return lexer_next(lexer);
+    }
+    return lexer_token(lexer, TokenTypeId, pos);
+}
+
+Token lexer_lex_hashtag(Lexer* lexer)
+{
+    lexer_step(lexer);
+    while (!lexer_done(lexer) && lexer->current != '\n') {
+        lexer_step(lexer);
+    }
+    return lexer_next(lexer);
+}
+
+Token lexer_skip_whitespace(Lexer* lexer)
+{
+    lexer_step(lexer);
+    while (true) {
+        switch (lexer->current) {
+            case ' ':
+            case '\t':
+            case '\r':
+            case '\n':
+                lexer_step(lexer);
+                break;
+            default:
+                goto break_loop;
+        }
+    }
+break_loop:
+    return lexer_next(lexer);
+}
+
+Token lexer_token(const Lexer* lexer, TokenType type, Pos pos)
+{
+    return (Token) { type, pos, .length = lexer->pos.index - pos.index };
+}
+
+void lexer_step(Lexer* lexer)
+{
+    if (lexer->current == '\n') {
+        lexer->pos.line += 1;
+        lexer->pos.col = 1;
+    } else if (!lexer_done(lexer)) {
+        lexer->pos.col += 1;
+    }
+    lexer->current = lexer->reader->next(lexer->reader);
+}
+
+bool lexer_done(const Lexer* lexer) { return lexer->current == '\0'; }

src/lexer.h

@@ -1,4 +1,144 @@
 #ifndef LEXER_H
 #define LEXER_H
 
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define PANIC(...)                                                             \
+    (fprintf(stderr, "panic: "),                                               \
+     fprintf(stderr, __VA_ARGS__),                                             \
+     fprintf(stderr, ", at %s:%d in %s()", __FILE__, __LINE__, __func__),      \
+     exit(1));
+
+#define ASSERT(CONDITION)                                                      \
+    {                                                                          \
+        if (!(CONDITION)) {                                                    \
+            (fprintf(stderr, "assert failed: "),                               \
+             fprintf(                                                          \
+                 stderr,                                                       \
+                 "(%s), at %s:%d in %s()",                                     \
+                 #CONDITION,                                                   \
+                 __FILE__,                                                     \
+                 __LINE__,                                                     \
+                 __func__                                                      \
+             ),                                                                \
+             exit(1));                                                         \
+        }                                                                      \
+    };
+
+typedef struct {
+    const char* data;
+    size_t length;
+} StringSlice;
+
+bool string_slice_equal(StringSlice slice, const char* data);
+
+typedef struct {
+    char* data;
+    size_t length;
+    size_t capacity;
+} String;
+
+void string_construct(String* string);
+void string_destroy(String* string);
+void string_from_cstr(String* string, const char* value);
+void string_from_slice(String* string, StringSlice slice);
+void string_append_char(String* string, char value);
+void string_append_cstr(String* string, const char* value);
+void string_append_formatted(String* string, const char* format, ...);
+bool string_equal(const String* string, const char* value);
+
+typedef struct CharReader {
+    char (*next)(struct CharReader* reader);
+    StringSlice (*value)(
+        const struct CharReader* reader, size_t index, size_t length
+    );
+} CharReader;
+
+typedef struct FileCharReader {
+    char (*next)(struct FileCharReader* reader);
+    StringSlice (*value)(
+        const struct FileCharReader* reader, size_t index, size_t length
+    );
+    FILE* file;
+    String buffer;
+} FileCharReader;
+
+void file_char_reader_construct(FileCharReader* reader, FILE* file);
+void file_char_reader_destroy(FileCharReader* reader);
+char file_char_reader_next(FileCharReader* reader);
+StringSlice file_char_reader_value(
+    const FileCharReader* reader, size_t index, size_t length
+);
+
+typedef struct {
+    size_t index;
+    size_t line;
+    size_t col;
+} Pos;
+
+typedef struct {
+    Pos pos;
+    String message;
+} Error;
+
+void error_construct(Error* error, Pos pos, String message);
+void error_destroy(Error* error);
+
+typedef struct {
+    Error* errors;
+    size_t errors_length;
+    size_t errors_capacity;
+} ErrorCollector;
+
+void error_collector_construct(ErrorCollector* collector);
+void error_collector_destroy(ErrorCollector* collector);
+void error_collector_add(ErrorCollector* collector, Error error);
+
+typedef enum {
+    TokenTypeEof,
+    TokenTypeError,
+    TokenTypeId,
+    TokenTypeInt,
+    TokenTypeChar,
+    TokenTypeString,
+    TokenTypeLParen,
+    TokenTypeRParen,
+    TokenTypeLBrace,
+    TokenTypeRBrace,
+    TokenTypeLBracket,
+    TokenTypeRBracket,
+} TokenType;
+
+const char* token_type_value(TokenType type);
+
+typedef struct {
+    TokenType type;
+    Pos pos;
+    size_t length;
+} Token;
+
+typedef struct {
+    CharReader* reader;
+    ErrorCollector* errors;
+    char current;
+    Pos pos;
+} Lexer;
+
+Lexer lexer_create(CharReader* reader, ErrorCollector* errors);
+Token lexer_next(Lexer* lexer);
+
+Token lexer_lex_id(Lexer* lexer);
+Token lexer_lex_int(Lexer* lexer);
+Token lexer_lex_char(Lexer* lexer);
+Token lexer_lex_string(Lexer* lexer);
+Token lexer_lex_slash(Lexer* lexer);
+Token lexer_lex_hashtag(Lexer* lexer);
+Token lexer_skip_whitespace(Lexer* lexer);
+Token lexer_token(const Lexer* lexer, TokenType type, Pos pos);
+void lexer_step(Lexer* lexer);
+bool lexer_done(const Lexer* lexer);
+
 #endif

src/main.c

@@ -1,3 +1,5 @@
+#include "lexer.h"
+#include "parser.h"
 #include <stdio.h>
 
 int main(int argc, const char** argv)
@@ -14,11 +16,24 @@ int main(int argc, const char** argv)
         return 1;
     }
 
-    printf("file:\n");
-    int read_char = fgetc(file);
-    while (read_char != EOF) {
-        fputc(read_char, stdout);
-        read_char = fgetc(file);
-    }
-    fputc('\n', stdout);
+    ErrorCollector errors;
+    error_collector_construct(&errors);
+
+    FileCharReader reader;
+    file_char_reader_construct(&reader, file);
+
+    Lexer lexer = lexer_create((CharReader*)&reader, &errors);
+    Parser parser = parser_create((CharReader*)&reader, lexer, &errors);
+
+    ExprVec ast = parser_parse(&parser);
+
+    String ast_string;
+    string_construct(&ast_string);
+    expr_vec_stringify(&ast, &ast_string);
+    printf("ast = %s\n", ast_string.data);
+    string_destroy(&ast_string);
+
+    expr_vec_destroy(&ast);
+    file_char_reader_destroy(&reader);
+    error_collector_destroy(&errors);
 }

src/parser.c

@@ -0,0 +1,352 @@
+#include "parser.h"
+#include "lexer.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+void expr_vec_construct(ExprVec* vec)
+{
+    const size_t starting_capacity = 8;
+    *vec = (ExprVec) {
+        .exprs = malloc(starting_capacity * sizeof(Expr)),
+        .length = 0,
+        .capacity = starting_capacity,
+    };
+    ASSERT(vec->exprs);
+}
+void expr_vec_destroy(ExprVec* vec)
+{
+    for (size_t i = 0; i < vec->length; ++i) {
+        expr_destroy(&vec->exprs[i]);
+    }
+    free(vec->exprs);
+}
+
+void expr_vec_push(ExprVec* vec, Expr expr)
+{
+    if (vec->length >= vec->capacity) {
+        vec->capacity *= 2;
+        Expr* new_buffer = realloc(vec->exprs, vec->capacity * sizeof(Expr));
+        ASSERT(new_buffer);
+        vec->exprs = new_buffer;
+    }
+    vec->exprs[vec->length] = expr;
+    vec->length += 1;
+}
+
+void expr_vec_stringify(const ExprVec* vec, String* acc)
+{
+    string_append_cstr(acc, "[");
+    printf("helo worl\n");
+    if (vec->length > 0) {
+        expr_stringify(&vec->exprs[0], acc);
+        for (size_t i = 1; i < vec->length; ++i) {
+            string_append_cstr(acc, ", ");
+            expr_stringify(&vec->exprs[i], acc);
+        }
+    }
+    string_append_cstr(acc, "]");
+}
+
+Expr error_expr_construct(Pos pos)
+{
+    return (Expr) { ExprTypeError, pos, { 0 } };
+}
+
+Expr id_expr_construct(Pos pos, String value)
+{
+    return (Expr) { ExprTypeId, pos, .id_value = value };
+}
+
+Expr int_expr_construct(Pos pos, int64_t value)
+{
+    return (Expr) { ExprTypeInt, pos, .int_value = value };
+}
+
+Expr char_expr_construct(Pos pos, char value)
+{
+    return (Expr) { ExprTypeChar, pos, .char_value = value };
+}
+
+Expr string_expr_construct(Pos pos, String value)
+{
+    return (Expr) { ExprTypeString, pos, .string_value = value };
+}
+
+Expr list_expr_construct(Pos pos, ExprVec exprs)
+{
+    return (Expr) { ExprTypeList, pos, .list = exprs };
+}
+
+Expr quote_expr_construct(Pos pos, ExprVec exprs)
+{
+    return (Expr) { ExprTypeQuote, pos, .quote = exprs };
+}
+
+void expr_destroy(Expr* expr)
+{
+    switch (expr->type) {
+        case ExprTypeError:
+            break;
+        case ExprTypeId:
+            string_destroy(&expr->id_value);
+            break;
+        case ExprTypeInt:
+        case ExprTypeChar:
+            break;
+        case ExprTypeString:
+            string_destroy(&expr->string_value);
+            break;
+        case ExprTypeList:
+            expr_vec_destroy(&expr->list);
+            break;
+        case ExprTypeQuote:
+            expr_vec_destroy(&expr->quote);
+            break;
+    }
+}
+
+void expr_stringify(const Expr* expr, String* acc)
+{
+    switch (expr->type) {
+        case ExprTypeError:
+            string_append_formatted(acc, "Error");
+            break;
+        case ExprTypeId:
+            string_append_formatted(acc, "Id(%s)", expr->id_value.data);
+            break;
+        case ExprTypeInt:
+            string_append_formatted(acc, "Int(\'%ld\')", expr->int_value);
+            break;
+        case ExprTypeChar:
+            string_append_formatted(acc, "Char(\'%c\')", expr->char_value);
+            break;
+        case ExprTypeString:
+            string_append_formatted(
+                acc, "String(\"%s\")", expr->string_value.data
+            );
+            break;
+        case ExprTypeList:
+            string_append_cstr(acc, "List(");
+            if (expr->list.length > 0) {
+                expr_stringify(&expr->list.exprs[0], acc);
+                for (size_t i = 1; i < expr->list.length; ++i) {
+                    string_append_cstr(acc, ", ");
+                    expr_stringify(&expr->list.exprs[i], acc);
+                }
+            }
+            string_append_cstr(acc, ")");
+            break;
+        case ExprTypeQuote:
+            string_append_cstr(acc, "Quote(");
+            if (expr->quote.length > 0) {
+                expr_stringify(&expr->quote.exprs[0], acc);
+                for (size_t i = 1; i < expr->quote.length; ++i) {
+                    string_append_cstr(acc, ", ");
+                    expr_stringify(&expr->quote.exprs[i], acc);
+                }
+            }
+            string_append_cstr(acc, ")");
+            break;
+    }
+}
+
+#define PARSER_ADD_ERROR(PARSER, POS, ...)                                     \
+    {                                                                          \
+        String error_message;                                                  \
+        string_construct(&error_message);                                      \
+        string_append_formatted(&error_message, __VA_ARGS__);                  \
+        Error error;                                                           \
+        error_construct(&error, (POS), error_message);                         \
+        error_collector_add((PARSER)->errors, error);                          \
+    }
+
+Parser
+parser_create(const CharReader* reader, Lexer lexer, ErrorCollector* errors)
+{
+    Token first = lexer_next(&lexer);
+    return (Parser) {
+        .reader = reader,
+        .lexer = lexer,
+        .errors = errors,
+        .current = first,
+    };
+}
+
+ExprVec parser_parse(Parser* parser)
+{
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    while (parser->current.type != TokenTypeEof) {
+        expr_vec_push(&exprs, parser_parse_expr(parser));
+    }
+    return exprs;
+}
+
+Expr parser_parse_expr(Parser* parser)
+{
+    Pos pos = parser->current.pos;
+    switch (parser->current.type) {
+        case TokenTypeId:
+            return parser_parse_id(parser);
+        case TokenTypeInt:
+            return parser_parse_int(parser);
+        case TokenTypeChar:
+            return parser_parse_char(parser);
+        case TokenTypeString:
+            return parser_parse_string(parser);
+        case TokenTypeLParen:
+            return parser_parse_list(parser);
+        case TokenTypeLBracket:
+            return parser_parse_quote(parser);
+        default:
+            PARSER_ADD_ERROR(
+                parser,
+                pos,
+                "expected value, got `%s`",
+                token_type_value(parser->current.type)
+            );
+            parser_step(parser);
+            return error_expr_construct(pos);
+    }
+}
+
+Expr parser_parse_id(Parser* parser)
+{
+    Token token = parser->current;
+    String value;
+    string_from_slice(
+        &value,
+        parser->reader->value(parser->reader, token.pos.index, token.length)
+    );
+    parser_step(parser);
+    return id_expr_construct(token.pos, value);
+}
+
+Expr parser_parse_int(Parser* parser)
+{
+    Token token = parser->current;
+    String text;
+    string_from_slice(
+        &text,
+        parser->reader->value(parser->reader, token.pos.index, token.length)
+    );
+    int64_t value = atol(text.data);
+    string_destroy(&text);
+    parser_step(parser);
+    return int_expr_construct(token.pos, value);
+}
+
+Expr parser_parse_char(Parser* parser)
+{
+    Token token = parser->current;
+    StringSlice text
+        = parser->reader->value(parser->reader, token.pos.index, token.length);
+    char value = text.data[1];
+    if (value == '\\') {
+        switch (text.data[2]) {
+            case '0':
+                value = '\0';
+                break;
+            case 't':
+                value = '\t';
+                break;
+            case 'r':
+                value = '\r';
+                break;
+            case 'n':
+                value = '\n';
+                break;
+            default:
+                value = text.data[2];
+                break;
+        }
+    }
+    parser_step(parser);
+    return char_expr_construct(token.pos, value);
+}
+
+Expr parser_parse_string(Parser* parser)
+{
+    Token token = parser->current;
+    StringSlice text
+        = parser->reader->value(parser->reader, token.pos.index, token.length);
+    String value;
+    string_construct(&value);
+    for (size_t i = 1; i < text.length - 2; ++i) {
+        if (text.data[i] == '\\') {
+            i += 1;
+            switch (text.data[i]) {
+                case '0':
+                    string_append_char(&value, '\0');
+                    break;
+                case 't':
+                    string_append_char(&value, '\t');
+                    break;
+                case 'r':
+                    string_append_char(&value, '\r');
+                    break;
+                case 'n':
+                    string_append_char(&value, '\n');
+                    break;
+                default:
+                    string_append_char(&value, text.data[i]);
+                    break;
+            }
+        } else {
+            string_append_char(&value, text.data[i]);
+        }
+    }
+    parser_step(parser);
+    return string_expr_construct(token.pos, value);
+}
+
+Expr parser_parse_list(Parser* parser)
+{
+    Pos pos = parser->current.pos;
+    parser_step(parser);
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    while (parser->current.type != TokenTypeEof
+           && parser->current.type != TokenTypeRParen) {
+        expr_vec_push(&exprs, parser_parse_expr(parser));
+    }
+    if (parser->current.type != TokenTypeRParen) {
+        PARSER_ADD_ERROR(
+            parser,
+            pos,
+            "expected `]`, got `%s`",
+            token_type_value(parser->current.type)
+        )
+    } else {
+        parser_step(parser);
+    }
+    return quote_expr_construct(pos, exprs);
+}
+
+Expr parser_parse_quote(Parser* parser)
+{
+    Pos pos = parser->current.pos;
+    parser_step(parser);
+    ExprVec exprs;
+    expr_vec_construct(&exprs);
+    while (parser->current.type != TokenTypeEof
+           && parser->current.type != TokenTypeRBracket) {
+        expr_vec_push(&exprs, parser_parse_expr(parser));
+    }
+    if (parser->current.type != TokenTypeRBracket) {
+        PARSER_ADD_ERROR(
+            parser,
+            pos,
+            "expected `]`, got `%s`",
+            token_type_value(parser->current.type)
+        )
+    } else {
+        parser_step(parser);
+    }
+    return quote_expr_construct(pos, exprs);
+}
+
+void parser_step(Parser* parser)
+{
+    parser->current = lexer_next(&parser->lexer);
+}

src/parser.h

@@ -0,0 +1,75 @@
+#ifndef PARSER_H
+#define PARSER_H
+
+#include "lexer.h"
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+typedef enum {
+    ExprTypeError,
+    ExprTypeId,
+    ExprTypeInt,
+    ExprTypeChar,
+    ExprTypeString,
+    ExprTypeList,
+    ExprTypeQuote,
+} ExprType;
+
+typedef struct Expr Expr;
+
+typedef struct {
+    Expr* exprs;
+    size_t length;
+    size_t capacity;
+} ExprVec;
+
+void expr_vec_construct(ExprVec* vec);
+void expr_vec_destroy(ExprVec* vec);
+void expr_vec_push(ExprVec* vec, Expr expr);
+void expr_vec_stringify(const ExprVec* vec, String* acc);
+
+struct Expr {
+    ExprType type;
+    Pos pos;
+    union {
+        String id_value;
+        int64_t int_value;
+        char char_value;
+        String string_value;
+        ExprVec list;
+        ExprVec quote;
+    };
+};
+
+Expr error_expr_construct(Pos pos);
+Expr id_expr_construct(Pos pos, String value);
+Expr int_expr_construct(Pos pos, int64_t value);
+Expr char_expr_construct(Pos pos, char value);
+Expr string_expr_construct(Pos pos, String value);
+Expr list_expr_construct(Pos pos, ExprVec exprs);
+Expr quote_expr_construct(Pos pos, ExprVec exprs);
+void expr_destroy(Expr* expr);
+void expr_stringify(const Expr* expr, String* acc);
+
+typedef struct {
+    const CharReader* reader;
+    Lexer lexer;
+    ErrorCollector* errors;
+    Token current;
+} Parser;
+
+Parser
+parser_create(const CharReader* reader, Lexer lexer, ErrorCollector* errors);
+ExprVec parser_parse(Parser* parser);
+
+Expr parser_parse_expr(Parser* parser);
+Expr parser_parse_id(Parser* parser);
+Expr parser_parse_int(Parser* parser);
+Expr parser_parse_char(Parser* parser);
+Expr parser_parse_string(Parser* parser);
+Expr parser_parse_list(Parser* parser);
+Expr parser_parse_quote(Parser* parser);
+void parser_step(Parser* parser);
+
+#endif

test.ol

@@ -0,0 +1 @@
+(fn sum (a b) (+ a b))