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fixed gitignore and added comments to parser

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This commit is contained in:
Lorenzo Torres 2025-12-01 10:16:35 +01:00
parent 3efd9c8295
commit 26ae74cc87
2 changed files with 22 additions and 1 deletions
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2
.gitignore vendored
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@ -1,3 +1,3 @@
**/*.o **/*.o
**/*~ **/*~
cc lc

21
parser.c
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@ -4,6 +4,7 @@
ast_node *parse_expression(parser *p); ast_node *parse_expression(parser *p);
/* Consume a token in the list. */
static void advance(parser *p) static void advance(parser *p)
{ {
p->previous = p->tokens; p->previous = p->tokens;
@ -11,11 +12,16 @@ static void advance(parser *p)
p->tokens = p->tokens->next; p->tokens = p->tokens->next;
} }
/* Get the current token in the list, without consuming */
static token *peek(parser *p) static token *peek(parser *p)
{ {
return p->tokens; return p->tokens;
} }
/*
* Check if the current token type is the same as `type`,
* without consuming it.
*/
static bool match_peek(parser *p, token_type type) static bool match_peek(parser *p, token_type type)
{ {
if (p->tokens) { if (p->tokens) {
@ -25,6 +31,7 @@ static bool match_peek(parser *p, token_type type)
} }
} }
/* Same as `match_peek()` but it consumes the token. */
static bool match(parser *p, token_type type) static bool match(parser *p, token_type type)
{ {
if (p->tokens) { if (p->tokens) {
@ -36,6 +43,13 @@ static bool match(parser *p, token_type type)
return false; return false;
} }
/*
* When an error is encountered, try to find a
* token that could define a part of the code
* which doesn't depend on the one giving the
* error. This is needed to print multiple errors
* instead of just failing at the first one.
*/
static void parser_sync(parser *p) static void parser_sync(parser *p)
{ {
advance(p); advance(p);
@ -61,12 +75,14 @@ static void parser_sync(parser *p)
} }
} }
/* Print the error message and sync the parser. */
static void error(parser *p, char *msg) static void error(parser *p, char *msg)
{ {
printf("\x1b[31m\x1b[1merror\x1b[0m\x1b[1m:%ld:%ld:\x1b[0m %s\n", p->previous->position.row, p->previous->position.column, msg); printf("\x1b[31m\x1b[1merror\x1b[0m\x1b[1m:%ld:%ld:\x1b[0m %s\n", p->previous->position.row, p->previous->position.column, msg);
parser_sync(p); parser_sync(p);
} }
/* Parse expressions with the highest precedence. */
static ast_node *parse_factor(parser *p) static ast_node *parse_factor(parser *p)
{ {
token *t = peek(p); token *t = peek(p);
@ -184,6 +200,10 @@ ast_node *parse_term(parser *p)
return left; return left;
} }
/*
* Following the recursive descent parser algorithm, this
* parses all the arithmetic expressions.
*/
ast_node *parse_expression(parser *p) ast_node *parse_expression(parser *p)
{ {
ast_node *left = parse_term(p); ast_node *left = parse_term(p);
@ -203,6 +223,7 @@ ast_node *parse_expression(parser *p)
return left; return left;
} }
/* Get a list of expressions to form a full AST. */
static void parse(parser *p) static void parse(parser *p)
{ {
p->ast = arena_alloc(p->allocator, sizeof(ast_node)); p->ast = arena_alloc(p->allocator, sizeof(ast_node));