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#include <stdio.h>
#include "parser/parser.h"
struct Parser
{
struct Lexer* lexer;
struct Token current;
struct Token previous;
bool had_error;
};
static void advance_parser(struct Parser* parser)
{
parser->previous = parser->current;
parser->current = scan_token(parser->lexer);
}
static bool check(struct Parser* parser, enum TokenType type)
{
return parser->current.type == type;
}
static void error_at(struct Parser* parser, struct Token token, const char* message)
{
fprintf(stderr, "error: line %u: %s\n", token.line, message);
parser->had_error = true;
}
static bool consume(struct Parser* parser, enum TokenType type, const char* message)
{
if (check(parser, type))
{
advance_parser(parser);
return true;
}
error_at(parser, parser->current, message);
return false;
}
static bool parse_const(struct Parser* parser, struct Program* program)
{
struct ConstDecl decl;
if (!consume(parser, TOKEN_IDENTIFIER, "expected constant name after 'const'"))
return false;
decl.name = parser->previous;
if (!consume(parser, TOKEN_EQUAL, "expected '=' after constant name"))
return false;
if (!consume(parser, TOKEN_INTEGER, "expected integer value after '='"))
return false;
decl.value = parser->previous;
add_const(program, decl);
return true;
}
bool parse_program(struct Lexer* lexer, struct Program* out)
{
struct Parser parser;
parser.lexer = lexer;
parser.had_error = false;
advance_parser(&parser);
*out = create_program();
while (!check(&parser, TOKEN_EOF))
{
if (check(&parser, TOKEN_CONST))
{
advance_parser(&parser);
if (!parse_const(&parser, out))
return false;
}
else
{
error_at(&parser, parser.current, "expected a top-level declaration");
return false;
}
}
return !parser.had_error;
}
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