static struct term *_lambda_parse(struct lexer *lex, enum term_parse_res *res)
{
struct term *body = NULL;
struct term *ret = NULL;
if(lex->type != TOK_SYM) {
*res = PARSE_EXPECTED_SYM;
goto done;
} else {
char var[VAR_LEN];
strncpy(var, lex->sym, VAR_LEN);
lexer_advance(lex);
if(lex->type != TOK_DOT) {
*res = PARSE_EXPECTED_DOT;
goto done;
}
lexer_advance(lex);
body = _term_parse(lex, res);
if(! body) {
goto done;
}
ret = make_lambda(var, body);
}
done:
destroy_term(body);
return ret;
}
static struct term *_term_parse(struct lexer *lex, enum term_parse_res *res)
{
struct term *ret = NULL;
switch(lex->type) {
case TOK_NONE:
*res = PARSE_EXPECTED_TERM;
break;
case TOK_LPAREN:
lexer_advance(lex);
ret = _lparen_parse(lex, res);
break;
case TOK_RPAREN:
*res = PARSE_UNEXPECTED_RPAREN;
break;
case TOK_LAMBDA:
lexer_advance(lex);
ret = _lambda_parse(lex, res);
break;
case TOK_DOT:
*res = PARSE_UNEXPECTED_DOT;
break;
case TOK_SYM:
ret = make_var(lex->sym);
lexer_advance(lex);
break;
}
return ret;
}
static struct term *_lparen_parse(struct lexer *lex, enum term_parse_res *res)
{
struct term *term1 = NULL;
struct term *term2 = NULL;
struct term *ret = NULL;
term1 = _term_parse(lex, res);
if(! term1) {
goto done;
}
if(lex->type != TOK_RPAREN) {
term2 = _term_parse(lex, res);
if(! term2) {
goto done;
}
if(lex->type != TOK_RPAREN) {
*res = PARSE_EXPECTED_RPAREN;
goto done;
}
lexer_advance(lex);
ret = make_appl(term1, term2);
} else {
lexer_advance(lex);
ret = term1;
term1 = NULL;
}
done:
destroy_term(term1);
destroy_term(term2);
return ret;
}
struct term *term_parse(FILE *instream, enum term_parse_res *res)
{
struct lexer lex = { .stream = instream, .type = TOK_NONE };
*res = PARSE_OK;
lexer_advance(&lex);
return _term_parse(&lex, res);
}
token_t * lexer_peek(lexer_t *l) {
if (!l)
return NULL;
list_node_t *n = l->curtok;
token_t *t = lexer_advance(l);
l->curtok = n;
return t;
}
