Expr* term_tail(const char* string, Expr* expr) {
Expr* new_expr;
switch(string[VAL_STRING]) {
case '+':
case '-':
if(NULL == (new_expr = (Expr*)malloc(sizeof(Expr)))) {
exit(1);
}
if(NULL == (new_expr->data.expr[1] = (Expr*)malloc(sizeof(Expr)))) {
exit(1);
}
new_expr->op = eat_char(string, string[VAL_STRING]);
new_expr->data.expr[0] = expr;
new_expr->data.expr[1] = term(string, new_expr->data.expr[1]);
new_expr = term_tail(string, new_expr);
return new_expr;
case ')':
case 0:
return expr;
default:
error_message(string);return NULL;
}
}
static exp_node *expression(void){
exp_node *expn = newExpNode();
if(match(TOKEN_LBRA, NO_CONSUME) ||
match(TOKEN_IDENTIFIER, NO_CONSUME) ||
match(TOKEN_LITERAL, NO_CONSUME))
if((expn->termn = term()) != NULL)
if((expn->termtln = term_tail()) != error)
return expn;
freeExp(expn);
return NULL;
}
Expr* parse(const char* string) {
Expr* expr;
if(string[VAL_STRING] == '(' || isdigit(string[VAL_STRING])) {
if(NULL == (expr = (Expr*)malloc(sizeof(Expr)))) {
exit(1);
}
expr = term(string, expr);
expr = term_tail(string, expr);
return expr;
} else {
error_message(string);return NULL;
}
}
static term_tail_node *term_tail(void){
term_tail_node *termtln = newTermTailNode();
if((termtln->addOp = match(TOKEN_ADDOP, CONSUME)) != NULL){
if((termtln->termn = term()) != NULL)
if((termtln->termtln = term_tail()) != error)
return termtln;
}
else if(match(TOKEN_RBRA, NO_CONSUME) ||
match(TOKEN_SCOL, NO_CONSUME) ||
match(TOKEN_COMPOP, NO_CONSUME)){
freeTermTail(termtln);
return NULL;
}
freeTermTail(termtln);
return error;
}
