r4/expression-parser
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

apply negative prefix in parser

Browse Source 
Previously a negative prefix was applied in the lexer, but that's kind
of hacky and messy so I handed it to the parser.
This commit is contained in:
r4 2021-11-22 20:56:06 +01:00
parent dfc515b7df
commit 0fcef2a860
1 changed files with 12 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
main.c
View File

@ -62,15 +62,12 @@ void tokenize(char *expr) {
size_t paren_depth = 0;
bool can_be_neg_num = true;
char *curr = expr;
for (char c = *curr; c != 0; c = *(++curr)) {
if (c == ' ')
continue;
if (IS_FLOAT(c) ||
(can_be_neg_num && c == '-' && IS_FLOAT(curr[1]))) {
if (IS_FLOAT(c)) {
char buf[16];
buf[0] = c;
size_t i = 1;
@ -84,8 +81,6 @@ void tokenize(char *expr) {
real num = strtod(buf, NULL);
push_tok((Tok){.kind = TokNum, .Num = num});
can_be_neg_num = false;
continue;
}
@ -101,8 +96,6 @@ void tokenize(char *expr) {
buf[i++] = 0;
push_tok((Tok){.kind = TokFunc, .Str = buf});
can_be_neg_num = false;
continue;
}
@ -132,8 +125,6 @@ void tokenize(char *expr) {
fprintf(stderr, "Error: unrecognized token at %zd: '%c'\n", curr - expr, c);
exit(1);
}
can_be_neg_num = c != ')';
}
if (paren_depth > 0) {
@ -168,6 +159,7 @@ void print_toks() {
printf("\n");
}
/* Delete tokens from begin to end (excluding end itself). */
void del_toks(Tok *begin, Tok *end) {
memmove(begin, end, (toks_size - (end - toks)) * sizeof(Tok));
toks_size -= end - begin;
@ -180,6 +172,16 @@ real eval(Tok *t) {
}
while (1) {
/* Collapse factor. */
if (t[1].kind == TokOp && t[1].Char == '-') {
if (t[2].kind != TokNum) {
fprintf(stderr, "Error: expected number token after minus factor\n");
exit(1);
}
t[2].Num *= -1.0;
del_toks(t + 1, t + 2);
}
/* Collapse parentheses. */
if (t[1].kind == TokOp && t[1].Char == '(') {
real res = eval(t + 1);