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expression-parser
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basic multi-parameter functions

This commit is contained in:
r4 2021-11-21 18:59:31 +01:00
parent d1cf60794d
commit dfc515b7df
1 changed files with 37 additions and 15 deletions
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52
main.c
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@ -26,8 +26,9 @@ Tok toks[TOKS_CAP];
size_t toks_size = 0;
uint8_t op_prec[256] = {
['('] = 0,
['('] = 0, /* A precedence of 0 is reserved for delimiters. */
[')'] = 0,
[','] = 0,
['+'] = 1,
['-'] = 1,
['*'] = 2,
@ -118,6 +119,7 @@ void tokenize(char *expr) {
switch (c) {
case '(':
case ')':
case ',':
case '+':
case '-':
case '*':
@ -172,8 +174,8 @@ void del_toks(Tok *begin, Tok *end) {
}
real eval(Tok *t) {
if (!(t[0].kind == TokOp && t[0].Char == '(')) {
fprintf(stderr, "Error: expected '(' at beginning of expression\n");
if (!(t[0].kind == TokOp && op_prec[(size_t)t[0].Char] == 0)) {
fprintf(stderr, "Error: expected delimiter at beginning of expression\n");
exit(1);
}
@ -182,7 +184,7 @@ real eval(Tok *t) {
if (t[1].kind == TokOp && t[1].Char == '(') {
real res = eval(t + 1);
size_t i;
for (i = 2; !(t[i].kind == TokOp && t[i].Char == ')'); i++);
for (i = 2; !(t[i].kind == TokOp && op_prec[(size_t)t[i].Char] == 0); i++);
del_toks(t + 2, t + i + 1);
/* Put the newly evaluated value into place. */
t[1].kind = TokNum;
@ -192,29 +194,48 @@ real eval(Tok *t) {
/* Collapse function. */
if (t[1].kind == TokFunc) {
print_toks();
if (!(t[2].kind == TokOp && t[2].Char == '(') || t + 2 >= toks + toks_size) {
if (t + 2 >= toks + toks_size || !(t[2].kind == TokOp && t[2].Char == '(')) {
fprintf(stderr, "Error: expected '(' token after function\n");
exit(1);
}
real inner_res = eval(t + 2);
size_t i;
for (i = 3; !(t[i].kind == TokOp && t[i].Char == ')'); i++);
del_toks(t + 2, t + i + 1);
real arg_results[16];
size_t arg_results_size = 0;
t += 2;
while (1) {
arg_results[arg_results_size++] = eval(t); /* TODO: Overflow protection. */
size_t i = 1;
for (; !(t[i].kind == TokOp && op_prec[(size_t)t[i].Char] == 0); i++);
bool end = t[i].Char == ')';
if (t[i].Char == ',')
del_toks(t, t + i);
else if (t[i].Char == ')')
del_toks(t, t + i + 1);
if (end)
break;
}
t -= 2;
real outer_res;
if (strcmp(t[1].Str, "sqrt") == 0) {
outer_res = sqrt(inner_res);
if (arg_results_size != 1) {
fprintf(stderr, "Error: function sqrt() requires exactly 1 argument\n");
exit(1);
}
outer_res = sqrt(arg_results[0]);
} else if (strcmp(t[1].Str, "pow") == 0) {
if (arg_results_size != 2) {
fprintf(stderr, "Error: function pow() requires exactly 2 arguments\n");
exit(1);
}
outer_res = pow(arg_results[0], arg_results[1]);
} else {
fprintf(stderr, "Error: unknown function name: %s\n", t[1].Str);
exit(1);
}
t[1].kind = TokNum;
t[1].Num = outer_res;
print_toks();
}
if (!(t[0].kind == TokOp && t[1].kind == TokNum && t[2].kind == TokOp)) {
@ -228,7 +249,8 @@ real eval(Tok *t) {
const char next_op = t[2].Char;
const uint8_t next_prec = op_prec[(size_t)next_op];
if (curr_op == '(' && next_op == ')')
/* Delimiters have a precedence of 0; if we have a number between two delimiters, we're done. */
if (curr_prec == 0 && next_prec == 0)
return t[1].Num;
if (next_prec > curr_prec || (next_prec == curr_prec && op_order[(size_t)curr_op] == OrderRtl)) {