r4/expression-parser
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simplification by use of macros (hopefully)

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r4 2021-11-22 21:22:07 +01:00
parent 0fcef2a860
commit dacf01e83e
1 changed files with 9 additions and 7 deletions
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16
main.c
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@ -35,6 +35,7 @@ uint8_t op_prec[256] = {
['/'] = 2,
['^'] = 3,
};
#define OP_PREC(tok_char) (op_prec[(size_t)tok_char])
enum {
OrderLtr,
@ -48,6 +49,7 @@ enum {
['/'] = OrderLtr,
['^'] = OrderRtl,
};
#define OP_ORDER(tok_char) (op_order[(size_t)tok_char])
#define IS_FLOAT(c) ((c >= '0' && c <= '9') || c == '.')
#define IS_ALPHA(c) ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'))
@ -166,7 +168,7 @@ void del_toks(Tok *begin, Tok *end) {
}
real eval(Tok *t) {
if (!(t[0].kind == TokOp && op_prec[(size_t)t[0].Char] == 0)) {
if (!(t[0].kind == TokOp && OP_PREC(t[0].Char) == 0)) {
fprintf(stderr, "Error: expected delimiter at beginning of expression\n");
exit(1);
}
@ -186,7 +188,7 @@ 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 && op_prec[(size_t)t[i].Char] == 0); i++);
for (i = 2; !(t[i].kind == TokOp && OP_PREC(t[i].Char) == 0); i++);
del_toks(t + 2, t + i + 1);
/* Put the newly evaluated value into place. */
t[1].kind = TokNum;
@ -208,7 +210,7 @@ real eval(Tok *t) {
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++);
for (; !(t[i].kind == TokOp && OP_PREC(t[i].Char) == 0); i++);
bool end = t[i].Char == ')';
if (t[i].Char == ',')
del_toks(t, t + i);
@ -246,18 +248,18 @@ real eval(Tok *t) {
}
const char curr_op = t[0].Char;
const uint8_t curr_prec = op_prec[(size_t)curr_op];
const uint8_t curr_prec = OP_PREC(curr_op);
const char next_op = t[2].Char;
const uint8_t next_prec = op_prec[(size_t)next_op];
const uint8_t next_prec = OP_PREC(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)) {
if (next_prec > curr_prec || (next_prec == curr_prec && OP_ORDER(curr_op) == OrderRtl)) {
t += 2;
} else if (next_prec < curr_prec || (next_prec == curr_prec && op_order[(size_t)curr_op] == OrderLtr)) {
} else if (next_prec < curr_prec || (next_prec == curr_prec && OP_ORDER(curr_op) == OrderLtr)) {
real res;
real lhs = t[-1].Num, rhs = t[1].Num;
switch (curr_op) {