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#include <stdio.h>
#include <stdlib.h>
#include "evalexpr.h"
enum assoc
{
NONE,
RIGHT,
LEFT,
};
int opcmp(struct token *op1, struct token *op2)
{
return op1->type - op2->type;
}
enum assoc get_assoc(struct token *op)
{
if (op->type == EXP)
{
return RIGHT;
}
return LEFT;
}
enum token_type get_type(char op)
{
switch (op)
{
case '*':
return MUL;
case '/':
return DIV;
case '-':
return SUB;
case '+':
return ADD;
case '%':
return MOD;
case '^':
return EXP;
case '(':
return PAR_LEFT;
case ')':
return PAR_RIGHT;
default:
return WRONG_TOKEN;
}
}
char *fifo_to_expr(struct fifo *output, size_t size_offset)
{
char *res = malloc((2 * fifo_size(output) + size_offset) * sizeof(char));
if (!res)
{
fifo_destroy(output);
return NULL;
}
res[2 * fifo_size(output) + size_offset - 1] = '\0';
size_t i = 0;
while (fifo_size(output) > 0)
{
if (fifo_head(output)->type == NUMBER)
{
i += sprintf(res + i, "%d", fifo_head(output)->value) - 1;
}
else
{
res[i] = fifo_head(output)->value;
}
fifo_pop(output);
i++;
if (fifo_size(output) != 0)
{
res[i] = ' ';
i++;
}
}
fifo_destroy(output);
return res;
}
int handle_rpar(struct tstack **opstack, struct fifo *output, struct token **t)
{
while (*opstack)
{
struct token *o2 = tstack_peek(*opstack);
if (o2->value == '(')
{
free(o2);
break;
}
*opstack = tstack_pop(*opstack);
fifo_push(output, o2);
}
if (*opstack == NULL)
{
free(*t);
fifo_destroy(output);
return 2;
}
free(*t);
*opstack = tstack_pop(*opstack);
return 0;
}
int empty_opstack(struct tstack **opstack, struct fifo *output)
{
while (*opstack)
{
struct token *t = tstack_peek(*opstack);
if (t->value == '(' || t->value == ')')
{
fifo_destroy(output);
return 1;
}
*opstack = tstack_pop(*opstack);
fifo_push(output, t);
}
return 0;
}
void pop_ops(struct tstack **opstack, struct fifo *output, struct token *t)
{
while (*opstack)
{
struct token *o2 = tstack_peek(*opstack);
if (!(o2->value != '('
&& (opcmp(t, o2) < 0
|| (opcmp(t, o2) == 0 && get_assoc(t) == LEFT))))
{
break;
}
*opstack = tstack_pop(*opstack);
fifo_push(output, o2);
}
}
void handle_numbers(struct fifo *output, size_t *i, int *size_offset,
const char *expr)
{
size_t offset;
int val = parse_number(expr + *i, &offset);
struct token *t = malloc(sizeof(struct token));
t->type = NUMBER;
t->value = val;
fifo_push(output, t);
*i += offset;
*size_offset += offset;
}
int shunting_yard(const char *expr, char **rpn)
{
struct fifo *output = fifo_init();
struct tstack *opstack = NULL;
int size_offset = 0;
for (size_t i = 0; expr[i]; i++)
{
if (expr[i] >= '0' && expr[i] <= '9')
{
handle_numbers(output, &i, &size_offset, expr);
}
else if (expr[i] != ' ')
{
struct token *t = malloc(sizeof(struct token));
t->value = expr[i];
if ((t->type = get_type(expr[i])) == WRONG_TOKEN)
{
free(t);
return 1;
}
if (t->value == '(')
{
opstack = tstack_push(opstack, t);
continue;
}
else if (t->value == ')')
{
if (handle_rpar(&opstack, output, &t) != 0)
return 2;
continue;
}
pop_ops(&opstack, output, t);
opstack = tstack_push(opstack, t);
}
}
if (empty_opstack(&opstack, output) != 0)
{
return 1;
}
*rpn = fifo_to_expr(output, size_offset);
if (!*rpn)
return 4;
return 0;
}
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