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#include "Calculator.h"
#include <ctype.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static char logic_log[4096];
typedef struct {
const char *buffer;
int pos;
} Parser;
static double parse_expression(Parser *p);
static void skip_ws(Parser *p) {
while (p->buffer[p->pos] == ' ')
p->pos++;
}
static double parse_factor(Parser *p) {
skip_ws(p);
if (p->buffer[p->pos] == '-') {
p->pos++;
return -parse_factor(p);
}
if (p->buffer[p->pos] == '(') {
p->pos++;
double res = parse_expression(p);
if (p->buffer[p->pos] == ')')
p->pos++;
return res;
}
char *endptr;
double val = strtod(&p->buffer[p->pos], &endptr);
p->pos = (int)(endptr - p->buffer);
return val;
}
static double parse_term(Parser *p) {
double left = parse_factor(p);
while (1) {
skip_ws(p);
char op = p->buffer[p->pos];
if (op == '*' || op == '/') {
p->pos++;
double right = parse_factor(p);
double old = left;
left = (op == '*') ? left * right : left / right;
char step[256];
snprintf(step, sizeof(step), "<div>%g %c %g = <b>%g</b></div>", old, op,
right, left);
strncat(logic_log, step, sizeof(logic_log) - strlen(logic_log) - 1);
} else
break;
}
return left;
}
static double parse_expression(Parser *p) {
double left = parse_term(p);
while (1) {
skip_ws(p);
char op = p->buffer[p->pos];
if (op == '+' || op == '-') {
p->pos++;
double right = parse_term(p);
double old = left;
left = (op == '+') ? left + right : left - right;
char step[256];
snprintf(step, sizeof(step), "<div>%g %c %g = <b>%g</b></div>", old, op,
right, left);
strncat(logic_log, step, sizeof(logic_log) - strlen(logic_log) - 1);
} else
break;
}
return left;
}
double evaluate(const char *expr) {
logic_log[0] = '\0';
if (!expr || strlen(expr) == 0)
return 0.0;
Parser p = {expr, 0};
return parse_expression(&p);
}
InfoBox fetch_calc_data(char *math_input) {
InfoBox info = {NULL, NULL, NULL, NULL};
if (!math_input)
return info;
double result = evaluate(math_input);
char html_output[5120];
snprintf(html_output, sizeof(html_output),
"<div class='calc-container' style='line-height: 1.6;'>"
"%s"
"<div style='margin-top: 8px; border-top: 1px solid #eee; "
"padding-top: 8px; font-size: 1.2em;'>"
"<b>%g</b>"
"</div>"
"</div>",
strlen(logic_log) > 0 ? logic_log : "<div>Constant value</div>",
result);
info.title = strdup("Calculation");
info.extract = strdup(html_output);
info.thumbnail_url = strdup("/static/calculation.svg");
info.url = strdup("#");
return info;
}
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