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postfix2real.c
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/*
* Please see README for copying information.
*/
#include <math.h>
#include <curses.h>
#include <ctype.h>
#include <string.h>
#define MAX_NUM_SCALARS 100
/*
void main() {
double x = 2.0;
double y = 2.0;
double postfix2real(double, double , char *);
printf("%lf + %lf = %lf\n", x, y, f(x, y, "xy+"));
printf("%lf - %lf = %lf\n", x, y, f(x, y, "xy-"));
printf("%lf * %lf = %lf\n", x, y, f(x, y, "xy*"));
printf("%lf / %lf = %lf\n", x, y, f(x, y, "xy/"));
printf("%lf ^ %lf = %lf\n", x, y, f(x, y, "xy^"));
printf("sin(%lf) = %lf\n", x, f(x, y, "xs"));
printf("cos(%lf) = %lf\n", x, f(x, y, "xc"));
printf("exp(%lf) = %lf\n", x, f(x, y, "xe"));
printf("log(%lf) = %lf\n", x, f(x, y, "xl"));
printf("-(%lf) = %lf\n", x, f(x, y, "xn"));
printf("abs(%lf) = %lf\n", x, f(x, y, "xa"));
printf("sqrt(%lf) = %lf\n", x, f(x, y, "xq"));
}
*/
double postfix2real(double x, double y, char f[100])
{
double char2double(char f[100], int *i);
double scalar_stack[MAX_NUM_SCALARS];
int num_scalars=0;
double a, b;
double result;
int i;
for (i=0; i<strlen(f); i++)
{
if (isdigit(f[i])) result = char2double(f, &i);
else switch (tolower(f[i]))
{
case 'x': result = x;
break;
case 'y': result = y;
break;
case '+': a = scalar_stack[num_scalars-1];
num_scalars--;
b = scalar_stack[num_scalars-1];
num_scalars--;
result = b + a;
break;
case '-': a = scalar_stack[num_scalars-1];
num_scalars--;
b = scalar_stack[num_scalars-1];
num_scalars--;
result = b - a;
break;
case '*': a = scalar_stack[num_scalars-1];
num_scalars--;
b = scalar_stack[num_scalars-1];
num_scalars--;
result = b * a;
break;
case '/': a = scalar_stack[num_scalars-1];
num_scalars--;
b = scalar_stack[num_scalars-1];
num_scalars--;
result = b / a;
break;
case 's': a = scalar_stack[num_scalars-1];
num_scalars--;
result = sin(a);
break;
case 'c': a = scalar_stack[num_scalars-1];
num_scalars--;
result = cos(a);
break;
case '^': a = scalar_stack[num_scalars-1];
num_scalars--;
b = scalar_stack[num_scalars-1];
num_scalars--;
result = pow(b,a);
break;
case 'e': a = scalar_stack[num_scalars-1];
num_scalars--;
result = exp(a);
break;
case 'l': a = scalar_stack[num_scalars-1];
num_scalars--;
if (a<=0) a=1;
result = log(a);
break;
case 'n': a = scalar_stack[num_scalars-1];
num_scalars--;
result = -a;
break;
case 'a': a = scalar_stack[num_scalars-1];
num_scalars--;
result = fabs(a);
break;
case 'q': a = scalar_stack[num_scalars-1];
num_scalars--;
if (a<0) {
result = 0.0;
} else {
result = sqrt(a);
}
break;
}
#ifdef DEBUG_POSTFIX
printf("scalar_stack[%i] = %lf\n", num_scalars, result);
#endif
scalar_stack[num_scalars] = result;
num_scalars++;
}
if (num_scalars > 1) printf("ERROR!!\n");
return scalar_stack[0];
}
double char2double(char f[100], int *i)
{
double x;
sscanf(f+(*i), "%lf", &x);
*i = strlen(f) - strlen(strchr(f+(*i), '#')+1) - 1;
/*
printf("i in = %i\n", *i);
printf("string = %s\n", f);
printf("x = %lf\n", x);
printf("the rest = %s\n", strchr(f+(*i), '#')+1);
printf("length = %i\n", strlen(f));
printf("i out = %i\n", *i);
*/
return x;
}