.ccls-cache
main
main.c
Makefile
Config files
.replit
replit.nix
/**
* Exercise 4.5 from The C Programming Language by Brian Kernighan and Dennis
* Ritchie
*
* Add access to library functions like sin, exp, and pow. See <math.h> in
* Appendix B, Section 4.
*/
#include <math.h> /* for math functions */
#include <stdio.h>
#include <stdlib.h> /* for atof() */
#define MAXOP 100 /* max size of operand or operator */
#define NUMBER '0' /* signal that a number was found */
#define NAME 'n' /* signal that a name was found */
int getop(char[]);
void push(double);
double pop(void);
void mathfnc(char[]);
void clearsp(void);
int main(int argc, char *argv[]) {
int type;
double op2, op1;
char s[MAXOP];
while ((type = getop(s)) != EOF) {
switch (type) {
case NUMBER:
push(atof(s));
break;
case NAME:
mathfnc(s);
break;
case '+':
push(pop() + pop());
break;
case '*':
push(pop() * pop());
break;
case '-':
op2 = pop();
push(pop() - op2);
break;
case '/':
op2 = pop();
if (op2 != 0.0)
push(pop() / op2);
else
printf("error: zero divisor\n");
break;
case '%':
op2 = pop();
if (op2 != 0.0)
push(fmod(pop(), op2));
else
printf("error: zero divisor\n");
break;
case '?':
op2 = pop();
printf("\t%.8g\n", op2);
push(op2);
break;
case 'c':
clearsp();
break;
case 'd':
op2 = pop();
push(op2);
push(op2);
break;
case 's':
op1 = pop();
op2 = pop();
push(op1);
push(op2);
break;
case '\n':
printf("\t%.8g\n", pop());
break;
default:
printf("error: unknown command %s\n", s);
break;
}
}
return 0;
}
#define MAXVAL 100 /* maximum depth of val stack */
int sp = 0; /* next free stack position */
double val[MAXVAL]; /* value stack */
/* push: push f onto value stack */
void push(double f) {
if (sp < MAXVAL)
val[sp++] = f;
else
printf("error: stack full, can't push %g\n", f);
}
/* pop: pop and return top value from stack */
double pop(void) {
if (sp > 0)
return val[--sp];
else {
printf("error: stack empty\n");
return 0.0;
}
}
void clearsp(void) { sp = 0; }
#include <ctype.h>
#include <string.h>
int getch(void);
void ungetch(int);
/* getop: get next operator or numeric operand */
int getop(char s[]) {
int i, c;
static int lastc = 0;
if (lastc == 0)
c = getch();
else {
c = lastc;
lastc = 0;
}
while ((s[0] = c) == ' ' || c == '\t')
c = getch();
s[1] = '\0';
i = 0;
if (islower(c)) {
while (islower(s[++i] = c = getch()))
;
s[i] = '\0';
if (c != EOF)
lastc = c;
if (strlen(s) > 1)
return NAME;
else
return c;
}
if (!isdigit(c) && c != '.' && c != '-')
return c; /* not a number */
if (c == '-') {
if (isdigit(c = getch()) || c == '.')
s[++i] = c; /* negative number */
else {
if (c != EOF)
lastc = c;
return '-'; /* minus sign */
}
}
if (isdigit(c)) /* collect integer part */
while (isdigit(s[++i] = c = getch()))
;
if (c == '.') /* collect fraction part */
while (isdigit(s[++i] = c = getch()))
;
s[i] = '\0';
if (c != EOF)
lastc = c;
return NUMBER;
}
#define BUFSIZE 100
char buf[BUFSIZE]; /* buffer for ungetch */
int bufp = 0; /* next free position in buf */
int getch(void) { /* get a (possibly pushed back) character */
return (bufp > 0) ? buf[--bufp] : getchar();
}
void ungetch(int c) { /* push character back on input */
if (bufp >= BUFSIZE)
printf("ungetch: too many characters\n");
else
buf[bufp++] = c;
}
void mathfnc(char s[]) {
double op2;
if (strcmp(s, "sin") == 0)
push(sin(pop()));
else if (strcmp(s, "cos") == 0)
push(cos(pop()));
else if (strcmp(s, "exp") == 0)
push(exp(pop()));
else if (strcmp(s, "pow") == 0) {
op2 = pop();
push(pow(pop(), op2));
} else
printf("error: %s not supported\n", s);
}