diff options
| -rw-r--r-- | 4/5.c | 218 |
1 files changed, 218 insertions, 0 deletions
@@ -0,0 +1,218 @@ + +#include <ctype.h> +#include <math.h> +#include <stdio.h> +#include <stdlib.h> + +#define MAXOP 100 /* max size of operand or operator */ +#define NUMBER '0' /* signal that a number was found */ +#define MAXVAL 100 /* max depth of val stack */ +#define BUFSIZE 100 + +int sp = 0; /* next free stack position */ +double val[MAXVAL]; /* value stack */ + +int bufp = 0; /* next free position in buf */ +char buf[BUFSIZE]; /* buffer for ungetch */ + +/* get next operator or numeric operand */ +int getop(char[]); + +/* push f onto value stack */ +void push(double); + +/* pop and return top value from stack */ +double pop(); + +/* returns a value from stack without removing it */ +double peek(); + +/* clears the stack */ +void clear(); + +/* adds support sin, exp and power functions */ +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 '+': + 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: division by zero\n"); + break; + case '%': + op2 = pop(); + if (op2 != 0.0) + push((int)pop() % (int)op2); + else + printf("error: division by zero\n"); + break; + case 'p': + peek(); + break; + case 'c': + push(peek()); + break; + case 's': + op2 = pop(); + op1 = pop(); + push(op2); + push(op1); + break; + case 'd': + clear(); + break; + case 'S': + push(sin(pop())); + break; + case 'P': + push(pow(pop(), pop())); + break; + case 'E': + push(exp(pop())); + break; + case '\n': + printf("\t%.8g\n", pop()); + break; + default: + printf("error: unknown command %s\n", s); + } + } + + return 0; +} + +void push(double f) { + if (sp < MAXVAL) + val[sp++] = f; + else + printf("error: stack empty\n"); +} + +double pop() { + if (sp > 0) + return val[--sp]; + else { + printf("error: stack empty\n"); + return 0.0; + } +} + +double peek() { + if (sp > 0) + return val[sp - 1]; + else { + printf("error: stack empty\n"); + return 0.0; + } +} + +void clear() { + for (; sp > 0; sp--) + ; +} + +int getch() { return (bufp > 0) ? buf[--bufp] : getchar(); } + +void ungetch(int c) { + if (bufp >= BUFSIZE) + printf("ungetch: too many characters\n"); + else + buf[bufp++] = c; +} + +int getop(char s[]) { + int i, c; + + while ((s[0] = c = getch()) == ' ' || c == '\t') + ; + s[1] = 0; + + if (!isdigit(c) && c != '.' && c != '-' && c != 's' && c != 'p' && c != 'e') + return c; + + i = 0; + if (isdigit(c)) + while (isdigit(s[++i] = c = getch())) + ; + if (c == '.') + while (isdigit(s[++i] = c = getch())) + ; + if (c == '-') + while (isdigit(s[++i] = c = getch())) + ; + // sin or swap function + if (c == 's') { + if ((c = getch()) == ' ') + return 's'; + else if (c == 'i') { + if ((c = getch()) == 'n') { + return 'S'; + } else { + ungetch(c); + ungetch('i'); + return 's'; + } + } else { + ungetch(c); + return 's'; + } + } + + // power function + if (c == 'p') { + if ((c = getch()) == 'o') { + if ((c = getch()) == 'w') { + return 'P'; + } else { + ungetch(c); + ungetch('o'); + return 'p'; + } + } else { + ungetch(c); + return 'p'; + } + } + + // exponent function + if (c == 'e') { + if ((c = getch()) == 'x') { + if ((c = getch()) == 'p') { + return 'E'; + } else { + ungetch(c); + ungetch('x'); + return 'e'; + } + } else { + ungetch(c); + return 'e'; + } + } + + s[i] = 0; + + if (c != EOF) + ungetch(c); + + return NUMBER; +} |