diff options
| -rw-r--r-- | 4/6.c | 216 |
1 files changed, 216 insertions, 0 deletions
@@ -0,0 +1,216 @@ +#include <ctype.h> +#include <math.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#define MAXOP 100 /* max size of operand or operator */ +#define NUMBER '0' /* signal that a number was found */ +#define FUNCTION '1' /* signal that a custom op was found */ +#define ASSIGNMENT '2' /* signal that a variable was found */ +#define VARIABLE '3' /* signal that a variable was found */ +#define MAXVAL 100 /* max depth of val and var stack */ +#define BUFSIZE 100 +#define VARCOUNT \ + 26 /* supported variable count. Upper case letters reserved \ + */ + +int sp = 0; /* next free stack position */ +double val[MAXVAL]; /* value stack */ + +int vidx = 0; /* variable array position */ +char varn[VARCOUNT]; /* variable name array */ +double varv[VARCOUNT]; /* variable value array */ + +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 for sin, exp and pow functions */ +int main(int argc, char *argv[]) { + int type, i, var; + 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 FUNCTION: + if (strcmp("top", s) == 0) + peek(); + else if (strcmp("dup", s) == 0) + push(peek()); + else if (strcmp("swp", s) == 0) { + op2 = pop(); + op1 = pop(); + push(op2); + push(op1); + } else if (strcmp("cls", s) == 0) + clear(); + else if (strcmp("sin", s) == 0) + push(sin(pop())); + else if (strcmp("exp", s) == 0) + push(exp(pop())); + else if (strcmp("pow", s) == 0) + push(pow(pop(), pop())); + else + printf("error: unknown function %s\n", s); + break; + case ASSIGNMENT: + varn[vidx] = s[0]; + varv[vidx++] = pop(); + break; + case VARIABLE: + var = 0; + for (i = 0; i < vidx; i++) { + if (varn[i] == s[0]) { + var = 1; + push(varv[i]); + break; + } + } + if (!var) + printf("error: unknown symbol %s\n", s); + 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, nc, rv; + + while ((s[0] = c = getch()) == ' ' || c == '\t') + ; + s[1] = 0; + + // operators or line feed + if (c == '\n' || c == '+' || c == '*' || c == '/' || c == '%') + return c; + + i = 0; + + // numbers + if (isdigit(c) || c == '-') { + // minus operator + if (c == '-' && !isdigit(s[++i] = c = getch())) { + ungetch(c); + s[i] = 0; + return '-'; + } + + while (isdigit(s[++i] = c = getch()) || c == '.') + ; + rv = NUMBER; + } else { + // functions and variables + int count; + for (count = 0; isalnum(s[++i] = c = getch()); count++) + ; + + if (count == 0) { + // syntax "5 A =" means "A = 5" + if ((nc = getch()) == '=') + rv = ASSIGNMENT; + else { + ungetch(c); + ungetch(nc); + rv = VARIABLE; + } + } else { + rv = FUNCTION; + } + } + + s[i] = 0; + + if (c != EOF) + ungetch(c); + + return rv; +} |