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| -rw-r--r-- | 4/11.c | 152 |
1 files changed, 152 insertions, 0 deletions
@@ -0,0 +1,152 @@ +#include <ctype.h> +#include <math.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#define MAXOP 100 +#define HEIGHT 1000 + +#define NUM '0' +#define FUN '1' +#define VAR '2' + +#define INDEX(x) (x <= 'Z' ? x - 'A' : x - 71) /* index of the variable */ + +char var[52]; +double lout = 0.0; + +int getop(char[]); +void push(double); +double pop(); +double peek(); +void clear(); + +/* Stack based reverse Polish notation calculator without ungetch() + - single uppercase and lowercase characters are variables (syntax 2 A =); + - special variable LOUT for the last printed value. + - mathematical functions: sin, cos, tan, exp, pow. + - custom functions: swp (swap top 2 values), dup (duplicate last value), + top (peek at the stack top), cls (clear stack). + - operators: +, -, *, /, % and =. + - press enter to print the value at the top of the stack. + */ +int main(int argc, char *argv[]) { + int type; + double op1, op2; + char s[MAXOP]; + + while ((type = getop(s)) != 0) { + switch (type) { + case NUM: + push(atof(s)); + break; + case '+': + op1 = pop(); + op2 = pop(); + push(op1 + op2); + break; + case '-': + op2 = pop(); + op1 = pop(); + push(op1 - op2); + break; + case '*': + op2 = pop(); + op1 = pop(); + push(op1 * op2); + break; + case '/': + op2 = pop(); + op1 = pop(); + if (op1 == 0.0) + printf("error: division by zero\n"); + else + push((double)op1 / op2); + break; + case '%': + op2 = pop(); + op1 = pop(); + if (op2 == 0.0) + printf("error: division by zero\n"); + else + push((int)op1 % (int)op2); + break; + case '=': + var[INDEX(s[0])] = pop(); + break; + case VAR: + if (strcmp("LOUT", s) == 0) + push(lout); + else + push(var[INDEX(s[0])]); + break; + case FUN: + if (strcmp("sin", s) == 0) + push(sin(pop())); + else if (strcmp("cos", s) == 0) + push(cos(pop())); + else if (strcmp("tan", s) == 0) + push(tan(pop())); + else if (strcmp("exp", s) == 0) + push(exp(pop())); + else if (strcmp("pow", s) == 0) + push(pow(pop(), pop())); + else if (strcmp("cls", s) == 0) + clear(); + else if (strcmp("top", s) == 0) { + lout = peek(); + printf("\t%.8g\n", lout); + } else if (strcmp("swp", s) == 0) { + op2 = pop(); + op1 = pop(); + push(op2); + push(op1); + } else if (strcmp("dup", s) == 0) + push(peek()); + else + printf("error: unknown function %s\n", s); + break; + case '\n': + lout = pop(); + printf("\t%.8g\n", lout); + break; + default: + printf("error: unknown command %s\n", s); + } + } + return 0; +} + +int sp = 0; +double stack[HEIGHT]; + +void push(double f) { + if (sp < HEIGHT) + stack[sp++] = f; + else + printf("error: stack empty\n"); +} + +double pop() { + if (sp > 0) + return stack[--sp]; + else { + printf("error: stack empty\n"); + return 0.0; + } +} + +double peek() { + if (sp > 0) + return stack[sp - 1]; + else { + printf("error: stack empty\n"); + return 0.0; + } +} + +void clear() { + for (; sp > 0; sp--) + ; +}
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