101 lines
1.6 KiB
C
101 lines
1.6 KiB
C
#include <stdio.h>
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#include <stdbool.h>
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#include "stack.h"
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bool isWhitespace(char c)
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{
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return(c == ' ' || c == '\t' || c == '\n' || c == '\r' );
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}
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char *eatAllWhitespaces(char *At)
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{
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while(*At && isWhitespace(*At))
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At++;
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return At;
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}
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bool isDigit(char Digit)
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{
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return (Digit >= '0' && Digit <= '9');
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}
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int isNumber(char *Number)
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{
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int Result = 0;
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while(*Number && *Number != ' ')
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{
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if(!isDigit(*Number))
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{
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Result = -1;
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return Result;
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}
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Number++;
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Result++;
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}
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return Result;
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}
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int main(int argc, char **argv)
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{
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stack Stack = {};
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float Result = 0;
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//
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// Parsing
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//
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//char *Input = "6 3 + 4 - 20 *";
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char *Input = argv[1];
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char *At = Input;
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while(*At)
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{
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At = eatAllWhitespaces(At);
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switch(*At)
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{
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case '+':
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{
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float Addent1 = pop(&Stack);
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float Addent2 = pop(&Stack);
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push(&Stack, Addent1 + Addent2);
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}break;
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case '-':
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{
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float Subtrahend = pop(&Stack);
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float Minuend = pop(&Stack);
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push(&Stack, Minuend - Subtrahend);
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}break;
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case '*':
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{
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float Multiplicand = pop(&Stack);
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float Multiplier = pop(&Stack);
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push(&Stack, Multiplier * Multiplicand);
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}break;
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case '/':
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{
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float divisor = pop(&Stack);
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float dividend = pop(&Stack);
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push(&Stack, dividend / divisor);
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}break;
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default:
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{
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int Length = isNumber(At);
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if(Length != -1)
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{
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push(&Stack, atof(At));
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At += Length -1;
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}
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else
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{
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printf("ERROR: Only Numbers and Operators + - * and / are allowed");
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}
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}
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}
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At++;
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}
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while(peak(&Stack))
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{
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printf("%f ", pop(&Stack));
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}
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printf("\n");
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}
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