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postfix evaluation

 
 
maha_khaled maha_khaled is offline
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Join Date: Apr 2012
Location: Egypt
Posts: 1
 
      04-19-2012
Hi, i'am trying to read postfix expression from txt file and evaluate it
the input is 10 5 * ,the output should be 50, but it reads only 10 and 5,the problem he can't read operators neither their ascii ,any help?
here's my code
PHP Code:
#include <iostream> #include <iomanip> #include <fstream> #include<stdio.h> #include<ctype.h> #include<stdlib.h> using namespace std; #define SIZE 40 int stack[SIZE]; int top=-1; void push(int n) { if(top==SIZE-1) { printf("Stack is full\n");  system("pause"); return; } else { top=top+1; stack[top]=n; printf("Pushed element is %d\n",n);  system("pause"); } } int pop() { int n; if(top==-1) { printf("Stack is empty\n");  system("pause"); return 0; } else { n=stack[top]; top=top-1; return(n); } } int main() { int str[50],ch; int i=0; int n,op1,op2; ifstream inFile; ch=str[i]; inFile.open("D:\\me.txt"); if (!inFile) { printf( "Unable to open file"); system("pause"); exit(1); // terminate with error } while (inFile >> ch) { if(ch==43 || ch==45 || ch==47 || ch==42 || ch==94 || ch==37 ) {     op1=pop();     op2=pop();     if (op1<op2)     {     n=op1;     op1=op2;     op2=n;     }     switch(ch)     {     case 43:     n=op1+op2; break;     case 45:     n=op1-op2;break;     case 42:     n=op1*op2;break;     case 47:     n=op1/op2;break;     case 37:     n=op1%op2;break;     case 94:     n=op1^op2;break;          default:     {     printf("The operator is not identified\n");     system("pause");     exit(0);break;     }     }     printf("n=%d\n",n);     push(n);     system("pause"); }     else     {     n=ch;     push(n);     } ch=str[++i]; }inFile.close(); printf("The value of the arithmetic expression is=%d\n",pop()); system("pause"); return 0; } 
 
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