plzzz help…….it doesn’t evaluate right……!

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    • March 3, 2010 at 6:31 pm #2244
      WeldonGarrison
      Participant

      #include
      #include

      #define MAX 50
      #define EMPTY -1

      struct stack
      {
      int data[MAX];
      int top;
      };

      int isempty(struct stack *s)
      {
      return (s->top == EMPTY) ? 1 : 0;
      }

      void emptystack(struct stack* s)
      {
      s->top = EMPTY;
      }

      void push(struct stack* s,int item)
      {
      if(s->top == (MAX-1))
      {
      printf(“nSTACK FULL”);
      }
      else
      {
      ++s->top;
      s->data[s->top]=item;
      }
      }

      int pop(struct stack* s)
      {
      int ret=EMPTY;
      if(s->top == EMPTY)
      printf(“nSTACK EMPTY”);
      else
      {
      ret= s->data[s->top];
      –s->top;
      }
      return ret;
      }

      void display(struct stack s)
      {
      while(s.top != EMPTY)
      {
      printf(“n%d”,s.data[s.top]);
      s.top–;
      }
      }

      int isoperator(char e)
      {
      if(e == ‘+’ || e == ‘-‘ || e == ‘*’ || e == ‘/’ || e == ‘%’)
      return 1;
      else
      return 0;
      }

      int priority(char e)
      {
      int pri = 0;

      if(e == ‘*’ || e == ‘/’ || e ==’%’)
      pri = 2;
      else
      {
      if(e == ‘+’ || e == ‘-‘)
      pri = 1;
      }
      return pri;
      }

      int evaluate(char *postfix)
      {
      char *p;
      struct stack stk;
      int op1,op2,result;

      emptystack(&stk);
      p = &postfix[0];

      while(*p != ‘’)
      {
      /* removes tabs and spaces */
      while(*p == ‘ ‘ || *p == ‘t’)
      {
      p++;
      }
      /* if is digit */
      if(isdigit(*p))
      {
      push(&stk,*p – 48);
      }
      else
      {
      /* it is an operator */
      op2 = pop(&stk);
      op1 = pop(&stk);

      switch(*p)
      {
      case ‘+’:
      result = op1 + op2;
      break;

      case ‘-‘:
      result = op1 – op2;
      break;

      case ‘/’:
      result = op1 / op2;
      break;

      case ‘*’:
      result = op1 * op2;
      break;

      case ‘%’:
      result = op1 % op2;
      break;

      default:
      printf(“nInvalid Operator”);
      return 0;
      }
      push(&stk,result);
      }
      p++;
      }
      result = pop(&stk);
      return result;
      }

      void infix2postfix(char* infix, char * postfix, int insertspace)
      {
      char *i,*p;
      struct stack X;
      char n1;
      emptystack(&X);
      i = &infix[0];
      p = &postfix[0];

      while(*i)
      {
      while(*i == ‘ ‘ || *i == ‘t’)
      {
      i++;
      }

      if( isdigit(*i) || isalpha(*i) )
      {
      while( isdigit(*i) || isalpha(*i))
      {
      *p = *i;
      p++;
      i++;
      }
      /*SPACE CODE*/
      if(insertspace)
      {
      *p = ‘ ‘;
      p++;
      }
      /*END SPACE CODE*/
      }

      if( *i == ‘(‘ )
      {
      push(&X,*i);
      i++;
      }

      if( *i == ‘)’)
      {
      n1 = pop(&X);
      while( n1 != ‘(‘ )
      {
      *p = n1;
      p++;
      /*SPACE CODE*/
      if(insertspace)
      {
      *p = ‘ ‘;
      p++;
      }
      /*END SPACE CODE*/
      n1 = pop(&X);
      }
      i++;
      }

      if( isoperator(*i) )
      {
      if(isempty(&X))
      push(&X,*i);
      else
      {
      n1 = pop(&X);
      while(priority(n1) >= priority(*i))
      {
      *p = n1;
      p++;
      /*SPACE CODE*/
      if(insertspace)
      {
      *p = ‘ ‘;
      p++;
      }
      /*END SPACE CODE*/
      n1 = pop(&X);
      }
      push(&X,n1);
      push(&X,*i);
      }
      i++;
      }
      }
      while(!isempty(&X))
      {
      n1 = pop(&X);
      *p = n1;
      p++;
      /*SPACE CODE*/
      if(insertspace)
      {
      *p = ‘ ‘;
      p++;
      }
      /*END SPACE CODE*/
      }
      *p = ‘’;
      }

      int main(void)
      {
      char infix[MAX], postfix[MAX], result[MAX];
      printf(“Enter expression: “);
      fflush(stdin);
      gets(infix);
      infix2postfix(&infix[0],&postfix[0],1);
      printf(“nPostfix expression is: %s”,&postfix[0]);
      result[0]=postfix[0];
      printf(“n %s = %d.”,&infix[0],evaluate(&result[0]));
      return 0;
      }

      Code:

    • March 5, 2010 at 11:20 pm #3642
      GWILouisaxwzkla
      Participant

      Heres a postfix to infix program I have on my drive ( hope this helps….. ):

    • April 5, 2012 at 3:10 pm #3643
      PSBMaira490593
      Participant

      Hi,
      please run it again in new window and check the variable that you have declared are right or not.
      thanks.


      Debra Fine

    • April 9, 2012 at 11:31 pm #3644
      HubertK7641
      Participant

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