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

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This topic contains 3 replies, has 4 voices, and was last updated by  HubertK7641 7 years, 3 months ago.

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  • March 3, 2010 at 6:31 pm #2244

    WeldonGarrison
    Member

    #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
    Member

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

  • April 5, 2012 at 3:10 pm #3643

    PSBMaira490593
    Member

    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
    Member

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