CODEWITHSUNDEEP
ccalculator
Eskang
Eskang

Reputation: 1

Calculator in C - limiting input values

So I've got an assignment in school, to building a calculator. The program should consist of a "parcer.c"-file where all the not allowed inputs are sorted out, and if any unallowed values and inputs are submitted it should give you back a "Syntax Error" -message.

i've got it done, only one thing left, and it's this, a if that's supposed to check and make sure that the sizeof (op) is not bigger than 1, meaning that it can only consist of 1 sign(+,-,,/,%) But my problem is that i still can write; 4 +sdf 5 and get the result = 9 But i cant write 4sdf 5 or 4 sdf 5, becuse then I get my "Syntax Error", which is correct.

What should i turn around to give me the same error when I've got junk after the operator? EX: 4 +sdf 5 

if(sizeof (*op) > 1 || !validOperator(op))
    {
        //Returns statuscode 2 and a "Syntax Error" if the operator 

          is consisting of more than 1 sign

        printf("\n Syntax Error, only +, -, x, /, %% are allowed\n");
        return 2;
    }

Upvotes: 0

Views: 62

Answers (1)

Ivan Angelov
Ivan Angelov

Reputation: 353

I assume op is defined as

char *op; /*or maybe as char op[]*/

When you check with sizeof(*op) you check the size of the first element in the array of chars, i.e. it will always return 1.

You want to use strlen() instead of sizeof(). Try following change:

if( op!=0 && (strlen(*op) > 1 || !validOperator(op)) )

Upvotes: 1

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