CODEWITHSUNDEEP
c++logicboolean
JDN
JDN

Reputation: 519

Boolean logic issue

I was wondering if there was a shorter way to write 

if (test != 'e' || test != 'd')

I want to write it like

if (test != ('e' || 'd'))

Or something like this so i don't have to repeat "test !="

Thanks

Upvotes: 1

Views: 146

Answers (3)

Jeff D.
Jeff D.

Reputation: 328

C or C++ must evaluate the expressions you write in the syntax of the language. The expression ('e' or 'd') always returns true because the 'or-ing' is done by comparing the bits of the values which will never be the same. How is the compiler to know what you want since in C/C++ a raw character is simply an interpretation of an integer. That's why you can legally write:

char aChar = 'a';
// or
char aChar = 0x41; // hex 41 = ascii 'a'

and have them both work.

Upvotes: 0

Oleksi
Oleksi

Reputation: 13097

That's the syntax of the language. There's not much you can do about it... If you don't like the way it looks, you can make a boolean function that contains the tests and then just call that function:

bool isEOrD(char test)
{
    return (test != 'e' || test != 'd')
}

...

if (isEOrD(test))

EDIT: There are other ways to write this code (see the comments to this answer), but your original way is probably the cleanest approach.

Upvotes: 2

dreamlax
dreamlax

Reputation: 95315

You could use the old C function strchr:

if (!strchr("de", test))
{
    // test is not 'd' or 'e'
}

But I don't know whether it is any nicer to look at… personally I would probably just have the two !=.

Upvotes: 1

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