Do you prefer “if (var)” or “if (var != 0)”? [closed]

Answer 1

There are languages in which you have no choice. In Specman, for instance, you can't write:

var x: uint;

if (x) {
    bla
};

But you can do:

var x: uint;

if (x != 0) {
    bla
};

or

var x: bool;

if (x) {
    bla
};

However, you can't do:

var x: bool;

if (x != 0) {
    bla
};

Because you can't compare a boolean to an integer.

Coming from C and Perl I always thought this to be annoying, until I actually started writing a lot in Specman. The code is simply clearer like this.

Answer 2

In Perl if (defined $var and $var ne '') and if( $var) are NOT equivalent. Try it with $var=0. Conversely if you test on $var!=0 all strings that cannot be converted to numbers will fail the test (with a warning if you have them on).

So you must know exactly what your variable contains (number or string, whether it can be undef) so you can test accordingly.

I usually just write if( $var) and let Perl take care it. I believe that's easier to read, and that's the most common style in Perl.

Very often, actually, the proper test ends up being if( defined $var). That's where perl's new (in 5.10) // operator comes in handy. $var= $val // $default or often $var //= $default, where $var will receive $default only if $val (resp $var) is undef.

Answer 3

In Javascript (I don't know about other dynamic languages)

if (x) 

and

if (x != 0)

mean different things. I will use the former when the I expect x to hold a reference to an object or string that should not be zero length. Its a well known enough idiom.

Answer 4

In C# it has been made explicitly illegal to write

if(x){}

unless x is a boolean type. There is no implicit conversion to bool from most other types.

I used this form a lot writing JavaScript, PHP and such to check for non null. But then again, I did get a few (easily detectable) bugs from it... I guess we are better off without it.

When using it on boolean variables, I strongly believe in easily readable names. I usually name boolean variables used like that with names beginning with "is", "has" or something similar.

Answer 5

I find that if(X) { /* ... */ } is much easier to read (in C, at least).

Answer 6

if (var)

Less to type, as long as you're sure you're not testing the wrong thing.