You are using the wrong or there. It will work often, except where it causes hard to find bugs. Instead, use || for "OR" expressions. Use or for control of flow, and || for expressions that evaluate to a value, as a general rule of thumb. The issue is the low precedence of or, which will trick you sometimes.

So the first code snippet above could be written as:

$var = $var || 30;
# or
$var ||= 30;
# or
$var = $var ? $var : 30;
# or if you care about definedness rather than Boolean truth:
$var = $var // 30;
# or
#var //= 30;
# or
$var = defined($var) ? $var : 30;

[download]

Your second code snippet is also probably broken, because undef $var will set $var to undef and will then evaluate the expression's value, which is now always going to be undef. You probably meant this: 

if (! defined $var) {
    $x = 40;
}
else {
    $x = 50;
}

[download]

Which might be written more elegantly like this: 

$x = defined $var ? 50 : 40;

[download]

For what it's worth, some of this applies equally in many languages such as C and C++. There's not really a concept of definedness in C/C++, but the concept of short circuiting in expressions using ||, and of ternary operators is nearly identical.


Dave

In reply to Re: Need clean code by davido
in thread Need clean code by ravi45722

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