variable processing and checking in one statement

[saunderson]

Hi all,

i wonder whether it's possible to simplify constructs like

doSthWith($test) if checkFn($test);

further, such that i have to write the variable ($test) only once!?

I often have to deal with such statements and i just don't want to use perl's default variable, so that it yields

$_=$test; doSthWith($_) if checkFn($_);

since $_ is often used by other statements in the same block.

How would you monks do it the neat way?

best regards

[tye]

for my $t ( $test ) {
    doWith($t)
        if  check($t);
}

avoids $_ completely. Clearly not worth it if your variable is actually just $test.

[saunderson]

Thank you for your contribution. the for respectively the foreach approach will cetrainly find their ways in my future scripts ...

[BrowserUk]

You could do:

checkFn( $_ ) and doSthWith( $_ ) for $test;

which wouldn't interfere with surrounding uses of $_; and avoids referencing $test twice.

But I wouldn't unless the variable in question was a complex reference. Ie. a multi-level hash or array lookup.

[ig]

How about

doSthWith(checkFn($test));

Have checkFn return the passed data if all is well, or undef if not and have doSthWith check its arguments.

Or, incorporate the check into doSthWith - depending on where you want to localize the knowledge about the condition, and how you want to handle the race between the check and what you do with $test

And, I don't advocate this but find the range of possibilities interesting and can't seem to stop myself from updating:

sub {
    doSthWith($_[0])
        if(checkFn($_[0]));
}->($test);