Priority

[Vito Corleone]

Hi,

If I write:
return $x || undef();

Which will be executed first? Is it:
(return $x) || undef();

or
return ($x || undef());

Thank you.
Vito

 

[Sam Holden]

Hi,

If I write:
return $x || undef();

Which will be executed first? Is it:
(return $x) || undef();

or
return ($x || undef());

The later.

The former can be achieved by using the lower precedence 'or':

return $x or undef();

But that's useless (I don't think there is a situation in which
return can fail - and in which the code compiles).

 

[J. Romano]

If I write:
return $x || undef();
Which will be executed first? Is it:
(return $x) || undef();
or
return ($x || undef());

Dear Vito,

Sometimes it's not immediately clear how Perl will parse an
expression. In cases like these, I use the "-MO=Deparse,-p" switch,
like this:

# In UNIX:
perl -MO=Deparse,-p -e 'sub { return $x || undef(); }'

# In DOS:
perl -MO=Deparse,-p -e "sub { return $x || undef(); }"

(I put your expression inside a subroutine in order to make the
one-liner compile.)

The output of this command shows the line:

return(($x || undef()));

signifying that your second guess is correct.

Hope this helps,

-- Jean-Luc

 

[Michele Dondi]

Hi,

If I write:
return $x || undef();

Which will be executed first? Is it:
(return $x) || undef();

or
return ($x || undef());

perldoc perlop

and/or, as another poster already suggested,

perl -MO=Deparse,-p


HTH,
Michele