Re: to paren or not to paren

[kcott]

G'day quixadhal,

When in doubt, you can check how Perl will parse your code fragment from the command line, rather than having to run a (test) script, with this:

perl -MO=Deparse,-p -e '... code fragment here ...'

See B::Deparse for more information about this.

"In most cases, I find I can happily write code which calls functions without needing to use those pesky parenthesis, other than to clarify which arguments are being passed, and which are part of another expression." [my emphasis]

Clarification is exactly what's needed here. Perl doesn't know if you meant

$self->selector->remove($self)->listener;

or

$self->selector->remove($self->listener);

Notice in the following what's valid and invalid syntax:

$ perl -MO=Deparse,-p -e '$self->selector->remove $self->listener;'
Scalar found where operator expected at -e line 1, near "->remove $sel
+f"
    (Missing operator before $self?)
syntax error at -e line 1, near "->remove $self"
-e had compilation errors.

$ perl -MO=Deparse,-p -e '$self->selector->remove($self)->listener;'
$self->selector->remove($self)->listener;
-e syntax OK

$ perl -MO=Deparse,-p -e '$self->selector->remove($self->listener);'
$self->selector->remove($self->listener);
-e syntax OK

For more information about calling methods, see perlobj. In particular, these three sections of that documentation:

• Method Invocation
• Method Call Variations
• Invoking Class Methods [Especially noting the strongly discouraged Indirect Object Syntax]