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Re: New Discovery!!! (sub call without parentheses)

by eyepopslikeamosquito (Chancellor)
on Dec 08, 2018 at 17:46 UTC ( #1226973=note: print w/replies, xml ) Need Help??


in reply to New Discovery!!! (sub call without parentheses)

I always use parens when calling user-defined subroutines and methods because:

  • The consistency of always using parens when calling user-defined subroutines/methods makes the code easier to read (for me).
  • Code tends to be more robust if it is reorganized in the future. For example, if you later switch from use (compile-time) to require (run-time) (to speed initial module load or when porting to a new platform, say) your code may break in surprising ways. Even if you can "easily" fix the code to use parens (so that it will parse correctly with require), doing so risks breaking what might be thousands of lines of working production code ... so avoid that future risk by always using parens in the first place.

This is essentially the same advice given in Perl Best Practices, Chapter 9, "Subroutines" in the "Call subroutines with parentheses but without a leading &" item.

See also: to paren or not to paren

  • Comment on Re: New Discovery!!! (sub call without parentheses)

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Re^2: New Discovery!!! (sub call without parentheses)
by stevieb (Canon) on Dec 08, 2018 at 23:00 UTC

    Two very good points there.

    I always use parens on my user-defined functions whether I've got parameters or not. Kind of a habit actually now that I'm fluent in more than just a couple of languages, most of which enforce using parens. In fact, thinking about it, I think Perl's the only language which *doesn't* enforce parens if a function is pre-declared. Also, at a glance (at least with my own code), it's easier to identify built-ins, as I typically don't use parens for them (eg: sleep 10;).

    The only time I'll leave parens off of a call, is if it's a method call where I'm not sending in any params:

    my $object = My::Thing->new(speak => 'hi'); ... $object->speak;
      > I think Perl's the only language which doesn't enforce parens if a function is pre-declared

      Ruby never does, but probably you wanted to say "if and only if" ?

      The possibility to omit parenthesis is essential for many syntactic sugar and DSL approaches.

      Compare "has" in Moose which looks like a keyword.

      update

      example

      has 'first_name' => ( is => 'rw', isa => 'Str', );

      Cheers Rolf
      (addicted to the Perl Programming Language :)
      Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

Re^2: New Discovery!!! (sub call without parentheses)
by LanX (Archbishop) on Dec 08, 2018 at 19:25 UTC
    Yes, but with exceptions.

    When designing syntactic sugar and/or DSLs its useful to leave the parentheses off.

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

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