use Perl

• Example of why this is hard (Score:1)

  by Limbic Region (3985)

  For the benefit of others reading your journal that don't fully understand why this is probably not an easy thing to do....

  sub double { 2 * $_[0] }

  Seems straight forward enough and shouldn't have any side effects. Hrm, what if $_[0] is an alias to a tied variable. What if the FETCH method of that variable has action at a distance. Can't tell just by looking at the source :-(
  • Re: (Score:1)

    by DAxelrod (4649)

    Which is exactly why you'd at very least need the optree.
    
    Something Alias taught me with PPI is that analyzing Perl source is so dang hard partially because of the potentially hidden external factors that can change what a particular line means.
    
    What you've shown extremely well above is that a document parser is probably the wrong way to do side-effect analysis.
    • Re:Example of why this is hard (Score:1)

      by chromatic (983) on 2006.10.26 2:56 (#51273) Homepage Journal

      I don't think the optree holds that information, as it's the opcodes themselves that have to check for magic. At compile time, Perl doesn't know if you'll pass in a variable with magic.

      Reply to This

      Parent

      • Re: (Score:1)

        by DAxelrod (4649)

        Ah, true. My limited knowledge of the internals is showing. :)
      • Re: (Score:1)

        by jjore (6662)

        All rules cease to be valid as soon as an overloaded value or other unexpected get/set magic is invoked. This means I either need to guess that any operation can do anything or pretend it's not a problem and hope I get a useful answer anyway.