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Defining, Testing and Documenting Perl?

by LanX (Archbishop)
on Dec 23, 2019 at 17:03 UTC ( #11110557=perlmeditation: print w/replies, xml ) Need Help??

Hi

I started to write a test script for "Boolean Operators" with and w/o "Short-Circuit" in Perl.

And quickly found me needing to define and test "Truthiness" in Perl.

(Wait ... "0 but true" is false? Remembered it differently ;-)

And now I find myself obliged to also define "Contexts", because an empty list is also false.

And "Data Types", because internally it's more difficult, than just Scalar, Array and Hash.

It's a lot of work, but in the end it could help in many corners when done correctly:

  • Regression testing between Perl versions
  • Leading to a proper language definition
  • Bottom up documenting the language in POD
  • Helping to test cross implementations in other languages like in JS
Properly done means that it needs to be axiomatic, i.e. higher level tests need to only use features proven in lower levels.

Like so often, after a first success I find myself a bit stuck in the big picture.

I'll throw in my first approach as is for meditation.

There is a lot to be criticized, but my normal perfectionism is too risky and might lead to a never release cycle.

Thoughts?

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

Replies are listed 'Best First'.
Re: Defining, Testing and Documenting Perl?
by Tux (Abbot) on Dec 23, 2019 at 20:37 UTC

    /me mumbles .oO( ties and overloads )


    Enjoy, Have FUN! H.Merijn

      Fun fact: the Moose "Bool" datatype will accept overloaded objects, but only if they stringify to "", "0", "1" or undef. It doesn't care what they boolify to!

      Other fun fact: the Mouse "Bool" datatype will accept overloaded objects, but only if they boolify to a false value.

       

      This is why Types::Standard 1.004 abandoned trying to be compatible with Moose and Mouse's definitions of "Bool" and instead just accepts "", "0", "1" and undef, but offers a coercion from other values.

      > mumbles .oO( ties and overloads )

      what's your point?

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

        I believe a tied hash can override how it behaves in scalar context, so that an empty hash can return true and a non-empty hash can return false.

        An overloaded object can do various tricky things with regards to how it behaves as a boolean. For example, it could die.

        if ($x || $y) { say "Something was true. What was it?"; say '$x' if $x; say '$y' if $y; } else { say "Neither was true."; }

        It is possible for this to print "Something was true?" but not tell you what was true. This is because $x or $y could be an overloaded object returning true or false at random each time they are checked.

Re: Defining, Testing and Documenting Perl?
by Anonymous Monk on Dec 24, 2019 at 20:19 UTC
    Sorry to say that not one single programming language that has "stood the tests of time" – including, by the way, JavaScript – is immune to this. Programming languages are tools of our trade which usually are developed over many decades. Shit happens – and always will. "Engineer accordingly."
      No idea what you are talking about.

      > Shit ...

      Now I smell!

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

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