https://github.com/shalomb/p6-assertions

Runtime assertions for Perl 6
https://github.com/shalomb/p6-assertions

assertions module perl6 perl6-module perl6-scripts

Last synced: 2 days ago
JSON representation

Runtime assertions for Perl 6

• Host: GitHub
• URL: https://github.com/shalomb/p6-assertions
• Owner: shalomb
• License: artistic-2.0
• Created: 2017-07-05T22:18:33.000Z (almost 9 years ago)
• Default Branch: master
• Last Pushed: 2017-07-06T01:59:56.000Z (almost 9 years ago)
• Last Synced: 2025-02-27T20:33:26.909Z (over 1 year ago)
• Topics: assertions, module, perl6, perl6-module, perl6-scripts
• Language: Perl6
• Size: 9.77 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

README

          
# NAME

Assertions - Runtime assertions for Perl 6

# SYNOPSIS

    use Assertions

    my $x = 42;

    assert $x;                      # Assert $x is defined and evaluates to something truthy

    assert x %% 5;                  # Assert a simple expression. `assertion failed.`

    assert $x² < 1729,              # Include a user-friendly error message

          'Ramanujan was slightly off the mark';

    assert { ($x+1).is-prime };     # Assert a block

    assert {

        ((1/$x¹, 1/$x², 1/$x³ … { $_ < 1/($x**$x) }).elems) == $x;

      },

      "No magic found with $x";

    assert { $frodo.has-ring },

           { Logger.log('Oops, he did it again!'); }

## Non-fatal assertions

In line with `assert` available in languages like C, C++, Python, etc `assert`

throws an exception if the test expression fails. To make assertions non-fatal

and log failure messages to STDERR instead, use the `:non-fatal` flag.

    my $x = (-20,-15 ... 30).pick;

    assert $x.sqrt !~~ NaN, :non-fatal;       # $x might be a negative number

    with $x { do something(); }               # control resumes here

    … 

In fact, `:non-fatal` may be needed when the test expression or block itself may

throw an (inadvertent) exception.

    assert { die  "See you later, I'm out …" },  # :non-fatal handles exceptions in this block

           { note "But wait, I live again …" },  # so that this block is called

           :non-fatal

# DESCRIPTION

`Assertions` provides an assertion mechanism for Perl 6 in the style of 

[assert.h](http://en.wikipedia.org/wiki/Assert.h) (NOTE: Unlike `assert` from 

`assert.h`, these are subroutines and are not available at compilation time).

## Note

Perl6's type system, sub/method signatures and return types, exceptions, etc

somewhat make assertions an unneeded feature of the language and you should

defer to the features of the language over the use of `assert` from this module

for performance and stability (amongst other) reasons.

# TODO

* Make use of `DEBUG` and `NDEBUG` to control assertions.

* Enable tracing to track triggered assertions.

* Consider if Smart Comments may be of use.

# SEE ALSO

* [assert.h](http://en.wikipedia.org/wiki/Assert.h) - Wikipedia page on `assert.h`

* [assertions](http://search.cpan.org/perldoc?assertions) - Assertions for Perl >= 5.9.0