Skip to content

Instantly share code, notes, and snippets.

rcmlz/pre-and-postcondition.raku

Last active September 26, 2023 14:08
Show Gist options
• Save rcmlz/e4532b0c80f1ba0f47aefb30b69a0470 to your computer and use it in GitHub Desktop.
Testing pre- and post-condition directly in the signature of a function.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
 #!/usr/bin/env raku # Implementing the function # some-function$:\mathbb{Z}\times\mathbb{N} \to \{1,2,\dots,10\}, (a,b) \mapsto a + b$ where $a \equiv_2 (a+b) \equiv_2 1$ #| applied to the co-domain of &some-function() subset Allowed-Returns of UInt where * ∈ 1..10; #|« Pre- und Post-Condition in signature demonstration! * a ∈ ℤ ∧ a is odd * b ∈ ℕ ∧ (a + b) is odd * return value ∈ 1..10 » sub some-function(Int $a where * mod 2, UInt$b where { ($a +$b) mod 2 }, --> Allowed-Returns ) { $a +$b } #=« dies-ok { some-function(1+i,7) }, "(a=1+i,b=7)-> a ∉ ℤ"; dies-ok { some-function(2,7) }, "(a=2,b=7) -> a not odd"; dies-ok { some-function(3,-2) }, "(a=3,b=-2) -> b ∉ ℕ"; dies-ok { some-function(1,9) }, "(a=1,b=9) -> a+b not odd"; dies-ok { some-function(1,10) }, "(a=1,b=10) -> a+b ∉ 1..10"; nok some-function(1,6) == 9 , "(a=1,b=6) -> all pre- and post-conditions met, result incorrect"; ok some-function(1,8) == 9 , "(a=1,b=8) -> all pre- and post-conditions met, result correct"; » # run tests in trailing declarator block quick (and dirty) use Test; # ok nok is isnt is-approx is-deeply cmp-ok like unlike dies-ok etc. : https://docs.raku.org/type/Test use MONKEY-SEE-NO-EVAL; # execute an arbitrary string as Raku/Python/Perl/etc. using EVAL for &some-function.WHY.trailing.split(";") -> $single-test { EVAL$single-test }
to join this conversation on GitHub. Already have an account? Sign in to comment