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(.module:
[lux #*
[abstract
monad]
[data
[text
format]]
[macro (#+ with-gensyms)
["." code]
["s" syntax (#+ syntax:)]]])
(def: #export (assert! message test)
(-> Text Bit [])
(if test
[]
(error! message)))
(syntax: #export (pre test expr)
{#.doc (doc "Pre-conditions."
"Given a test and an expression to run, only runs the expression if the test passes."
"Otherwise, an error is raised."
(pre (i/= +4 (i/+ +2 +2))
(foo +123 +456 +789)))}
(wrap (list (` (exec (assert! (~ (code.text (format "Pre-condition failed: " (%code test))))
(~ test))
(~ expr))))))
(syntax: #export (post test expr)
{#.doc (doc "Post-conditions."
"Given a predicate and an expression to run, evaluates the expression and then tests the output with the predicate."
"If the predicate returns #1, returns the value of the expression."
"Otherwise, an error is raised."
(post i/even?
(i/+ +2 +2)))}
(with-gensyms [g!output]
(wrap (list (` (let [(~ g!output) (~ expr)]
(exec (assert! (~ (code.text (format "Post-condition failed: " (%code test))))
((~ test) (~ g!output)))
(~ g!output))))))))
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