calrissian/include/monad-tests.lfe

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(defmacro test-monad-laws (monad)
`(progn
(deftest monad-left-identity
(let ((a 3)
(f (lambda (n) (return ,monad (* 3 n)))))
(is-equal (>>= ,monad (return ,monad a) f)
(funcall f a))))
(deftest monad-right-identity
(let ((m (return ,monad 3)))
(is-equal (>>= ,monad m (lambda (m') (return ,monad m')))
m)))
(deftest monad-associativity
(let ((m (return ,monad 3))
(f (lambda (n) (return ,monad (* 3 n))))
(g (lambda (n) (return ,monad (+ 5 n)))))
(is-equal (>>= ,monad (>>= ,monad m f) g)
(>>= ,monad m (lambda (x) (>>= ,monad (funcall f x) g))))))
(deftest monad-do-left-identity
(let ((a 3)
(f (lambda (n) (return ,monad (* 3 n)))))
(is-equal (do ,monad (a' <- (return ,monad a))
(funcall f a'))
(do ,monad (funcall f a)))))
(deftest monad-do-right-identity
(let ((m (return ,monad 3)))
(is-equal (do ,monad (x <- m)
(return ,monad x))
(do ,monad m))))
(deftest monad-do-associativity
(let ((m (return ,monad 3))
(f (lambda (n) (return ,monad (* 3 n))))
(g (lambda (n) (return ,monad (+ 5 n)))))
(is-equal (do ,monad (y <- (do ,monad (x <- m)
(funcall f x)))
(funcall g y))
(do ,monad (x <- m)
(do ,monad (y <- (funcall f x))
(funcall g y))))))
))