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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (test-monads)
+ #:use-module (guix store)
+ #:use-module (guix monads)
+ #:use-module (guix derivations)
+ #:use-module ((guix packages)
+ #:select (package-derivation %current-system))
+ #:use-module (gnu packages)
+ #:use-module (gnu packages bootstrap)
+ #:use-module (ice-9 match)
+ #:use-module (rnrs io ports)
+ #:use-module (srfi srfi-1)
+ #:use-module (srfi srfi-26)
+ #:use-module (srfi srfi-64))
+
+;; Test the (guix store) module.
+
+(define %store
+ (open-connection))
+
+;; Make sure we build everything by ourselves.
+(set-build-options %store #:use-substitutes? #f)
+
+(define %monads
+ (list %identity-monad %store-monad))
+
+(define %monad-run
+ (list identity
+ (cut run-with-store %store <>)))
+
+
+(test-begin "monads")
+
+;; The 3 "monad laws": <http://www.haskell.org/haskellwiki/Monad_laws>.
+
+(test-assert "left identity"
+ (every (lambda (monad run)
+ (let ((number (random 777)))
+ (with-monad monad
+ (define (f x)
+ (return (* (1+ number) 2)))
+
+ (= (run (>>= (return number) f))
+ (run (f number))))))
+ %monads
+ %monad-run))
+
+(test-assert "right identity"
+ (every (lambda (monad run)
+ (with-monad monad
+ (let ((number (return (random 777))))
+ (= (run (>>= number return))
+ (run number)))))
+ %monads
+ %monad-run))
+
+(test-assert "associativity"
+ (every (lambda (monad run)
+ (with-monad monad
+ (define (f x)
+ (return (+ 1 x)))
+ (define (g x)
+ (return (* 2 x)))
+
+ (let ((number (return (random 777))))
+ (= (run (>>= (>>= number f) g))
+ (run (>>= number (lambda (x) (>>= (f x) g))))))))
+ %monads
+ %monad-run))
+
+(test-assert "lift"
+ (every (lambda (monad run)
+ (let ((f (lift1 1+ monad)))
+ (with-monad monad
+ (let ((number (random 777)))
+ (= (run (>>= (return number) f))
+ (1+ number))))))
+ %monads
+ %monad-run))
+
+(test-assert "mlet* + text-file + package-file"
+ (run-with-store %store
+ (mlet* %store-monad ((guile (package-file %bootstrap-guile "bin/guile"))
+ (file (text-file "monadic" guile)))
+ (return (equal? (call-with-input-file file get-string-all)
+ guile)))
+ #:guile-for-build (package-derivation %store %bootstrap-guile)))
+
+(test-assert "mlet* + derivation-expression"
+ (run-with-store %store
+ (mlet* %store-monad ((guile (package-file %bootstrap-guile "bin/guile"))
+ (gdrv (package->derivation %bootstrap-guile))
+ (exp -> `(let ((out (assoc-ref %outputs "out")))
+ (mkdir out)
+ (symlink ,guile
+ (string-append out "/guile-rocks"))))
+ (drv (derivation-expression "rocks" (%current-system)
+ exp `(("g" ,gdrv))))
+ (out -> (derivation->output-path drv))
+ (built? (built-derivations (list drv))))
+ (return (and built?
+ (equal? guile
+ (readlink (string-append out "/guile-rocks"))))))
+ #:guile-for-build (package-derivation %store %bootstrap-guile)))
+
+(test-assert "mapm"
+ (every (lambda (monad run)
+ (with-monad monad
+ (equal? (run (mapm monad (lift1 1+ monad) (map return (iota 10))))
+ (map 1+ (iota 10)))))
+ %monads
+ %monad-run))
+
+(test-assert "sequence"
+ (every (lambda (monad run)
+ (let* ((input (iota 100))
+ (order '()))
+ (define (frob i)
+ ;; The side effect here is used to keep track of the order in
+ ;; which monadic values are bound.
+ (set! order (cons i order))
+ i)
+
+ (and (equal? input
+ (run (sequence monad
+ (map (lift1 frob monad) input))))
+
+ ;; Make sure this is from left to right.
+ (equal? order (reverse input)))))
+ %monads
+ %monad-run))
+
+(test-assert "listm"
+ (every (lambda (monad run)
+ (run (with-monad monad
+ (let ((lst (listm monad
+ (return 1) (return 2) (return 3))))
+ (mlet monad ((lst lst))
+ (return (equal? '(1 2 3) lst)))))))
+ %monads
+ %monad-run))
+
+(test-end "monads")
+
+
+(exit (= (test-runner-fail-count (test-runner-current)) 0))