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Add (guix monad-repl).

* guix/monad-repl.scm: New file.
* guix.scm: Add it.
* Makefile.am (MODULES): Add it.
* doc/guix.texi (The Store Monad): Document it.
gn-latest-20200428
Ludovic Courtès 6 years ago
parent
commit
b9b8607824
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      Makefile.am
  2. +27
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      doc/guix.texi
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  4. +81
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      guix/monad-repl.scm

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Makefile.am View File

@@ -37,6 +37,7 @@ MODULES = \
guix/download.scm \
guix/git-download.scm \
guix/monads.scm \
guix/monad-repl.scm \
guix/gexp.scm \
guix/profiles.scm \
guix/serialization.scm \


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doc/guix.texi View File

@@ -1937,6 +1937,33 @@ effect, one must use @code{run-with-store}:
@result{} /gnu/store/...-profile.sh
@end example

Note that the @code{(guix monad-repl)} module extends Guile's REPL with
new ``meta-commands'' to make it easier to deal with monadic procedures:
@code{run-in-store}, and @code{enter-store-monad}. The former, is used
to ``run'' a single monadic value through the store:

@example
scheme@@(guile-user)> ,run-in-store (package->derivation hello)
$1 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
@end example

The latter enters a recursive REPL, where all the return values are
automatically run through the store:

@example
scheme@@(guile-user)> ,enter-store-monad
store-monad@@(guile-user) [1]> (package->derivation hello)
$2 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
store-monad@@(guile-user) [1]> (text-file "foo" "Hello!")
$3 = "/gnu/store/@dots{}-foo"
store-monad@@(guile-user) [1]> ,q
scheme@@(guile-user)>
@end example

@noindent
Note that non-monadic values cannot be returned in the
@code{store-monad} REPL.

The main syntactic forms to deal with monads in general are described
below.



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guix.scm View File

@@ -30,6 +30,7 @@
ftp-client
gexp
monads
monad-repl
packages
store
utils))


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guix/monad-repl.scm View File

@@ -0,0 +1,81 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014 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 (guix monad-repl)
#:use-module (guix store)
#:use-module (guix monads)
#:use-module (ice-9 pretty-print)
#:use-module (system repl repl)
#:use-module (system repl common)
#:use-module (system repl command)
#:use-module (system base language)
#:use-module (system base compile)
#:use-module (srfi srfi-26)
#:export (run-in-store
enter-store-monad))

;;; Comment:
;;;
;;; This modules provides a couple of REPL meta-commands that make it easier
;;; to work with monadic procedures in the store monad.
;;;
;;; Code:

(define* (monad-language monad run #:optional (name 'monad))
"Return a language with a special evaluator that causes monadic values
to be \"run\" in MONAD using procedure RUN."
(let ((scheme (lookup-language 'scheme)))
(define (evaluate-monadic-expression exp env)
(let ((mvalue (compile exp #:to 'value #:env env)))
(run mvalue)))

(make-language #:name name
#:title "Monad"
#:reader (language-reader scheme)
#:compilers (language-compilers scheme)
#:decompilers (language-decompilers scheme)
#:evaluator evaluate-monadic-expression
#:printer (language-printer scheme)
#:make-default-environment
(language-make-default-environment scheme))))

(define (store-monad-language)
"Return a compiler language for the store monad."
(let ((store (open-connection)))
(monad-language %store-monad
(cut run-with-store store <>)
'store-monad)))

(define-meta-command ((run-in-store guix) repl (form))
"run-in-store EXP
Run EXP through the store monad."
(let ((value (with-store store
(run-with-store store (repl-eval repl form)))))
(run-hook before-print-hook value)
(pretty-print value)))

(define-meta-command ((enter-store-monad guix) repl)
"enter-store-monad
Enter a REPL for values in the store monad."
(let ((new (make-repl (store-monad-language))))
;; Force interpretation so that our specially-crafted language evaluator
;; is actually used.
(repl-option-set! new 'interp #t)
(run-repl new)))

;;; monad-repl.scm ends here

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