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| author | Ludovic Courtès <ludo@gnu.org> | 2022-07-10 12:39:44 +0200 |
|---|---|---|
| committer | Ludovic Courtès <ludo@gnu.org> | 2022-07-10 23:57:14 +0200 |
| commit | 9fdc4b6c283c5aa5cf10205d87fb2c58b829b9d0 (patch) | |
| tree | 9458f4783146777e11efb0de96aa6677fe5d73d0 /guix | |
| parent | bf0a646a5bcde489b602c58fbb63a93acb9d08f6 (diff) | |
monads: Add 'mparameterize'.
* etc/system-tests.scm (mparameterize): Move to...
* guix/monads.scm (mparameterize): ... here.
* tests/monads.scm ("mparameterize"): New test.
* .dir-locals.el (c-mode): Add it.
Diffstat (limited to 'guix')
| -rw-r--r-- | guix/monads.scm | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/guix/monads.scm b/guix/monads.scm index 6ae616aca9..0bd8ac9315 100644 --- a/guix/monads.scm +++ b/guix/monads.scm @@ -1,5 +1,5 @@ ;;; GNU Guix --- Functional package management for GNU -;;; Copyright © 2013, 2014, 2015, 2017 Ludovic Courtès <ludo@gnu.org> +;;; Copyright © 2013, 2014, 2015, 2017, 2022 Ludovic Courtès <ludo@gnu.org> ;;; ;;; This file is part of GNU Guix. ;;; @@ -40,6 +40,7 @@ mbegin mwhen munless + mparameterize lift0 lift1 lift2 lift3 lift4 lift5 lift6 lift7 lift listm foldm @@ -398,6 +399,21 @@ expression." (mbegin %current-monad mexp0 mexp* ...))))) +(define-syntax mparameterize + (syntax-rules () + "This form implements dynamic scoping, similar to 'parameterize', but in a +monadic context." + ((_ monad ((parameter value) rest ...) body ...) + (let ((old-value (parameter))) + (mbegin monad + ;; XXX: Non-local exits are not correctly handled. + (return (parameter value)) + (mlet monad ((result (mparameterize monad (rest ...) body ...))) + (parameter old-value) + (return result))))) + ((_ monad () body ...) + (mbegin monad body ...)))) + (define-syntax define-lift (syntax-rules () ((_ liftn (args ...)) |