From: "Ludovic Courtès" <ludo@gnu.org>
To: 29296@debbugs.gnu.org
Subject: [bug#29296] [PATCH 1/2] gexp: Compilers can now return lowerable objects.
Date: Tue, 14 Nov 2017 17:25:14 +0100 [thread overview]
Message-ID: <20171114162515.8743-1-ludo@gnu.org> (raw)
In-Reply-To: <20171114161841.8485-1-ludo@gnu.org>
* guix/gexp.scm (lower-object): Iterate if LOWERED is a struct.
(lower+expand-object): New procedure.
(gexp->sexp): Use it.
(define-gexp-compiler): Adjust docstring.
---
guix/gexp.scm | 54 +++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 39 insertions(+), 15 deletions(-)
diff --git a/guix/gexp.scm b/guix/gexp.scm
index b9525603e..c2d942c7f 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -195,24 +195,50 @@ procedure to expand it; otherwise return #f."
corresponding to OBJ for SYSTEM, cross-compiling for TARGET if TARGET is true.
OBJ must be an object that has an associated gexp compiler, such as a
<package>."
- (match (lookup-compiler obj)
- (#f
- (raise (condition (&gexp-input-error (input obj)))))
- (lower
- (lower obj system target))))
+ (let loop ((obj obj))
+ (match (lookup-compiler obj)
+ (#f
+ (raise (condition (&gexp-input-error (input obj)))))
+ (lower
+ (mlet %store-monad ((lowered (lower obj system target)))
+ (if (and (struct? lowered) (not (eq? lowered obj)))
+ (loop lowered)
+ (return lowered)))))))
+
+(define* (lower+expand-object obj
+ #:optional (system (%current-system))
+ #:key target (output "out"))
+ "Return as a value in %STORE-MONAD the output of object OBJ expands to for
+SYSTEM and TARGET. Object such as <package>, <file-append>, or <plain-file>
+expand to file names, but it's possible to expand to a plain data type."
+ (let loop ((obj obj)
+ (expand (and (struct? obj) (lookup-expander obj))))
+ (match (lookup-compiler obj)
+ (#f
+ (raise (condition (&gexp-input-error (input obj)))))
+ (lower
+ (mlet %store-monad ((lowered (lower obj system target)))
+ ;; LOWER might return something that needs to be further lowered.
+ (if (struct? lowered)
+ ;; If we lack an expander, delegate to that of LOWERED.
+ (if (not expand)
+ (loop lowered (lookup-expander lowered))
+ (return (expand obj lowered output)))
+ (return lowered))))))) ;lists, vectors, etc.
(define-syntax define-gexp-compiler
(syntax-rules (=> compiler expander)
"Define NAME as a compiler for objects matching PREDICATE encountered in
gexps.
-In the simplest form of the macro, BODY must return a derivation for PARAM, an
-object that matches PREDICATE, for SYSTEM and TARGET (the latter of which is
-#f except when cross-compiling.)
+In the simplest form of the macro, BODY must return (1) a derivation for
+a record of the specified type, for SYSTEM and TARGET (the latter of which is
+#f except when cross-compiling), (2) another record that can itself be
+compiled down to a derivation, or (3) an object of a primitive data type.
The more elaborate form allows you to specify an expander:
- (define-gexp-compiler something something?
+ (define-gexp-compiler something-compiler <something>
compiler => (lambda (param system target) ...)
expander => (lambda (param drv output) ...))
@@ -795,12 +821,10 @@ and in the current monad setting (system type, etc.)"
(or n? native?)))
refs)))
(($ <gexp-input> (? struct? thing) output n?)
- (let ((target (if (or n? native?) #f target))
- (expand (lookup-expander thing)))
- (mlet %store-monad ((obj (lower-object thing system
- #:target target)))
- ;; OBJ must be either a derivation or a store file name.
- (return (expand thing obj output)))))
+ (let ((target (if (or n? native?) #f target)))
+ (lower+expand-object thing system
+ #:target target
+ #:output output)))
(($ <gexp-input> x)
(return x))
(x
--
2.15.0
next prev parent reply other threads:[~2017-11-14 16:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-14 16:18 [bug#29296] [PATCH 0/2] gexp: Add 'let-system' Ludovic Courtès
2017-11-14 16:25 ` Ludovic Courtès [this message]
2017-11-14 16:25 ` [bug#29296] [PATCH 2/2] " Ludovic Courtès
2017-11-15 11:27 ` Mathieu Othacehe
2017-11-16 9:10 ` Ludovic Courtès
2020-05-22 22:44 ` Danny Milosavljevic
2020-05-22 23:01 ` Marius Bakke
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