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authorLudovic Courtès <ludo@gnu.org>2021-12-18 17:54:23 +0100
committerLudovic Courtès <ludo@gnu.org>2021-12-20 16:21:40 +0100
commitddf9345dfec208611261ab06052de47fe8873f88 (patch)
treec729962e740548bd7ca5dcfcf98ea9195b21d933
parentbdaf38a6e04052a22b62ae41c72f32cf16356314 (diff)
downloadguix-ddf9345dfec208611261ab06052de47fe8873f88.tar
guix-ddf9345dfec208611261ab06052de47fe8873f88.tar.gz
combinators: Add 'define-compile-time-procedure'.
* guix/combinators.scm (procedure-call-location): New syntax parameter. (define-compile-time-procedure): New macro.
-rw-r--r--guix/combinators.scm50
1 files changed, 48 insertions, 2 deletions
diff --git a/guix/combinators.scm b/guix/combinators.scm
index 88ad09dbe6..261d6bb57e 100644
--- a/guix/combinators.scm
+++ b/guix/combinators.scm
@@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012-2017, 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
;;; Copyright © 2020 Arun Isaac <arunisaac@systemreboot.net>
;;;
@@ -24,7 +24,9 @@
#:export (fold2
fold-tree
fold-tree-leaves
- compile-time-value))
+ compile-time-value
+ procedure-call-location
+ define-compile-time-procedure))
;;; Commentary:
;;;
@@ -100,4 +102,48 @@ evaluate to a simple datum."
(_ #`'#,(datum->syntax s val)))))))
v))))
+(define-syntax-parameter procedure-call-location
+ (lambda (s)
+ (syntax-violation 'procedure-call-location
+ "'procedure-call-location' may only be used \
+within 'define-compile-time-procedure'"
+ s)))
+
+(define-syntax-rule (define-compile-time-procedure (proc (arg pred) ...)
+ body ...)
+ "Define PROC as a macro such that, if every actual argument in a \"call\"
+matches PRED, then BODY is evaluated at macro-expansion time. BODY must
+return a single value in a type that has read syntax--e.g., numbers, strings,
+lists, etc.
+
+BODY can refer to 'procedure-call-location', which is bound to a source
+property alist corresponding to the call site.
+
+This macro is meant to be used primarily for small procedures that validate or
+process its arguments in a way that may be equally well performed at
+macro-expansion time."
+ (define-syntax proc
+ (lambda (s)
+ (define loc
+ #`(identifier-syntax
+ '#,(datum->syntax #'s (syntax-source s))))
+
+ (syntax-case s ()
+ ((_ arg ...)
+ (and (pred (syntax->datum #'arg)) ...)
+ (let ((arg (syntax->datum #'arg)) ...)
+ (syntax-parameterize ((procedure-call-location
+ (identifier-syntax (syntax-source s))))
+ body ...)))
+ ((_ actual (... ...))
+ #`((lambda (arg ...)
+ (syntax-parameterize ((procedure-call-location #,loc))
+ body ...))
+ actual (... ...)))
+ (id
+ (identifier? #'id)
+ #`(lambda (arg ...)
+ (syntax-parameterize ((procedure-call-location #,loc))
+ body ...)))))))
+
;;; combinators.scm ends here