Re: [PATCH 2/2] utils: Support defaults in substitute-keyword-arguments.

[Ludovic Courtès]

Eric Bavier  skribis:

> On Sat, 24 Sep 2016 11:21:40 +0900
> l...@gnu.org (Ludovic Courtès) wrote:
>> 
>> > +replaced by EXP.  EXP is evaluated in a context where VAR is bound to the
>> > +previous value of the keyword argument, or DFLT if given."
>> > +(syntax-case x ()
>> > +  ((_ original-args ((kw var dflt ...) exp) ...)
>> > +   #`(let loop ((args (default-keyword-arguments
>> > +original-args
>> > +(list #,@(append-map (match-lambda
>> > +   ((k) '())
>> > +   (x x))
>> > + #'((kw dflt ...) ...)
>> > +(before '()))  
>> 
>> I would prefer to stick to ‘syntax-rules’ when matching the clauses,
>> with a helper macro:

[...]

> From 9481121fef60f0c3f4ea0f742d77336906771167 Mon Sep 17 00:00:00 2001
> From: Eric Bavier 
> Date: Tue, 20 Sep 2016 15:41:31 -0500
> Subject: [PATCH] utils: Support defaults in substitute-keyword-arguments.
>
> * guix/utils.scm (collect-default-args, expand-default-args): New
> syntax.
> (substitute-keyword-arguments): Allow default value declarations.
> * tests/utils.scm (substitute-keyword-arguments): New test.

[...]

> +(define-syntax collect-default-args
> +  (syntax-rules ()
> +((_ (_ _))
> + (list))
> +((_ (kw _ dflt))
> + (list kw dflt))
> +((_ (_ _) rest ...)
> + (collect-default-args rest ...))
> +((_ (kw _ dflt) rest ...)
> + (cons* kw dflt (collect-default-args rest ...)

I think you just need the base case (zero args), the default-value case,
and the no-default-value case:

  (define-syntax collect-default-args
(syntax-rules ()
  ((_)   ;done
   '())
  ((_ (kw var) rest ...)
   (collect-default-args rest ...))
  ((_ (kw var dflt) rest ...)
   (cons* kw dflt (collect-default-args rest ...)

> +(define-syntax expand-default-args
> +  (syntax-rules ()
> +((_ original-args (kw var) ...)
> + original-args)
> +((_ original-args clause ...)
> + (default-keyword-arguments
> +   original-args
> +   (collect-default-args clause ...)

AFAICS this macro can be removed altogether.

OK with changes along these lines, thanks!

Ludo’.

Re: [PATCH 2/2] utils: Support defaults in substitute-keyword-arguments.

[Eric Bavier]

On Sat, 24 Sep 2016 11:21:40 +0900
l...@gnu.org (Ludovic Courtès) wrote:
> 
> > +replaced by EXP.  EXP is evaluated in a context where VAR is bound to the
> > +previous value of the keyword argument, or DFLT if given."
> > +(syntax-case x ()
> > +  ((_ original-args ((kw var dflt ...) exp) ...)
> > +   #`(let loop ((args (default-keyword-arguments
> > +original-args
> > +(list #,@(append-map (match-lambda
> > +   ((k) '())
> > +   (x x))
> > + #'((kw dflt ...) ...)
> > +(before '()))  
> 
> I would prefer to stick to ‘syntax-rules’ when matching the clauses,
> with a helper macro:

Right, I was wanting to do that, but was having a difficult time
working with mixed cases, where some keywords are declared with a
default and others are not.

> But this would be a bonus;

How about this patch instead?

`~Eric
From 9481121fef60f0c3f4ea0f742d77336906771167 Mon Sep 17 00:00:00 2001
From: Eric Bavier 
Date: Tue, 20 Sep 2016 15:41:31 -0500
Subject: [PATCH] utils: Support defaults in substitute-keyword-arguments.

* guix/utils.scm (collect-default-args, expand-default-args): New
syntax.
(substitute-keyword-arguments): Allow default value declarations.
* tests/utils.scm (substitute-keyword-arguments): New test.
---
 guix/utils.scm  | 29 +
 tests/utils.scm | 20 
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/guix/utils.scm b/guix/utils.scm
index ded3114..cbad4ea 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -375,13 +375,34 @@ keywords not already present in ARGS."
   (()
args
 
+(define-syntax collect-default-args
+  (syntax-rules ()
+((_ (_ _))
+ (list))
+((_ (kw _ dflt))
+ (list kw dflt))
+((_ (_ _) rest ...)
+ (collect-default-args rest ...))
+((_ (kw _ dflt) rest ...)
+ (cons* kw dflt (collect-default-args rest ...)
+
+(define-syntax expand-default-args
+  (syntax-rules ()
+((_ original-args (kw var) ...)
+ original-args)
+((_ original-args clause ...)
+ (default-keyword-arguments
+   original-args
+   (collect-default-args clause ...)
+
 (define-syntax substitute-keyword-arguments
   (syntax-rules ()
 "Return a new list of arguments where the value for keyword arg KW is
-replaced by EXP.  EXP is evaluated in a context where VAR is boud to the
-previous value of the keyword argument."
-((_ original-args ((kw var) exp) ...)
- (let loop ((argsoriginal-args)
+replaced by EXP.  EXP is evaluated in a context where VAR is bound to the
+previous value of the keyword argument, or DFLT if given."
+((_ original-args ((kw var dflt ...) exp) ...)
+ (let loop ((args (expand-default-args original-args
+   (kw var dflt ...) ...))
 (before '()))
(match args
  ((kw var rest (... ...))
diff --git a/tests/utils.scm b/tests/utils.scm
index 960928c..bcfaa14 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -123,6 +123,26 @@
 (default-keyword-arguments '(#:bar 3) '(#:foo 2))
 (default-keyword-arguments '(#:foo 2 #:bar 3) '(#:bar 6
 
+(test-equal "substitute-keyword-arguments"
+  '((#:foo 3)
+(#:foo 3)
+(#:foo 3 #:bar (1 2))
+(#:bar (1 2) #:foo 3)
+(#:foo 3))
+  (list (substitute-keyword-arguments '(#:foo 2)
+  ((#:foo f) (1+ f)))
+(substitute-keyword-arguments '()
+  ((#:foo f 2) (1+ f)))
+(substitute-keyword-arguments '(#:foo 2 #:bar (2))
+  ((#:foo f) (1+ f))
+  ((#:bar b) (cons 1 b)))
+(substitute-keyword-arguments '(#:foo 2)
+  ((#:foo _) 3)
+  ((#:bar b '(2)) (cons 1 b)))
+(substitute-keyword-arguments '(#:foo 2)
+  ((#:foo f 1) (1+ f))
+  ((#:bar b) (cons 42 b)
+
 (test-assert "filtered-port, file"
   (let* ((file  (search-path %load-path "guix.scm"))
  (input (open-file file "r0b")))
-- 
2.9.2

Re: [PATCH 2/2] utils: Support defaults in substitute-keyword-arguments.

[Ludovic Courtès]

Eric Bavier  skribis:

> From: Eric Bavier 
>
> * guix/utils.scm (substitute-keyword-arguments): Allow default value
> declarations.
> * tests/utils.scm (substitute-keyword-arguments): New test.

Good idea!


[...]

> +replaced by EXP.  EXP is evaluated in a context where VAR is bound to the
> +previous value of the keyword argument, or DFLT if given."
> +(syntax-case x ()
> +  ((_ original-args ((kw var dflt ...) exp) ...)
> +   #`(let loop ((args (default-keyword-arguments
> +original-args
> +(list #,@(append-map (match-lambda
> +   ((k) '())
> +   (x x))
> + #'((kw dflt ...) ...)
> +(before '()))

I would prefer to stick to ‘syntax-rules’ when matching the clauses,
with a helper macro:

  (define-syntax expand-default-args
(syntax-rules ()
  ((_ original args ((kw var) expr) rest ...)
   ...)
  ((_ original args ((kw var default) expr) rest ...)
   ...)))

  …

(syntax-rules ()
  ((_ original-args ((clause exp) ...)
   (let loop ((args (expand-default-args original-args clause ...)))
 …

But this would be a bonus; the patch LGTM.

Thanks!

Ludo’.

[PATCH 2/2] utils: Support defaults in substitute-keyword-arguments.

[Eric Bavier]

From: Eric Bavier 

* guix/utils.scm (substitute-keyword-arguments): Allow default value
declarations.
* tests/utils.scm (substitute-keyword-arguments): New test.
---
 guix/utils.scm  | 34 --
 tests/utils.scm | 20 
 2 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/guix/utils.scm b/guix/utils.scm
index ded3114..1fd6725 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -376,21 +376,27 @@ keywords not already present in ARGS."
args
 
 (define-syntax substitute-keyword-arguments
-  (syntax-rules ()
+  (lambda (x)
 "Return a new list of arguments where the value for keyword arg KW is
-replaced by EXP.  EXP is evaluated in a context where VAR is boud to the
-previous value of the keyword argument."
-((_ original-args ((kw var) exp) ...)
- (let loop ((argsoriginal-args)
-(before '()))
-   (match args
- ((kw var rest (... ...))
-  (loop rest (cons* exp kw before)))
- ...
- ((x rest (... ...))
-  (loop rest (cons x before)))
- (()
-  (reverse before)))
+replaced by EXP.  EXP is evaluated in a context where VAR is bound to the
+previous value of the keyword argument, or DFLT if given."
+(syntax-case x ()
+  ((_ original-args ((kw var dflt ...) exp) ...)
+   #`(let loop ((args (default-keyword-arguments
+original-args
+(list #,@(append-map (match-lambda
+   ((k) '())
+   (x x))
+ #'((kw dflt ...) ...)
+(before '()))
+   (match args
+ ((kw var rest (... ...))
+  (loop rest (cons* exp kw before)))
+ ...
+ ((x rest (... ...))
+  (loop rest (cons x before)))
+ (()
+  (reverse before
 
 (define (delkw kw lst)
   "Remove KW and its associated value from LST, a keyword/value list such
diff --git a/tests/utils.scm b/tests/utils.scm
index 960928c..bcfaa14 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -123,6 +123,26 @@
 (default-keyword-arguments '(#:bar 3) '(#:foo 2))
 (default-keyword-arguments '(#:foo 2 #:bar 3) '(#:bar 6
 
+(test-equal "substitute-keyword-arguments"
+  '((#:foo 3)
+(#:foo 3)
+(#:foo 3 #:bar (1 2))
+(#:bar (1 2) #:foo 3)
+(#:foo 3))
+  (list (substitute-keyword-arguments '(#:foo 2)
+  ((#:foo f) (1+ f)))
+(substitute-keyword-arguments '()
+  ((#:foo f 2) (1+ f)))
+(substitute-keyword-arguments '(#:foo 2 #:bar (2))
+  ((#:foo f) (1+ f))
+  ((#:bar b) (cons 1 b)))
+(substitute-keyword-arguments '(#:foo 2)
+  ((#:foo _) 3)
+  ((#:bar b '(2)) (cons 1 b)))
+(substitute-keyword-arguments '(#:foo 2)
+  ((#:foo f 1) (1+ f))
+  ((#:bar b) (cons 42 b)
+
 (test-assert "filtered-port, file"
   (let* ((file  (search-path %load-path "guix.scm"))
  (input (open-file file "r0b")))
-- 
2.9.3