Re: Make ly:make-unpure-pure-container accept a single callback (issue 7382046)

[dak]

Reviewers: MikeSol,

Message:
On 2013/02/21 19:35:35, MikeSol wrote:
> LGTM, with one suggestion: the difference between unpure and pure
functions in
> LilyPond is that unpure functions accept n arguments whereas pure
functions
> accept n+2. This shortcut you're proposing only works when n=1, which
you
> document, but it'd be nice if it worked for an arbitrary number of
input
> arguments.  It'd only be possible to do this, though, if there were a
way in C++
> to determine the number of arguments a Scheme function took.

Nonsense.  That's what the rest argument is for.  I'll submit an amended
version.

Description:
Make ly:make-unpure-pure-container accept a single callback

Like with fixed values, this gets duplicated for the pure value as
well, but converted into a three-argument callback.

Please review this at https://codereview.appspot.com/7382046/

Affected files:
  M lily/unpure-pure-container.cc


Index: lily/unpure-pure-container.cc
diff --git a/lily/unpure-pure-container.cc b/lily/unpure-pure-container.cc
index  
097cb9d80c46fc1f2baea71b6de1424a284265d9..2a762b7876ece461f164827bd75dd51c1ecdd883  
100644
--- a/lily/unpure-pure-container.cc
+++ b/lily/unpure-pure-container.cc
@@ -22,6 +22,9 @@
 #include "grob.hh"

 static scm_t_bits unpure_pure_container_tag;
+static scm_t_bits unpure_pure_call_tag;
+// Used for rerouting a function of (grob start end) to one of
+// (grob)

 bool
 is_unpure_pure_container (SCM s)
@@ -33,14 +36,21 @@ SCM
 unpure_pure_container_unpure_part (SCM smob)
 {
   LY_ASSERT_TYPE (is_unpure_pure_container, smob, 1);
-  return (SCM) SCM_CELL_WORD_1 (smob);
+  return SCM_SMOB_OBJECT (smob);
 }

 SCM
 unpure_pure_container_pure_part (SCM smob)
 {
   LY_ASSERT_TYPE (is_unpure_pure_container, smob, 1);
-  return (SCM) SCM_CELL_WORD_2 (smob);
+  SCM res = SCM_SMOB_OBJECT_2 (smob);
+
+  if (!SCM_UNBNDP (res))
+    return res;
+
+  SCM_NEWSMOB (res, unpure_pure_call_tag,
+               SCM_UNPACK (unpure_pure_container_unpure_part (smob)));
+  return res;
 }

 LY_DEFINE (ly_unpure_pure_container_p, "ly:unpure-pure-container?",
@@ -54,11 +64,13 @@ LY_DEFINE  
(ly_make_unpure_pure_container, "ly:make-unpure-pure-container",
            1, 1, 0, (SCM unpure, SCM pure),
            "Make an unpure-pure container.  @var{unpure} should be an  
unpure"
            " expression, and @var{pure} should be a pure expression.  If  
@var{pure}"
-           " is ommitted, the value of @var{unpure} will be used twice.")
+           " is omitted, the value of @var{unpure} will be used twice,"
+           " except that a callback with one argument is converted into"
+           " one with three arguments for the sake of pure calculations.")
 {
   SCM z;

-  if (pure == SCM_UNDEFINED)
+  if (SCM_UNBNDP (pure) && !ly_is_procedure (unpure))
     pure = unpure;

   SCM_NEWSMOB2 (z, unpure_pure_container_tag, SCM_UNPACK (unpure),  
SCM_UNPACK (pure));
@@ -100,11 +112,22 @@ pure_mark (SCM pure)
   return pure;
 }

+SCM
+apply_unpure_pure (SCM clo, SCM grob, SCM /* start */, SCM /* end */)
+{
+  return scm_call_1 (SCM_SMOB_OBJECT (clo), grob);
+}
+
+
 void init_unpure_pure_container ()
 {
   unpure_pure_container_tag = scm_make_smob_type ("unpure-pure-container",  
0);
   scm_set_smob_mark (unpure_pure_container_tag, pure_mark);
   scm_set_smob_print (unpure_pure_container_tag,  
print_unpure_pure_container);
+  unpure_pure_call_tag = scm_make_smob_type ("unpure-pure-call", 0);
+  scm_set_smob_mark (unpure_pure_call_tag, scm_markcdr);
+  scm_set_smob_apply (unpure_pure_call_tag,
+                      (SCM (*)()) apply_unpure_pure, 3, 0, 0);
 };

 ADD_SCM_INIT_FUNC (unpure_pure_container, init_unpure_pure_container);