X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=lily%2Fmusic-function.cc;h=c252291736cae35e659efc07ea6659742f2e0947;hb=97a0169312a260933246ab224e4f8b0969871dd5;hp=c485a2989c7b47738f5507931ad43153420c4b39;hpb=47db9a3883d726ca53e2133a3b2298f78dd6a32e;p=lilypond.git

diff --git a/lily/music-function.cc b/lily/music-function.cc
index c485a2989c..c252291736 100644
--- a/lily/music-function.cc
+++ b/lily/music-function.cc
@@ -18,12 +18,17 @@
 */
 
 #include "music-function.hh"
+#include "lily-parser.hh"
+#include "input.hh"
+#include "music.hh"
+#include "fluid.hh"
+#include "lily-imports.hh"
 
-const char Music_function::type_p_name_[] = "ly:music-function?";
+const char * const Music_function::type_p_name_ = "ly:music-function?";
 
 /* Print a textual represenation of the smob to a given port.  */
 int
-Music_function::print_smob (SCM port, scm_print_state *)
+Music_function::print_smob (SCM port, scm_print_state *) const
 {
   scm_puts ("#<Music function ", port);
   scm_write (get_function (), port);
@@ -33,9 +38,120 @@ Music_function::print_smob (SCM port, scm_print_state *)
   return 1;
 }
 
+// Used for attaching location information to music expressions in
+// default arguments and return values.  Music expressions taken from
+// the call signature need to be cloned since they are not suitable
+// for multiple use.
+
+static SCM
+with_loc (SCM arg, Fluid &loc, bool clone = true)
+{
+  if (Music *m = unsmob<Music> (arg))
+    {
+      if (clone)
+        {
+          m = m->clone ();
+          arg = m->unprotect ();
+        }
+      if (Input *in = unsmob<Input> (loc))
+        m->set_spot (*in);
+    }
+  return arg;
+}
+
+// A music function call implies walking through the call signature
+// and matching the actual argument list to the signature.  This
+// process is not 1:1 due to the possible presence of optional
+// arguments which are handled quite differently from how GUILE/Scheme
+// usually deal with optional arguments.
+//
+// The argument matching here intentionally closely tracks the
+// semantics of calls via the LilyPond parser as described in
+// <URL:lilypond.org/doc/Documentation/extending/scheme-function-usage>:
+// if an optional argument predicate does not match the next argument
+// from the actual argument list, the default given in the call
+// signature is used instead and all following optional arguments are
+// unconditionally substituted in a similar manner.
+//
+// This skipping of optional arguments can be explicitly initiated by
+// using \default in LilyPond.  The respective value to use for a call
+// via Scheme is *unspecified*.
+
 SCM
-Music_function::mark_smob ()
+Music_function::call (SCM rest)
 {
-  ASSERT_LIVE_IS_ALLOWED (self_scm ());
-  return Smob2<Music_function>::mark_smob ();
+  Fluid location (Lily::f_location);
+
+  // (car (ly:music-signature self_scm())) is the return type, skip it
+  SCM signature = scm_cdr (get_signature ());
+
+  // The main loop just processes the signature in sequence, and the
+  // resulting actual arguments are accumulated in reverse order in args
+
+  SCM args = SCM_EOL;
+
+  while (scm_is_pair (rest) && scm_is_pair (signature))
+    {
+      SCM arg = scm_car (rest);
+      SCM pred = scm_car (signature);
+      if (!scm_is_pair (pred))
+        {
+          // non-optional argument
+          if (scm_is_false (scm_call_1 (pred, arg)))
+            {
+              Syntax::argument_error (scm_oneplus (scm_length (args)),
+                                      pred, arg);
+              SCM val = scm_car (get_signature ());
+              val = scm_is_pair (val) ? scm_cdr (val) : SCM_BOOL_F;
+              return with_loc (val, location);
+            }
+        }
+      // If the predicate is not a function but a pair, it
+      // signifies an optional argument.  This is not quite the
+      // form declared to define-music-function (which is always
+      // a proper list) but a pair of predicate function and
+      // default value.
+      //
+      // Fall through to default argument processing when optional
+      // argument predicate matches
+      else if (scm_is_false (scm_call_1 (scm_car (pred), arg)))
+        {
+          // optional argument, non-match
+          // *unspecified* is the same as an explicit \default: skip it
+          if (scm_is_eq (arg, SCM_UNSPECIFIED))
+            rest = scm_cdr (rest);
+          // Replace this and all following optional arguments with
+          // their defaults:
+          do {
+            args = scm_cons (with_loc (scm_cdr (pred), location), args);
+            signature = scm_cdr (signature);
+            if (!scm_is_pair (signature))
+              break;
+            pred = scm_car (signature);
+          } while (scm_is_pair (pred));
+          continue;
+        }
+      // Normal processing of accepted argument
+      signature = scm_cdr (signature);
+      args = scm_cons (arg, args);
+      rest = scm_cdr (rest);
+    }
+
+  if (scm_is_pair (rest) || scm_is_pair (signature))
+    scm_wrong_num_args (self_scm ());
+
+  SCM res = scm_apply_0 (get_function (), scm_reverse_x (args, SCM_EOL));
+
+  SCM pred = scm_car (get_signature ());
+  // The return type predicate may have the form of a pair in which
+  // the car is the actual predicate and the cdr is the surrogate
+  // return value in the error case, to be extracted by
+  // music-function-call-error.
+  if (scm_is_pair (pred))
+    pred = scm_car (pred);
+
+  if (scm_is_true (scm_call_1 (pred, res)))
+    return with_loc (res, location, false);
+
+  return Syntax::music_function_call_error (self_scm (), res);
 }