From 1fcdbd59e06f27b6489f8efa2afdebf7e99b3366 Mon Sep 17 00:00:00 2001
From: hanwen <hanwen>
Date: Sun, 18 Jan 2004 20:28:51 +0000
Subject: [PATCH] * lily/lily-guile.cc (robust_scm2double): new function. Use
 throughout.

* lily/hairpin.cc: use Line_interface

* lily/tuplet-bracket.cc (make_bracket): use Line_interface.

* lily/mensural-ligature.cc (brew_flexa): replace horizontal_slope
() with beam ().

* lily/beam.cc (position_beam): new function
(brew_molecule): make sure that positions are calced before making
the molecule.

* lily/beam.cc (brew_molecule): fix beam offsets: overlap with the
stem do avoid small dents.
---
 ChangeLog                               |  2 +
 lily/accidental-placement.cc            | 16 +++-----
 lily/align-interface.cc                 | 17 +-------
 lily/balloon.cc                         |  7 +---
 lily/bar-line.cc                        | 10 ++---
 lily/beam.cc                            | 20 ++++------
 lily/breathing-sign.cc                  |  4 ++
 lily/cluster.cc                         |  8 +---
 lily/dynamic-performer.cc               | 10 ++---
 lily/font-select.cc                     |  3 +-
 lily/grob.cc                            | 14 +++----
 lily/hairpin.cc                         |  2 +-
 lily/hyphen-spanner.cc                  |  8 ++--
 lily/include/lily-guile.hh              |  3 +-
 lily/lily-guile.cc                      | 13 ++++++-
 lily/line-spanner.cc                    |  9 ++---
 lily/lyric-extender.cc                  |  4 +-
 lily/measure-grouping-spanner.cc        |  8 +++-
 lily/mensural-ligature-engraver.cc      |  8 +---
 lily/mensural-ligature.cc               | 13 +------
 lily/multi-measure-rest.cc              |  8 ++--
 lily/note-head.cc                       |  2 +-
 lily/note-spacing.cc                    |  8 ++--
 lily/percent-repeat-item.cc             |  4 +-
 lily/separation-item.cc                 | 12 +-----
 lily/side-position-interface.cc         | 12 +-----
 lily/slur.cc                            | 10 ++---
 lily/spacing-spanner.cc                 | 16 ++++----
 lily/spanner.cc                         |  2 +-
 lily/staff-spacing.cc                   |  4 +-
 lily/staff-symbol-referencer.cc         | 10 +----
 lily/staff-symbol.cc                    | 11 +-----
 lily/stem-tremolo.cc                    |  4 +-
 lily/stem.cc                            | 19 ++++-----
 lily/system-start-delimiter-engraver.cc |  2 +-
 lily/system-start-delimiter.cc          |  5 +--
 lily/text-spanner.cc                    |  7 +---
 lily/tie.cc                             |  2 +-
 lily/tuplet-bracket.cc                  |  4 +-
 lily/vaticana-ligature-engraver.cc      | 28 +------------
 lily/vaticana-ligature.cc               | 52 ++-----------------------
 lily/volta-bracket.cc                   |  2 +-
 42 files changed, 128 insertions(+), 275 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 978247bfd5..df9602dfc7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2004-01-18  Han-Wen Nienhuys   <hanwen@xs4all.nl>
 
+	* lily/lily-guile.cc (robust_scm2double): new function. Use throughout.
+
 	* lily/line-interface.cc (line): remove thickness from calling interface.
 
 	* lily/hairpin.cc: use Line_interface
diff --git a/lily/accidental-placement.cc b/lily/accidental-placement.cc
index 46c765daf2..bfe0f1b58a 100644
--- a/lily/accidental-placement.cc
+++ b/lily/accidental-placement.cc
@@ -121,7 +121,7 @@ Accidental_placement::get_relevant_accidental_extent (Grob *me,
 
   if (!extent.is_empty ())
     {
-      Real p = gh_scm2double (me->get_grob_property ("left-padding"));
+      Real p = robust_scm2double (me->get_grob_property ("left-padding"), 0.2);
       extent[LEFT] -= p;
     }
   
@@ -380,15 +380,10 @@ Accidental_placement::position_accidentals (Grob * me)
   head_ape-> left_skyline_ = head_skyline;
   head_ape->offset_ = 0.0;
 
-  SCM rs = me->get_grob_property ("right-padding");
-  if (gh_number_p (rs))
-    head_ape->offset_ -= gh_scm2double (rs);
+  head_ape->offset_ -= robust_scm2double ( me->get_grob_property ("right-padding"), 0);
 
   
-  Real padding = 0.2;
-  SCM spad = me->get_grob_property ("padding");
-  if (gh_number_p (spad))
-    padding = gh_scm2double (spad);
+  Real padding = robust_scm2double (me->get_grob_property ("padding"),0.2);
 
   Array<Skyline_entry> left_skyline = head_ape->left_skyline_;
   /*
@@ -431,9 +426,8 @@ Accidental_placement::position_accidentals (Grob * me)
   for (int i = ape->extents_.size(); i--;)
     right_extent.unite (ape->offset_  + ape->extents_[i][X_AXIS]);
 
-  SCM ls = me->get_grob_property ("left-padding");
-  if (gh_number_p (rs))
-    left_extent[LEFT] -= gh_scm2double (ls);
+  
+  left_extent[LEFT] -= robust_scm2double (me->get_grob_property ("left-padding"), 0);
 
   
   Interval width(left_extent[LEFT], right_extent[RIGHT]);
diff --git a/lily/align-interface.cc b/lily/align-interface.cc
index 3b020ea677..62865dc949 100644
--- a/lily/align-interface.cc
+++ b/lily/align-interface.cc
@@ -56,13 +56,7 @@ Align_interface::align_to_fixed_distance (Grob *me , Axis a)
   if (!stacking_dir)
     stacking_dir = DOWN;
 
-  SCM force = me->get_grob_property ("forced-distance");
-
-  Real dy = 0.0;
-  if (gh_number_p (force))
-    {
-      dy = gh_scm2double (force);
-    }
+  Real dy = robust_scm2double (me->get_grob_property ("forced-distance"),0.0);
   
   Link_array<Grob> elems
     = Pointer_group_interface__extract_grobs (me, (Grob*) 0, "elements");
@@ -134,14 +128,7 @@ Align_interface::align_elements_to_extents (Grob * me, Axis a)
   if (!stacking_dir)
     stacking_dir = DOWN;
   
-  Interval threshold = Interval (0, Interval::infinity ());
-  SCM thr = me->get_grob_property ("threshold");
-  if (gh_pair_p (thr))
-    {
-      threshold[SMALLER] = gh_scm2double (ly_car (thr));
-      threshold[BIGGER] = gh_scm2double (ly_cdr (thr));      
-    }
-
+  Interval threshold  = robust_scm2interval ( me->get_grob_property ("threshold"), Interval (0, Interval::infinity ()));
   
   Array<Interval> dims;
 
diff --git a/lily/balloon.cc b/lily/balloon.cc
index 78938c9914..30eb59e7c0 100644
--- a/lily/balloon.cc
+++ b/lily/balloon.cc
@@ -47,12 +47,7 @@ Balloon_interface::brew_molecule (SCM smob)
   Box orig_extent = m->extent_box ();
   Box box_extent = orig_extent;
 
-  SCM widen = me->get_grob_property ("balloon-padding");
-  Real w = .1;
-  if (gh_number_p (widen))
-    {
-      w = gh_scm2double (widen);
-    }
+  Real w = robust_scm2double (me->get_grob_property ("balloon-padding"),  .1);
   box_extent.widen (w, w);
   
   
diff --git a/lily/bar-line.cc b/lily/bar-line.cc
index d729f83429..b27ba0b92a 100644
--- a/lily/bar-line.cc
+++ b/lily/bar-line.cc
@@ -34,7 +34,7 @@ Bar_line::brew_molecule (SCM smob)
     {
       String str  =ly_scm2string (s);
       SCM siz = gh_call1 (barsiz_proc, me->self_scm ());
-      Real sz =  gh_scm2double (siz);
+      Real sz = robust_scm2double (siz, 0);
       if (sz < 0)
 	return SCM_EOL;
       
@@ -47,10 +47,10 @@ Bar_line::brew_molecule (SCM smob)
 Molecule
 Bar_line::compound_barline (Grob*me, String str, Real h)
 {
-  Real kern = gh_scm2double (me->get_grob_property ("kern"));
-  Real thinkern = gh_scm2double (me->get_grob_property ("thin-kern"));
-  Real hair = gh_scm2double (me->get_grob_property ("hair-thickness"));
-  Real fatline = gh_scm2double (me->get_grob_property ("thick-thickness"));
+  Real kern = robust_scm2double (me->get_grob_property ("kern"), 1);
+  Real thinkern = robust_scm2double (me->get_grob_property ("thin-kern"), 1);
+  Real hair = robust_scm2double (me->get_grob_property ("hair-thickness"), 1);
+  Real fatline = robust_scm2double (me->get_grob_property ("thick-thickness"), 1);
 
   Real staffline = me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
   Real staff_space = Staff_symbol_referencer::staff_space (me);
diff --git a/lily/beam.cc b/lily/beam.cc
index e049696eb8..c000147a33 100644
--- a/lily/beam.cc
+++ b/lily/beam.cc
@@ -71,11 +71,8 @@ Beam::add_stem (Grob *me, Grob *s)
 Real
 Beam::get_thickness (Grob * me)
 {
-  SCM th = me->get_grob_property ("thickness");
-  if (gh_number_p (th))
-    return gh_scm2double (th)* Staff_symbol_referencer::staff_space (me);
-  else
-    return 0.0;
+  return robust_scm2double (me->get_grob_property ("thickness"), 0)
+    * Staff_symbol_referencer::staff_space (me);
 }
 
 /* Return the translation between 2 adjoining beams. */
@@ -339,10 +336,7 @@ Beam::brew_molecule (SCM grob)
   Real last_xposn = -1;
   Real last_stem_width = -1 ;
 
-  Real gap_length =0.0;
-  SCM scm_gap = me->get_grob_property ("gap");
-  if (gh_number_p (scm_gap))
-    gap_length = gh_scm2double (scm_gap);
+  Real gap_length =robust_scm2double ( me->get_grob_property ("gap"), 0.0);
   
   Molecule the_beam;
   Real lt = me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
@@ -353,7 +347,7 @@ Beam::brew_molecule (SCM grob)
       
       SCM this_beaming = st ? st->get_grob_property ("beaming") : SCM_EOL;
       Real xposn = st ? st->relative_coordinate (xcommon, X_AXIS) : 0.0;
-      Real stem_width = st ? gh_scm2double (st->get_grob_property ("thickness")) *lt : 0 ;
+      Real stem_width = st ? robust_scm2double (st->get_grob_property ("thickness"), 1.0) *lt : 0 ;
       Direction stem_dir = st ? to_dir (st->get_grob_property ("direction")) : CENTER;
       /*
 	We do the space left of ST, with lfliebertjes pointing to the
@@ -882,7 +876,7 @@ Beam::least_squares (SCM smob)
 	{
 	  /* FIXME. -> UP */
 	  Direction d = (Direction) (sign (chord.delta ()) * UP);
-	  pos[d] = gh_scm2double (me->get_grob_property ("thickness")) / 2;
+	  pos[d] = get_thickness (me) / 2;
 	  pos[-d] = - pos[d];
 	}
       else
@@ -1480,8 +1474,8 @@ Beam::rest_collision_callback (SCM element_smob, SCM axis)
   Grob *common_x = rest->common_refpoint (beam, Y_AXIS);
   Real rest_dim = rest->extent (common_x, Y_AXIS)[d] / staff_space * d;
 
-  Real minimum_distance = gh_scm2double
-    (rest->get_grob_property ("minimum-beam-collision-distance"));
+  Real minimum_distance = robust_scm2double
+    (rest->get_grob_property ("minimum-beam-collision-distance"), 1);
 
   Real distance = beam_y - rest_dim;
   Real shift = 0;
diff --git a/lily/breathing-sign.cc b/lily/breathing-sign.cc
index ede4b2f8b9..006682be8a 100644
--- a/lily/breathing-sign.cc
+++ b/lily/breathing-sign.cc
@@ -30,6 +30,10 @@
 
   
 
+/*
+  UGH : this is full of C&P code. Consolidate!  --hwn
+*/
+
 /*
   Gregorian chant divisio minima.  (Actually, this was the original
   breathing sign by Michael. -- jr)
diff --git a/lily/cluster.cc b/lily/cluster.cc
index c89b752fbe..9c1bf995fb 100644
--- a/lily/cluster.cc
+++ b/lily/cluster.cc
@@ -32,12 +32,8 @@ brew_cluster_piece (Grob *me, Array<Offset> bottom_points, Array<Offset> top_poi
 {
   Real blotdiameter = Staff_symbol_referencer::staff_space (me)/2;
 
-  Real padding;
-  SCM padding_scm = me->get_grob_property ("padding");
-  if (gh_number_p (padding_scm))
-    padding = gh_scm2double (padding_scm);
-  else
-    padding = 0.0;
+  Real padding =robust_scm2double ( me->get_grob_property ("padding"), 0.0);
+
   Offset vpadding = Offset (0, padding);
   Offset hpadding = Offset (0.5 * blotdiameter, 0);
   Offset hvpadding = 0.5 * hpadding + vpadding;
diff --git a/lily/dynamic-performer.cc b/lily/dynamic-performer.cc
index aefb86da9c..c0df3e0cae 100644
--- a/lily/dynamic-performer.cc
+++ b/lily/dynamic-performer.cc
@@ -52,9 +52,7 @@ Dynamic_performer::create_audio_elements ()
 	  svolume = gh_call1 (proc, script_req_->get_mus_property ("text"));
 	}
 
-      Real volume = 0.5; 
-      if (gh_number_p (svolume))
-	volume = gh_scm2double (svolume);
+      Real volume = robust_scm2double (svolume, 0.5); 
 
       /*
 	properties override default equaliser setting
@@ -90,11 +88,9 @@ Dynamic_performer::create_audio_elements ()
 	      s = gh_call1 (eq, s);
 	    }
 
-	  if (gh_pair_p (s))
+	  if (is_number_pair (s))
 	    {
-	      Interval iv;
-	      iv[MIN] = gh_scm2double (ly_car (s));
-	      iv[MAX] = gh_scm2double (ly_cdr (s));
+	      Interval iv = ly_scm2interval (s);
 	      volume = iv[MIN] + iv.length () * volume;
 	    }
 	}
diff --git a/lily/font-select.cc b/lily/font-select.cc
index 294ba8d3fc..61ae2fa4fc 100644
--- a/lily/font-select.cc
+++ b/lily/font-select.cc
@@ -153,8 +153,7 @@ select_font (Paper_def *paper, SCM chain)
     {
       SCM mag = ly_assoc_chain (ly_symbol2scm ("font-magnification"), chain);
   
-      Real rmag = gh_pair_p (mag) && gh_number_p (gh_cdr (mag))
-	? gh_scm2double (gh_cdr (mag)) : 1.0;
+      Real rmag = gh_pair_p (mag) ? robust_scm2double (gh_cdr (mag), 1.0) : 1;
   
       return paper->find_font (name, rmag);
     }
diff --git a/lily/grob.cc b/lily/grob.cc
index b11c5b6915..0e82fef490 100644
--- a/lily/grob.cc
+++ b/lily/grob.cc
@@ -177,15 +177,11 @@ Grob::preset_extent (SCM element_smob, SCM scm_axis)
   SCM ext = s->get_grob_property ((a == X_AXIS)
 				 ? "X-extent"
 				 : "Y-extent");
-  
-  if (gh_pair_p (ext))
-    {
-      Real l = gh_scm2double (ly_car (ext));
-      Real r = gh_scm2double (ly_cdr (ext));
-      return ly_interval2scm (Interval (l, r));
-    }
-  
-  return ly_interval2scm (Interval ());
+
+  if (is_number_pair (ext))
+    return ext;
+  else
+    return ly_interval2scm (Interval());
 }
 
 
diff --git a/lily/hairpin.cc b/lily/hairpin.cc
index 66a9931df8..41e9eef5ef 100644
--- a/lily/hairpin.cc
+++ b/lily/hairpin.cc
@@ -100,7 +100,7 @@ Hairpin::brew_molecule (SCM smob)
     }
 
   bool continued = broken[Direction (-grow_dir)];
-  Real height = gh_scm2double (me->get_grob_property ("height"));
+  Real height = robust_scm2double (me->get_grob_property ("height"), 0.2);
 
   Real starth, endh;
   if (grow_dir < 0)
diff --git a/lily/hyphen-spanner.cc b/lily/hyphen-spanner.cc
index 8334e494cc..17b01dad53 100644
--- a/lily/hyphen-spanner.cc
+++ b/lily/hyphen-spanner.cc
@@ -43,13 +43,13 @@ Hyphen_spanner::brew_molecule (SCM smob)
   while (flip (&d) != LEFT);
   
   Real lt = sp->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
-  Real th = gh_scm2double (sp->get_grob_property ("thickness")) * lt ;
-  Real h = gh_scm2double (sp->get_grob_property ("height"));
+  Real th = robust_scm2double (sp->get_grob_property ("thickness"), 1) * lt ;
+  Real h = robust_scm2double (sp->get_grob_property ("height"), 0.5);
 
   // interval?
   
-  Real dp = gh_scm2double (sp->get_grob_property ("dash-period"));
-  Real dl = gh_scm2double (sp->get_grob_property ("length"));
+  Real dp = robust_scm2double (sp->get_grob_property ("dash-period"), 1.0);
+  Real dl = robust_scm2double (sp->get_grob_property ("length"), .5 );
 
   if (dp < dl)
     dp = 1.5 * dl;
diff --git a/lily/include/lily-guile.hh b/lily/include/lily-guile.hh
index 613099e24e..19fed5950a 100644
--- a/lily/include/lily-guile.hh
+++ b/lily/include/lily-guile.hh
@@ -160,7 +160,8 @@ Slice int_list_to_slice (SCM l);
 SCM ly_interval2scm (Drul_array<Real>);
 
 Real robust_scm2double (SCM, double);
-Drul_array<Real> robust_scm2interval (SCM, Drul_array<Real>);
+Drul_array<Real> robust_scm2drul (SCM, Drul_array<Real>);
+Interval robust_scm2interval (SCM, Drul_array<Real>);
 Offset robust_scm2offset (SCM, Offset);
 
 SCM ly_quote_scm (SCM s);
diff --git a/lily/lily-guile.cc b/lily/lily-guile.cc
index c7641e7447..559aec578f 100644
--- a/lily/lily-guile.cc
+++ b/lily/lily-guile.cc
@@ -724,8 +724,19 @@ robust_scm2double (SCM k, double x)
   return x;
 }
 
-Drul_array<Real>
+Interval
 robust_scm2interval (SCM k, Drul_array<Real> v)
+{
+  Interval i;
+  i[LEFT]= v[LEFT];
+  i[RIGHT]= v[RIGHT];
+  if (is_number_pair (k))
+    i = ly_scm2interval (k);
+  return i;
+}
+
+Drul_array<Real>
+robust_scm2drul (SCM k, Drul_array<Real> v)
 {
   if (is_number_pair (k))
     v = ly_scm2interval (k);
diff --git a/lily/line-spanner.cc b/lily/line-spanner.cc
index 578206975d..3b74fb1497 100644
--- a/lily/line-spanner.cc
+++ b/lily/line-spanner.cc
@@ -34,10 +34,9 @@ zigzag_molecule (Grob *me,
   thick *= robust_scm2double (me->get_grob_property ("thickness"), 1.0); // todo: staff sym referencer? 
   
   Real staff_space = Staff_symbol_referencer::staff_space (me);
-  SCM ws = me->get_grob_property ("zigzag-width");
-  SCM ls = me->get_grob_property ("zigzag-length");
-  double w = (gh_number_p(ws) ? gh_scm2double(ws) : 1)*staff_space;
-  double l = (gh_number_p(ls) ? gh_scm2double(ls) : 1)*w;
+
+  double w = robust_scm2double (me->get_grob_property ("zigzag-width"), 1)*staff_space;
+  double l = robust_scm2double ( me->get_grob_property ("zigzag-length"), 1)* w;
   double h = l>w/2 ? sqrt(l*l-w*w/4) : 0;
   
   SCM list = scm_list_n (ly_symbol2scm ("zigzag-line"),
@@ -183,7 +182,7 @@ Line_spanner::brew_molecule (SCM smob)
 			    me->get_bound (RIGHT));
   
   
-  Real gap = gh_scm2double (me->get_grob_property ("gap"));
+  Real gap = robust_scm2double (me->get_grob_property ("gap"), 0.0);
 
   Offset ofxy (gap, 0); /*offset from start point to start of line*/
   Offset dxy ;
diff --git a/lily/lyric-extender.cc b/lily/lyric-extender.cc
index 25cfb2bd1e..73a1d49119 100644
--- a/lily/lyric-extender.cc
+++ b/lily/lyric-extender.cc
@@ -54,14 +54,14 @@ Lyric_extender::brew_molecule (SCM smob)
    */
   SCM minlen =  me->get_grob_property ("minimum-length");
   Real right_point
-    = left_point + (gh_number_p (minlen) ? gh_scm2double (minlen) : 0.0);
+    = left_point + (robust_scm2double  (minlen,0));
 
   if (r->break_status_dir ())
     right_point = infinity_f;
   else
     right_point = right_point >? heads.top ()->extent (common, X_AXIS)[RIGHT];
   
-  Real h = sl * gh_scm2double (me->get_grob_property ("thickness"));
+  Real h = sl * robust_scm2double (me->get_grob_property ("thickness"), 0);
   Real pad = 2* h;
   right_point = right_point <? (r->extent (common, X_AXIS)[LEFT] - pad);
 
diff --git a/lily/measure-grouping-spanner.cc b/lily/measure-grouping-spanner.cc
index df06b7f30a..9af72c3405 100644
--- a/lily/measure-grouping-spanner.cc
+++ b/lily/measure-grouping-spanner.cc
@@ -25,7 +25,7 @@ Measure_grouping::brew_molecule (SCM grob)
   SCM thick = me->get_grob_property ("thickness");
   SCM height = me->get_grob_property ("height");
 
-  Real t = me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness")) *   gh_scm2double (thick); 
+  Real t = me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness")) * gh_scm2double (thick); 
   Grob *common = me->get_bound(LEFT)->common_refpoint (me->get_bound (RIGHT),
 						       X_AXIS);
 
@@ -39,7 +39,11 @@ Measure_grouping::brew_molecule (SCM grob)
 
   Interval iv (0,w);
 
-  Molecule m; 
+  Molecule m;
+
+  /*
+    TODO: use line interface
+   */
   if (which == ly_symbol2scm ("bracket"))
     {
       m = Lookup::bracket (X_AXIS, iv, t,-gh_scm2double (height), t);
diff --git a/lily/mensural-ligature-engraver.cc b/lily/mensural-ligature-engraver.cc
index f8786b4314..cd08766d56 100644
--- a/lily/mensural-ligature-engraver.cc
+++ b/lily/mensural-ligature-engraver.cc
@@ -343,17 +343,13 @@ void
 Mensural_ligature_engraver::propagate_properties (Spanner *ligature,
 						  Array<Grob_info> primitives)
 {
-  SCM thickness_scm = ligature->get_grob_property ("thickness");
-  Real thickness = (thickness_scm != SCM_EOL) ?
-    gh_scm2double (thickness_scm) : 1.4;
+  Real thickness = robust_scm2double (ligature->get_grob_property ("thickness"), 1.4);
   thickness *= ligature->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
 
   Real head_width =
     Font_interface::get_default_font (ligature)->
     find_by_name ("noteheads--1mensural").extent (X_AXIS).length ();
-  SCM flexa_width_scm = ligature->get_grob_property ("flexa-width");
-  Real flexa_width = (flexa_width_scm != SCM_EOL) ?
-    gh_scm2double (flexa_width_scm) : 2.0;
+    Real flexa_width = robust_scm2double (ligature->get_grob_property ("flexa-width"), 2);
   flexa_width *= Staff_symbol_referencer::staff_space (ligature);
 
   Real half_flexa_width = 0.5 * (flexa_width + thickness);
diff --git a/lily/mensural-ligature.cc b/lily/mensural-ligature.cc
index c0bb7fac49..e8df8353a7 100644
--- a/lily/mensural-ligature.cc
+++ b/lily/mensural-ligature.cc
@@ -172,18 +172,7 @@ internal_brew_primitive (Grob *me, bool ledger_take_space)
 	  delta_pitch = 0;
 	}
 
-      SCM flexa_width_scm = me->get_grob_property ("flexa-width");
-      if (flexa_width_scm != SCM_EOL)
-	{
-	  flexa_width = gh_scm2double (flexa_width_scm);
-	}
-      else
-	{
-	  programming_error (_f ("Mensural_ligature:"
-				 "flexa-width undefined on flexa %d; assuming 2.0",
-				 primitive));
-	  flexa_width = 2.0 * staff_space;
-	}
+      flexa_width = robust_scm2double (me->get_grob_property ("flexa-width"), 2.0 * staff_space);
     }
 
   switch (primitive)
diff --git a/lily/multi-measure-rest.cc b/lily/multi-measure-rest.cc
index e6e747e23c..f0522329b0 100644
--- a/lily/multi-measure-rest.cc
+++ b/lily/multi-measure-rest.cc
@@ -180,8 +180,8 @@ Multi_measure_rest::symbol_molecule (Grob *me, Real space)
 Molecule
 Multi_measure_rest::big_rest (Grob *me, Real width)
 {
-  Real thick_thick = gh_scm2double (me->get_grob_property ("thick-thickness"));
-  Real hair_thick = gh_scm2double (me->get_grob_property ("hair-thickness"));
+  Real thick_thick =robust_scm2double (me->get_grob_property ("thick-thickness"), 1.0);
+  Real hair_thick = robust_scm2double (me->get_grob_property ("hair-thickness"), .1);
 
 
   Real ss = Staff_symbol_referencer::staff_space (me);
@@ -337,9 +337,7 @@ Multi_measure_rest::set_spacing_rods (SCM smob)
       rod.distance_ = l->extent (l, X_AXIS)[BIGGER] - r->extent (r, X_AXIS)[SMALLER]
 	+ sym_width  + 2.0;			// 2.0 = magic!
   
-      Real minlen  =0.0;
-      SCM ml  =me->get_grob_property ("minimum-length");
-      if (gh_number_p (ml)) minlen = gh_scm2double (ml);
+      Real minlen  = robust_scm2double (me->get_grob_property ("minimum-length"), 0.0);
       rod.distance_ = max(rod.distance_,
 			  minlen);
       rod.add_to_cols ();
diff --git a/lily/note-head.cc b/lily/note-head.cc
index bce006a920..5942c1dc6d 100644
--- a/lily/note-head.cc
+++ b/lily/note-head.cc
@@ -303,7 +303,7 @@ Note_head::stem_attachment_coordinate (Grob *me, Axis a)
 
   result = (a == X_AXIS) ? ly_car (result) : ly_cdr (result);
   
-  return gh_number_p (result) ?  gh_scm2double (result) : 0.0;
+  return robust_scm2double (result,0);
 }
 
 int
diff --git a/lily/note-spacing.cc b/lily/note-spacing.cc
index 38c8438872..0cf786d751 100644
--- a/lily/note-spacing.cc
+++ b/lily/note-spacing.cc
@@ -355,7 +355,7 @@ Note_spacing::stem_dir_correction (Grob*me, Item * rcolumn,
 
 	      if (st)
 		{
-		  Real thick = gh_scm2double (st->get_grob_property ("thickness"))
+		  Real thick = robust_scm2double (st->get_grob_property ("thickness"), 1)
 		    * st->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
 
 		  note_head_width -= thick;
@@ -363,7 +363,7 @@ Note_spacing::stem_dir_correction (Grob*me, Item * rcolumn,
 	    }
 
 	  correction = note_head_width* stem_dirs[LEFT];
-	  correction *= gh_scm2double (me->get_grob_property ("knee-spacing-correction"));
+	  correction *= robust_scm2double (me->get_grob_property ("knee-spacing-correction"), 0);
 	  *fixed += correction;
 	}
       else
@@ -383,7 +383,7 @@ Note_spacing::stem_dir_correction (Grob*me, Item * rcolumn,
 	      correction = (correction/7) <? 1.0;
 	      correction *= stem_dirs[LEFT] ;
 	      correction *=
-		gh_scm2double (me->get_grob_property ("stem-spacing-correction"));
+		robust_scm2double (me->get_grob_property ("stem-spacing-correction"), 0);
 	    }
 	  
 	  if (!bar_yextent.is_empty ())
@@ -423,7 +423,7 @@ Note_spacing::stem_dir_correction (Grob*me, Item * rcolumn,
 	(head_posns[LEFT][DOWN] > head_posns[RIGHT][UP]) ? RIGHT : LEFT;
 
       Real delta = head_posns[-lowest][DOWN] - head_posns[lowest][UP] ;
-      Real corr = gh_scm2double (me->get_grob_property ("stem-spacing-correction"));
+      Real corr = robust_scm2double (me->get_grob_property ("stem-spacing-correction"), 0);
       corr =  (delta <= 1) ? 0.0 : 0.25;
       
       correction=  -lowest * corr ;
diff --git a/lily/percent-repeat-item.cc b/lily/percent-repeat-item.cc
index 2dbffcff35..4c87351d26 100644
--- a/lily/percent-repeat-item.cc
+++ b/lily/percent-repeat-item.cc
@@ -19,13 +19,13 @@
 Molecule
 Percent_repeat_item_interface::brew_slash ( Grob *me)
 {
-  Real slope = gh_scm2double (me->get_grob_property ("slope"));
+  Real slope = robust_scm2double (me->get_grob_property ("slope"), 1);
   Real wid = 2.0 / slope;
 
   /*
     todo: check out if in staff-rule thickness normally.
    */
-  Real thick = gh_scm2double (me->get_grob_property ("thickness"));
+  Real thick = robust_scm2double (me->get_grob_property ("thickness"), 1);
   Molecule m = Lookup::repeat_slash (wid, slope, thick);
   m.translate_axis (-m.extent (Y_AXIS).center (), Y_AXIS);
   return m;
diff --git a/lily/separation-item.cc b/lily/separation-item.cc
index 8b59a91967..bb8c4594db 100644
--- a/lily/separation-item.cc
+++ b/lily/separation-item.cc
@@ -67,11 +67,7 @@ Separation_item::conditional_width (Grob * me, Grob * left)
 
   SCM pad = me->get_grob_property ("padding");
 
-  if (gh_number_p (pad))
-    {
-      w[RIGHT] += gh_scm2double (pad)/2;
-      w[LEFT] -= gh_scm2double (pad)/2;    
-    }
+  w.widen (robust_scm2double (pad, 0.0));
   return w;
 }
 
@@ -116,11 +112,7 @@ Separation_item::width (Grob *me)
 
   SCM pad = me->get_grob_property ("padding");
 
-  if (gh_number_p (pad))
-  {
-    w[RIGHT] += gh_scm2double (pad)/2;
-    w[LEFT] -= gh_scm2double (pad)/2;    
-  }
+  w.widen (robust_scm2double (pad, 0.0));
 
   me->set_grob_property ("X-extent", ly_interval2scm (w));
   
diff --git a/lily/side-position-interface.cc b/lily/side-position-interface.cc
index ea15805b3e..f10f80073a 100644
--- a/lily/side-position-interface.cc
+++ b/lily/side-position-interface.cc
@@ -106,11 +106,7 @@ Side_position_interface::general_side_position (Grob * me, Axis a, bool use_exte
   SCM minimum = me->get_grob_property ("minimum-space");
 
   Real total_off = dim.linear_combination (dir) - off;
-  SCM padding = me->get_grob_property ("padding");
-  if (gh_number_p (padding))
-    {
-      total_off += gh_scm2double (padding) * dir;
-    }
+  total_off += robust_scm2double ( me->get_grob_property ("padding"), 0);
 
   if (gh_number_p (minimum) 
       && dir
@@ -228,11 +224,7 @@ Side_position_interface::out_of_staff (SCM element_smob, SCM axis)
   if (!st)
     return gh_int2scm (0);
 
-  Real padding=0.0;
-  SCM spad = me->get_grob_property ("staff-padding");
-
-  if (gh_number_p (spad))
-    padding = gh_scm2double (spad);
+  Real padding= robust_scm2double ( me->get_grob_property ("staff-padding"), 0);
   
   Grob *common = me->common_refpoint (st, Y_AXIS);
   Direction d = Side_position_interface::get_direction (me);
diff --git a/lily/slur.cc b/lily/slur.cc
index 4e2df22979..4e4150bc83 100644
--- a/lily/slur.cc
+++ b/lily/slur.cc
@@ -349,7 +349,7 @@ Slur::get_attachment (Grob *me, Direction dir,
 		Default position is on stem X, at stem end Y
 	       */
 	      Real stem_thickness =
-		gh_scm2double (stem->get_grob_property ("thickness"))
+		robust_scm2double (stem->get_grob_property ("thickness"), 1)
 		* stem->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
 	      o += Offset (0.5 *
 			   x_extent * (1 + Stem::get_direction (stem))
@@ -450,7 +450,7 @@ Slur::encompass_offset (Grob*me,
   /*
    leave a gap: slur mustn't touch head/stem
    */
-  o[Y_AXIS] += dir * gh_scm2double (me->get_grob_property ("y-free")) *
+  o[Y_AXIS] += dir * robust_scm2double (me->get_grob_property ("y-free"), 0) *
     1.0;
   return o;
 }
@@ -548,7 +548,7 @@ Slur::brew_molecule (SCM smob)
       return SCM_EOL;
     }
 
-  Real base_thick = gh_scm2double (me->get_grob_property ("thickness"));
+  Real base_thick = robust_scm2double (me->get_grob_property ("thickness"), 1);
 
   Real thick = base_thick *
     me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
@@ -563,7 +563,7 @@ Slur::brew_molecule (SCM smob)
   Molecule a;
   SCM d =  me->get_grob_property ("dashed");
   if (gh_number_p (d))
-    a = Lookup::dashed_slur (one, thick, thick * gh_scm2double (d));
+    a = Lookup::dashed_slur (one, thick, thick * robust_scm2double (d, 0));
   else
     a = Lookup::slur (one, get_grob_direction (me) * base_thick * ss / 10.0,
 		      thick);
@@ -580,7 +580,7 @@ Slur::set_control_points (Grob*me)
   SCM h_inf_scm = me->get_grob_property ("height-limit");
   SCM r_0_scm = me->get_grob_property ("ratio");
 
-  Real r_0 = gh_scm2double (r_0_scm);
+  Real r_0 = robust_scm2double (r_0_scm, 1);
   Real h_inf = staff_space * gh_scm2double (h_inf_scm);
   
   Slur_bezier_bow bb (get_encompass_offsets (me),
diff --git a/lily/spacing-spanner.cc b/lily/spacing-spanner.cc
index c582357f72..659216be56 100644
--- a/lily/spacing-spanner.cc
+++ b/lily/spacing-spanner.cc
@@ -164,7 +164,7 @@ void
 Spacing_spanner::prune_loose_columns (Grob*me,Link_array<Grob> *cols, Rational shortest)
 {
   Link_array<Grob> newcols;
-  Real increment = gh_scm2double (me->get_grob_property ("spacing-increment"));
+  Real increment = robust_scm2double (me->get_grob_property ("spacing-increment"), 1.2);
   for (int i=0; i < cols->size ();  i++)
     {
       if (Item::breakable_b (cols->elem(i)) || Paper_column::musical_b (cols->elem (i)))
@@ -508,7 +508,7 @@ void
 Spacing_spanner::do_measure (Rational shortest, Grob*me, Link_array<Grob> *cols) 
 {
 
-  Real headwid =       gh_scm2double (me->get_grob_property ("spacing-increment"));
+  Real headwid = robust_scm2double (me->get_grob_property ("spacing-increment"), 1);
   for (int i= 0; i < cols->size () - 1; i++)
     {
       Item * l = dynamic_cast<Item*> (cols->elem (i));
@@ -695,7 +695,7 @@ Spacing_spanner::standard_breakable_column_spacing (Grob * me, Item*l, Item*r,
       if (dt)
 	mlen = *dt;
       
-      Real incr = gh_scm2double (me->get_grob_property ("spacing-increment"));
+      Real incr = robust_scm2double (me->get_grob_property ("spacing-increment"), 1);
 
       *space =  *fixed + incr * double (mlen.main_part_ / shortest.main_part_) * 0.8;
     }
@@ -812,8 +812,8 @@ Spacing_spanner::breakable_column_spacing (Grob*me, Item* l, Item *r,Moment shor
 Real
 Spacing_spanner::get_duration_space (Grob*me, Moment d, Rational shortest, bool * expand_only) 
 {
-  Real k = gh_scm2double (me->get_grob_property ("shortest-duration-space"));
-  Real incr = gh_scm2double (me->get_grob_property ("spacing-increment"));
+  Real k = robust_scm2double (me->get_grob_property ("shortest-duration-space"), 1);
+  Real incr = robust_scm2double (me->get_grob_property ("spacing-increment"), 1);
   
   if (d < shortest)
     {
@@ -928,10 +928,8 @@ Spacing_spanner::note_spacing (Grob*me, Grob *lc, Grob *rc,
       */
       dist = get_duration_space (me, shortest, shortest.main_part_, expand_only);
 
-      Real grace_fact = 1.0;
-      SCM gf = me->get_grob_property ("grace-space-factor");
-      if (gh_number_p (gf))
-	grace_fact = gh_scm2double (gf);
+      Real grace_fact
+	= robust_scm2double (me->get_grob_property ("grace-space-factor"), 1);
 
       dist *= grace_fact;
     }
diff --git a/lily/spanner.cc b/lily/spanner.cc
index 0b444d45fe..a126483203 100644
--- a/lily/spanner.cc
+++ b/lily/spanner.cc
@@ -336,7 +336,7 @@ Spanner::set_spacing_rods (SCM smob)
   r.item_l_drul_[LEFT] = sp->get_bound (LEFT);
   r.item_l_drul_[RIGHT] = sp->get_bound (RIGHT);
   r.distance_ =
-    gh_scm2double (me->get_grob_property ("minimum-length"));
+    robust_scm2double (me->get_grob_property ("minimum-length"), 0);
 
   r.add_to_cols ();
   return SCM_UNSPECIFIED;
diff --git a/lily/staff-spacing.cc b/lily/staff-spacing.cc
index dab496820d..726a6981d6 100644
--- a/lily/staff-spacing.cc
+++ b/lily/staff-spacing.cc
@@ -78,7 +78,7 @@ Staff_spacing::next_note_correction (Grob * me,
 
 	    Real corr = abs (stem_posns.length ()/7.) <? 1.0;
 	    corr *=
-	      gh_scm2double (me->get_grob_property ("stem-spacing-correction"));
+	      robust_scm2double (me->get_grob_property ("stem-spacing-correction"), 1);
 
 	    if (d != DOWN)
 	      corr = 0.0;
@@ -106,7 +106,7 @@ Staff_spacing::bar_y_positions (Grob *bar_grob)
 	{
 	  SCM sz = Bar_line::get_staff_bar_size (bar_grob->self_scm());
 	  bar_size = Interval (-1,1);
-	  bar_size *= gh_scm2double (sz)
+	  bar_size *= robust_scm2double (sz, 1)
 	    / Staff_symbol_referencer::staff_space (bar_grob);
 	}
     }
diff --git a/lily/staff-symbol-referencer.cc b/lily/staff-symbol-referencer.cc
index 47e6977ff8..0ce4f1aa0a 100644
--- a/lily/staff-symbol-referencer.cc
+++ b/lily/staff-symbol-referencer.cc
@@ -64,14 +64,8 @@ Staff_symbol_referencer::get_position (Grob*me)
 
       p += 2.0 * y / Staff_symbol::staff_space (st);
     }
-  else
-    {
-      SCM pos = me->get_grob_property ("staff-position");
-      if (gh_number_p (pos))
-	return gh_scm2double (pos);
-    }
-  
-  return  p;
+
+  return robust_scm2double ( me->get_grob_property ("staff-position"), p);
 }
 
 
diff --git a/lily/staff-symbol.cc b/lily/staff-symbol.cc
index c8db2f4812..69a332b6a1 100644
--- a/lily/staff-symbol.cc
+++ b/lily/staff-symbol.cc
@@ -63,9 +63,7 @@ Staff_symbol::brew_molecule (SCM smob)
     }
 
   Real t = me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
-  SCM my_thick = me->get_grob_property("thickness");
-  if (gh_number_p (my_thick))
-    t *= gh_scm2double (my_thick);
+  t *= robust_scm2double ( me->get_grob_property("thickness"), 1.0);
   
   int l = Staff_symbol::line_count (me);
   
@@ -102,12 +100,7 @@ Staff_symbol::line_count (Grob*me)
 Real
 Staff_symbol::staff_space (Grob*me)
 {
-  Real ss = 1.0;
-  
-  SCM s = me->get_grob_property ("staff-space");
-  if (gh_number_p (s))
-    ss *= gh_scm2double (s);
-  return ss;
+  return  robust_scm2double ( me->get_grob_property ("staff-space"), 1.0);
 }
 
 
diff --git a/lily/stem-tremolo.cc b/lily/stem-tremolo.cc
index 6ca35377f9..886c9df71d 100644
--- a/lily/stem-tremolo.cc
+++ b/lily/stem-tremolo.cc
@@ -80,8 +80,8 @@ Stem_tremolo::raw_molecule (Grob *me)
     dydx = 0.25;
 
   Real ss = Staff_symbol_referencer::staff_space (me);
-  Real thick = gh_scm2double (me->get_grob_property ("beam-thickness"));
-  Real width = gh_scm2double (me->get_grob_property ("beam-width"));
+  Real thick = robust_scm2double (me->get_grob_property ("beam-thickness"),1);
+  Real width = robust_scm2double (me->get_grob_property ("beam-width"),1);
   Real blot = me->get_paper ()->get_realvar (ly_symbol2scm ("blotdiameter"));
 
   width *= ss;
diff --git a/lily/stem.cc b/lily/stem.cc
index ce26886866..cda3175f75 100644
--- a/lily/stem.cc
+++ b/lily/stem.cc
@@ -318,15 +318,12 @@ Stem::get_default_stem_end_position (Grob*me)
       || (get_direction (me) != get_default_dir (me)))
     {
       
-      Real shorten = 0.0;
   
       SCM sshorten = me->get_grob_property ("stem-shorten");
       SCM scm_shorten = gh_pair_p (sshorten) ?
 	robust_list_ref ((duration_log (me) - 2) >? 0, sshorten): SCM_EOL;
-      if (gh_number_p (scm_shorten))
-	{
-	  shorten = 2* gh_scm2double (scm_shorten);
-	}
+      Real shorten = 2* robust_scm2double (scm_shorten,0);
+      
   
       /* On boundary: shorten only half */
       if (abs (head_positions (me)[get_direction (me)]) <= 1)
@@ -454,7 +451,7 @@ Stem::position_noteheads (Grob*me)
     heads.reverse ();
 
 
-  Real thick = gh_scm2double (me->get_grob_property ("thickness"))
+  Real thick = robust_scm2double (me->get_grob_property ("thickness"),1)
      * me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
       
   Grob *hed = support_head (me);
@@ -745,7 +742,7 @@ Stem::brew_molecule (SCM smob)
 
   
   // URG
-  Real stem_width = gh_scm2double (me->get_grob_property ("thickness"))
+  Real stem_width = robust_scm2double (me->get_grob_property ("thickness"), 1)
     * me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
   Real blot = 
 	me->get_paper ()->get_realvar (ly_symbol2scm ("blotdiameter"));
@@ -808,7 +805,7 @@ Stem::off_callback (SCM element_smob, SCM)
       if (attach)
 	{
 	  Real rule_thick
-	    = gh_scm2double (me->get_grob_property ("thickness"))
+	    = robust_scm2double (me->get_grob_property ("thickness"), 1)
 	    * me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
 	  
 	  r += - d * rule_thick * 0.5;
@@ -854,7 +851,7 @@ Stem::calc_stem_info (Grob *me)
   Real staff_space = Staff_symbol_referencer::staff_space (me);
   Grob *beam = get_beam (me);
   Real beam_translation = Beam::get_beam_translation (beam);
-  Real beam_thickness = gh_scm2double (beam->get_grob_property ("thickness"));
+  Real beam_thickness = robust_scm2double (beam->get_grob_property ("thickness"), 1);
   int beam_count = Beam::get_direction_beam_count (beam, my_dir);
 
 
@@ -928,9 +925,7 @@ Stem::calc_stem_info (Grob *me)
     }
 
 
-  SCM shorten = beam->get_grob_property ("shorten");
-  if (gh_number_p (shorten))
-    ideal_y -= gh_scm2double (shorten);
+  ideal_y -= robust_scm2double (beam->get_grob_property ("shorten"), 0);
 
   Real minimum_free =
     gh_scm2double (robust_list_ref
diff --git a/lily/system-start-delimiter-engraver.cc b/lily/system-start-delimiter-engraver.cc
index d8045610bd..df94b83400 100644
--- a/lily/system-start-delimiter-engraver.cc
+++ b/lily/system-start-delimiter-engraver.cc
@@ -56,7 +56,7 @@ System_start_delimiter_engraver::acknowledge_grob (Grob_info inf)
        {
          inf.grob_->translate_axis ( -0.8, X_AXIS); // ugh
          inf.grob_->set_grob_property ("arch-height",
-           gh_double2scm(gh_scm2double(inf.grob_->get_grob_property
+				       gh_double2scm (gh_scm2double(inf.grob_->get_grob_property
                                        ("arch-height"))+0.5));
        }
     }
diff --git a/lily/system-start-delimiter.cc b/lily/system-start-delimiter.cc
index 0714d819e7..4b7c49835f 100644
--- a/lily/system-start-delimiter.cc
+++ b/lily/system-start-delimiter.cc
@@ -63,7 +63,7 @@ Molecule
 System_start_delimiter::simple_bar (Grob*me,Real h) 
 {
   Real lt =me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness")) ;
-  Real w = lt * gh_scm2double (me->get_grob_property ("thickness"));
+  Real w = lt * robust_scm2double (me->get_grob_property ("thickness"), 1);
   return Lookup::round_filled_box (Box (Interval (0,w), Interval (-h/2, h/2)),
 				   lt);
 }
@@ -112,7 +112,6 @@ System_start_delimiter::brew_molecule (SCM smob)
   if (!gh_string_p (s))
     return SCM_EOL;
   SCM gsym = scm_string_to_symbol (s) ;
-  SCM c = me->get_grob_property ("collapse-height");
   
   Real staff_space = Staff_symbol_referencer::staff_space (me);
   Interval ext = ly_scm2interval (Axis_group_interface::group_extent_callback
@@ -120,7 +119,7 @@ System_start_delimiter::brew_molecule (SCM smob)
   Real l = ext.length () / staff_space;
   
   if (ext.is_empty ()
-      || (gh_number_p (c) && l <= gh_scm2double (c)))
+      || (robust_scm2double (me->get_grob_property ("collapse-height"), 0.0) >= l))
     {
       me->suicide ();
       return SCM_EOL;
diff --git a/lily/text-spanner.cc b/lily/text-spanner.cc
index b575850ed4..c1025bd54c 100644
--- a/lily/text-spanner.cc
+++ b/lily/text-spanner.cc
@@ -40,10 +40,7 @@ Text_spanner::brew_molecule (SCM smob)
   Spanner *spanner = dynamic_cast<Spanner*> (me);
   
   /* Ugh, must be same as Hairpin::brew_molecule.  */
-  Real padding = 0.0;
-  SCM itp= me->get_grob_property ("if-text-padding");
-  if (gh_number_p (itp))
-    padding = gh_scm2double (itp);
+  Real padding = robust_scm2double ( me->get_grob_property ("if-text-padding"), 0);
 
   Grob *common = spanner->get_bound (LEFT)->common_refpoint (spanner->get_bound (RIGHT), X_AXIS);
   Paper_def * paper = me->get_paper();
@@ -116,7 +113,7 @@ Text_spanner::brew_molecule (SCM smob)
 	    continue;
 	  
 	  Real dx = 0.0;
-	  if (gh_pair_p (flare))
+	  if (is_number_pair (flare))
 	    dx = gh_scm2double (index_get_cell (flare, d)) * d;
 
 	  Real dy = - dir * edge_height[d] ;
diff --git a/lily/tie.cc b/lily/tie.cc
index 846acaa28f..85d838f02d 100644
--- a/lily/tie.cc
+++ b/lily/tie.cc
@@ -130,7 +130,7 @@ Tie::get_control_points (SCM smob)
   
   Real staff_space = Staff_symbol_referencer::staff_space (me);
 
-  Real x_gap_f = gh_scm2double (me->get_grob_property ("x-gap"));
+  Real x_gap_f = robust_scm2double (me->get_grob_property ("x-gap"), 0);
 
   Grob* l = me->get_bound (LEFT);
   Grob* r = me->get_bound (RIGHT);  
diff --git a/lily/tuplet-bracket.cc b/lily/tuplet-bracket.cc
index a499f29690..2c9705d0b4 100644
--- a/lily/tuplet-bracket.cc
+++ b/lily/tuplet-bracket.cc
@@ -117,8 +117,8 @@ Tuplet_bracket::brew_molecule (SCM smob)
       after_line_breaking (smob);
   }
   
-  Real ly = gh_scm2double (me->get_grob_property ("left-position"));
-  Real ry = gh_scm2double (me->get_grob_property ("right-position"));  
+  Real ly = robust_scm2double (me->get_grob_property ("left-position"), 0);
+  Real ry = robust_scm2double (me->get_grob_property ("right-position"), 0);  
   
   bool equally_long = false;
   Grob * par_beam = parallel_beam (me, columns, &equally_long);
diff --git a/lily/vaticana-ligature-engraver.cc b/lily/vaticana-ligature-engraver.cc
index cf960ca8bf..896cd42362 100644
--- a/lily/vaticana-ligature-engraver.cc
+++ b/lily/vaticana-ligature-engraver.cc
@@ -349,33 +349,9 @@ void
 Vaticana_ligature_engraver::transform_heads (Spanner *ligature,
 					     Array<Grob_info> primitives)
 {
-  Real flexa_width;
-  SCM flexa_width_scm = ligature->get_grob_property ("flexa-width");
-  if (flexa_width_scm != SCM_EOL)
-    {
-      flexa_width = gh_scm2double (flexa_width_scm);
-    }
-  else
-    {
-      ligature->programming_error ("Vaticana_ligature_engraver:"
-				   "flexa-width undefined; "
-				   "assuming 2.0 staff space");
-      flexa_width =
-	2.0 * Staff_symbol_referencer::staff_space (ligature);
-    }
+  Real flexa_width= robust_scm2double ( ligature->get_grob_property ("flexa-width"), 2);
 
-  Real thickness;
-  SCM thickness_scm = ligature->get_grob_property ("thickness");
-  if (thickness_scm != SCM_EOL)
-    {
-      thickness = gh_scm2double (thickness_scm);
-    }
-  else
-    {
-      ligature->programming_error ("Vaticana_ligature_engraver:"
-				   "thickness undefined; assuming 1.0");
-      thickness = 1.0;
-    }
+  Real thickness= robust_scm2double ( ligature->get_grob_property ("thickness"), 1);
 
   Item *prev_primitive = 0;
   int prev_prefix_set = 0;
diff --git a/lily/vaticana-ligature.cc b/lily/vaticana-ligature.cc
index e97a7f0f08..2368aa36fc 100644
--- a/lily/vaticana-ligature.cc
+++ b/lily/vaticana-ligature.cc
@@ -92,18 +92,7 @@ vaticana_brew_flexa (Grob *me,
       me->warning (_ ("ascending vaticana style flexa"));
     }
 
-  Real width;
-  SCM flexa_width_scm = me->get_grob_property ("flexa-width");
-  if (flexa_width_scm != SCM_EOL)
-    {
-      width = gh_scm2double (flexa_width_scm);
-    }
-  else
-    {
-      me->warning ("Vaticana_ligature: "
-		   "flexa-width undefined; assuming 2.0");
-      width = 2.0 * staff_space;
-    }
+  Real width = robust_scm2double ( me->get_grob_property ("flexa-width"), 2);
 
   /*
    * Compensate curve thickness that appears to be smaller in steep
@@ -238,19 +227,7 @@ vaticana_brew_primitive (Grob *me, bool ledger_take_space)
 
   Molecule out;
   int flexa_height = 0;
-  Real thickness;
-
-  SCM thickness_scm = me->get_grob_property ("thickness");
-  if (thickness_scm != SCM_EOL)
-    {
-      thickness = gh_scm2double (thickness_scm);
-    }
-  else
-    {
-      me->programming_error ("Vaticana_ligature: "
-			     "thickness undefined; assuming 1.0");
-      thickness = 1.0;
-    }
+  Real thickness = robust_scm2double ( me->get_grob_property ("thickness"), 1);
 
   Real line_thickness =
     thickness * me->get_paper ()->get_realvar (ly_symbol2scm ("linethickness"));
@@ -267,17 +244,7 @@ vaticana_brew_primitive (Grob *me, bool ledger_take_space)
   else
     delta_pitch = 0;
 
-  Real x_offset = 0.0;
-  SCM x_offset_scm = me->get_grob_property ("x-offset");
-  if (x_offset_scm != SCM_EOL)
-    {
-      x_offset = gh_scm2double (x_offset_scm);
-    }
-  else
-    {
-      me->programming_error ("Vaticana_ligature: "
-			     "x-offset undefined; assuming 0.0");
-    }
+  Real x_offset = robust_scm2double ( me->get_grob_property ("x-offset"), 0);
 
   bool add_stem = to_boolean (me->get_grob_property ("add-stem"));
   bool add_cauda = to_boolean (me->get_grob_property ("add-cauda"));
@@ -293,18 +260,7 @@ vaticana_brew_primitive (Grob *me, bool ledger_take_space)
        * flexa_width.)
        */
       Real staff_space = Staff_symbol_referencer::staff_space (me);
-      Real flexa_width;
-      SCM flexa_width_scm = me->get_grob_property ("flexa-width");
-      if (flexa_width_scm != SCM_EOL)
-	{
-	  flexa_width = gh_scm2double (flexa_width_scm);
-	}
-      else
-	{
-	  me->warning ("Vaticana_ligature: "
-		       "flexa-width undefined; assuming 2.0");
-	  flexa_width = 2.0 * staff_space;
-	}
+      Real flexa_width  = robust_scm2double ( me->get_grob_property ("flexa-width"), 2);
       out =
 	Lookup::blank (Box (Interval (0, 0.5*flexa_width), Interval (0,0)));
     }
diff --git a/lily/volta-bracket.cc b/lily/volta-bracket.cc
index 740054f775..bf2205f46f 100644
--- a/lily/volta-bracket.cc
+++ b/lily/volta-bracket.cc
@@ -89,7 +89,7 @@ Volta_bracket_interface::brew_molecule (SCM smob)
     }
 
   Real w = dynamic_cast<Spanner*> (me)->spanner_length () - left - half_space;
-  Real h =  gh_scm2double (me->get_grob_property ("height"));
+  Real h =  robust_scm2double (me->get_grob_property ("height"), 1);
 
   Molecule start,end ;
   if (!no_vertical_start)
-- 
2.39.2