+
+LY_DEFINE(ly_molecule_combined_at_edge,
+ "ly-combine-molecule-at-edge",
+ 5 , 0, 0, (SCM first, SCM axis, SCM direction,
+ SCM second, SCM padding),
+ "Construct a molecule by putting @var{second} next to
+@var{first}. @var{axis} can be 0 (x-axis) or 1 (y-axis), @var{direction} can be
+-1 (left or down) or 1 (right or up). @var{padding} specifies extra
+space to add in between measured in global staff space.")
+
+{
+ Molecule * m1 = unsmob_molecule (first);
+ Molecule * m2 = unsmob_molecule (second);
+ Molecule result;
+
+
+ SCM_ASSERT_TYPE(ly_axis_p (axis), axis, SCM_ARG2, __FUNCTION__, "axis");
+ SCM_ASSERT_TYPE(ly_dir_p (direction), direction, SCM_ARG3, __FUNCTION__, "dir");
+ SCM_ASSERT_TYPE(gh_number_p (padding), padding, SCM_ARG4, __FUNCTION__, "number");
+
+ if (m1)
+ result = *m1;
+ if (m2)
+ result.add_at_edge (Axis (gh_scm2int (axis)), Direction (gh_scm2int (direction)),
+ *m2, gh_scm2double (padding));
+
+ return result.smobbed_copy ();
+}
+
+/*
+ FIXME: support variable number of arguments "
+ */
+LY_DEFINE(ly_add_molecule ,
+ "ly-add-molecule", 2, 0,0,(SCM first, SCM second),
+ "Combine two molecules."
+ )
+{
+ Molecule * m1 = unsmob_molecule (first);
+ Molecule * m2 = unsmob_molecule (second);
+ Molecule result;
+
+
+ if (m1)
+ result = *m1;
+ if (m2)
+ result.add_molecule (*m2);
+
+ return result.smobbed_copy ();
+}
+
+LY_DEFINE(ly_make_molecule,
+ "ly-make-molecule", 3, 0, 0, (SCM expr, SCM xext, SCM yext),
+ "
+The objective of any typesetting system is to put ink on paper in the
+right places. For LilyPond, this final stage is left to the @TeX{} and
+the printer subsystem. For lily, the last stage in processing a score is
+outputting a description of what to put where. This description roughly
+looks like
+@example
+ PUT glyph AT (x,y)
+ PUT glyph AT (x,y)
+ PUT glyph AT (x,y)
+@end example
+you merely have to look at the tex output of lily to see this.
+Internally these instructions are encoded in Molecules.@footnote{At some
+point LilyPond also contained Atom-objects, but they have been replaced
+by Scheme expressions, making the name outdated.} A molecule is
+what-to-print-where information that also contains dimension information
+(how large is this glyph?).
+
+Conceptually, Molecules can be constructed from Scheme code, by
+translating a Molecule and by combining two molecules. In BNF
+notation:
+
+@example
+Molecule :: COMBINE Molecule Molecule
+ | TRANSLATE Offset Molecule
+ | GLYPH-DESCRIPTION
+ ;
+@end example
+
+If you are interested in seeing how this information is stored, you
+can run with the @code{-f scm} option. The scheme expressions are then
+dumped in the output file.")
+{
+ SCM_ASSERT_TYPE (ly_number_pair_p (xext), xext, SCM_ARG2, __FUNCTION__, "number pair");
+ SCM_ASSERT_TYPE (ly_number_pair_p (yext), yext, SCM_ARG3, __FUNCTION__, "number pair");
+
+ Box b (ly_scm2interval (xext), ly_scm2interval(yext));
+ Molecule m (b, expr);
+ return m.smobbed_copy ();
+}
+
+SCM
+fontify_atom (Font_metric * met, SCM f)
+{
+ if (f == SCM_EOL)
+ return f;
+ else
+ return scm_list_n (ly_symbol2scm ("fontify"),
+ ly_quote_scm (met->description_), f, SCM_UNDEFINED);
+}
+
+LY_DEFINE(ly_fontify_atom,"ly-fontify-atom", 2, 0, 0,
+ (SCM met, SCM f),
+ "Add a font selection command for the font metric @var{met} to @var{f}.")
+{
+ SCM_ASSERT_TYPE(unsmob_metrics (met), met, SCM_ARG1, __FUNCTION__, "font metric");
+
+ return fontify_atom (unsmob_metrics (met), f);
+}
+LY_DEFINE(ly_align_to_x,"ly-align-to!", 3, 0, 0, (SCM mol, SCM axis, SCM dir),
+ "Align @var{mol} using its own extents.")
+{
+ SCM_ASSERT_TYPE(unsmob_molecule (mol), mol, SCM_ARG1, __FUNCTION__, "molecule");
+ SCM_ASSERT_TYPE(ly_axis_p (axis), axis, SCM_ARG2, __FUNCTION__, "axis");
+ SCM_ASSERT_TYPE(ly_dir_p (dir), dir, SCM_ARG3, __FUNCTION__, "dir");
+
+ unsmob_molecule (mol)->align_to ((Axis)gh_scm2int (axis), Direction (gh_scm2int (dir)));
+
+ return SCM_UNDEFINED;
+}
+
+
+
+/*
+ Hmm... maybe this is not such a good idea ; stuff can be empty,
+ while expr_ == '()
+ */
+bool
+Molecule::empty_b () const