Re: Long live length in the docs. (issue 4965053)

[Trevor Daniels]

> 1) Trevor - I still haven't heard word back about ly:dimension?. 
> If it
> turns out this is not what's supposed to be used, please feel free 
> to
> change it to number? in a separate commit.

The dimension type was first introduced in 2003 in
lily/lily-guile.cc: a2a77093b49bca4f040944a0b4ec16f3beca05ec

+LY_DEFINE(ly_dimension_p,  "ly:dimension?", 1, 0, 0, (SCM d),
+   "Return @var{d} is a number. Used to distinguish length "
+   "variables from normal numbers.")
+{
+  return scm_number_p (d);
+}

It's now in lily/general-scheme.cc, essentially unchanged:

LY_DEFINE (ly_dimension_p, "ly:dimension?", 1, 0, 0, (SCM d),
          "Return @var{d} as a number.  Used to distinguish length"
          " variables from normal numbers.")
{
 return scm_number_p (d);
}

So the check for the dimension type is identical to that
for number.  Nevertheless, the two appear to be consistently
used in ly sources to indicate their different natures.
As 'stem-begin-position is not a length I'll change its
type to number.

Trevor