Re: DOCS: include a sample "Makefile"?

[Werner LEMBERG]

> INPUTS= $(wildcard *.ly)

IMHO, exactly THIS statement should be replaced with an explicit list
of all input files so that you can disable or enable files at your
wish.  Using the `\' character to suppress the end of line, you can
structure this very nicely:

  INPUTS = \
    foo-a.ly \
    foo-b.ly \
             \
    bar-x.ly \
    bar-y.ly \
    ...

If you are using GNU make, this can be also stated as

  INPUTS += foo-a.ly
  INPUTS += foo-b.ly
  ...

which makes it very easy to comment out the unused lines.

> if I run "make score" again (while there's a current pdf output of
> the file in the PDF dir), instead of saying it's up-to-date, it
> compiles the file again.  Can you tell me which part of the makefile
> keeps track of the pdf output?
>
> [...]
>
> .ly.pdf:
>       ${LILY_CMD} $<
>
> %.pdf %.midi: %.ly

Hmm.  You give the same (well, almost the same) rule twice.  This
old-fashioned (but fully portable) suffix rule

  .x.y:
      foo

is the same as this GNU make pattern rule:

  %.x: %.y
      foo

However, this pattern rule

  %.pdf %.midi: %.ly
      foo

says that both %.pdf and %.midi depend on %.ly, and `foo' generates
them both with a single invocation.  (You can't express this with an
old-fashioned suffix rule).  Having only

  %.pdf %.midi: %.ly
      $(LILY_CMD) $<

is thus sufficient.

One thing is still missing: The makefile must find the botu the input
and output files to check whether something needs to be remade.  This
explicit rule:

  score: PDF/${piece}.pdf
      $(LILY_CMD) Scores/${piece}.ly
      mv ${piece}.pdf PDF/

directly mentions that the output file is created in the `PDF'
subdirectory.  The above pattern rule doesn't know that.  This is the
reason why your files are made again and again if you use the `score'
target.

The solution to this problem is to use the special VPATH variable of
`make' which lists the directories for both targets and prerequisites.
A limitation is that the directories in `VPATH' are not expanded and
must be given directly (this seems to be undocumented; I'll contact
the GNU make people):

  VPATH = /your/dir/Scores /your/dir/PDF

  %.pdf %.midi: %.ly
      cd PDF; $(LILY_CMD) $<

Note that you can't say

  %.pdf %.midi: %.ly
      cd PDF
      $(LILY_CMD) $<

since `make' invokes the shell for each line separately, so the second
command doesn't see the `cd PDF' at all.

Finally, the `score' target can be simplified to

  score: $(piece).pdf

The pattern rule does the rest.

> Also, what is the significance of the curly braces instead of
> parentheses in ${piece}?

Both do exactly the same.

See below for something which works fine for me.


    Werner


======================================================================

piece = stamitz

LILY_CMD = lilypond -ddelete-intermediate-files \
                    -dno-point-and-click

.SUFFIXES: .ly .pdf .midi

VPATH = /your/dir/Scores /your/dir/PDF

%.pdf %.midi: %.ly
        cd PDF; $(LILY_CMD) $<

.PHONY: score
score: ${piece}.pdf