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From: dempson@actrix.gen.nz (David Empson)
Newsgroups: comp.sys.apple2.gno
Subject: Re: dmake recipe
Date: Thu, 16 Apr 1998 04:47:45 +1200
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Sönke Behrens <sbehrens@bigfoot.com> wrote:

> Dragon King <markhj01@visi.com> wrote:
> 
> >Just thought I'd share a recipe I've come up with to help with making
> >object libraries from dmake(1).
> >
> >  %$A : ; $(AR) $(ARFLAGS) $@ +$(?:t" +")
> 
> Thanks for sharing that. Wow. Looks complicated. Been a while since I
> had a close enough look at dmake to actually understand this. Care to
> break it into its component parts and explain how it works?
> 
> Might help others on this group to get a better understanding of
> dmake, too ;-)

Yes, indeed.  I know normal make, but I've never looked at dmake.  Most
of that makes vague sense, but some parts are unfamiliar.

Here is my guess (which I'm sure will be corrected and/or clarified):

I have no idea what the % in front of $A means, unless it is required to
distinguish a rule from a macro definition.  I assume $A is the macro
which contains the name of the object library.  The colon appears to
separate the target from the dependents list.  There are no dependents
here, so this rule will always be executed.  The semicolon separates the
dependents list from the command to build the target.

$(AR) is the macro containing the command (presumably AR for ARCHIVER,
thus the macro will be set to mklib or equivalent), and $(ARFLAGS) is
the optional flags for the archiver.  $@ is the target name for this
rule, which is the first non-flag parameter to the archiver program.

As to the rest of it - this looks like some kind of regular expression
(perl uses (?:...) as a special grouping notation).  My guess: it
expands into a list of files to be included in the library, each of
which will be separated by a space and a plus sign.  The initial plus is
the prefix for the first file.

Assuming I'm right, this means the general form is $(?:macro"sep") where
'macro' is the macro name and 'sep' is the text to separate each word in
the macro.  For example, if t is defined as:

t = fileA fileB fileC

then $(?:t" +") will expand to

  fileA +fileB +fileC

(The quoted rule adds an initial '+' explictly, on the assumption that
there is at least one object file to be added to the library.)

This means that $(?:t" ") is exactly the same as $t, assuming the words
in the macro 't' are separated by single spaces in its definition.

I invented a similar mechanism in my own version of make (which I use on
the PC at work), but my notation is $e(macro, prefix, sep, suffix).
This allows file extensions and paths to be added to each word in a
macro.

So how did I do?  :-)

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand