From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andy Wingo <wingo@igalia.com>
Subject: Re: question regarding substitute* and #t
Date: Wed, 24 Jan 2018 16:20:36 +0100
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In-Reply-To: <87h8rbtmhl.fsf@netris.org> (Mark H. Weaver's message of "Wed, 24
	Jan 2018 08:28:06 -0500")
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To: Mark H Weaver <mhw@netris.org>
Cc: guix-devel@gnu.org

On Wed 24 Jan 2018 14:28, Mark H Weaver <mhw@netris.org> writes:

> Andy Wingo <wingo@igalia.com> writes:
>
>> On Wed 24 Jan 2018 13:06, Mark H Weaver <mhw@netris.org> writes:
>>
>>> +             ;; Install to the right directory
>>> +             (substitute* '("Makefile"
>>> +                            "Qsci/Makefile")
>>> +               (("\\$\\(INSTALL_ROOT\\)/gnu/store/[^/]+")
>>> +                (assoc-ref outputs "out")))
>>> +             #t)))))
>>
>> I guess once we switch over all instances of "system" and "system*" to
>> use invoke, does that mean we will also be able to remove these
>> vestigial "#t" returns?
>
> After we switch to using 'invoke' everywhere, or more precisely, after
> we arrange to never return #false from any phase or snippet, then there
> should be one more step before removing the vestigial #true returns: we
> should change the code that calls phases or snippets to ignore the
> value(s) returned by those procedures.  When that is done, then the #t's
> will truly be vestigial.  Does that make sense?

Sure, makes sense.  Thanks for thinking it through with me :)

Andy