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bug#59221: (file-exists? #f) raises an exception

From: Joshua Branson
Subject: bug#59221: (file-exists? #f) raises an exception
Date: Wed, 16 Nov 2022 10:27:34 -0500
User-agent: Gnus/5.13 (Gnus v5.13)

Jean Abou Samra <jean@abou-samra.fr> writes:

> Le 13/11/2022 à 07:44, tomas@tuxteam.de a écrit :
>> You both have a point. Checking for existing predicates with a
>> longer tradition, though:
>>    scheme@(guile-user)> (exact? "mumble")
>>    ice-9/boot-9.scm:1685:16: In procedure raise-exception:
>>    In procedure exact?: Wrong type argument in position 1: "mumble"
>> seems to support Jean Abu's position that it is more customary to
>> raise for an argument of the wrong type. Also `string<?', etc.
>> do this. That seems to be the consensus.
> Yes. I am not sure where the people in the Guile IRC got the idea
> that a predicate shouldn't raise an exception. Lots of predicates in
> Guile do, and that is very helpful because it catches mistakes.
>> Naively, it just feel like it (file-exists? #f) should return #f.
> Why?

hmmm, somehow I missed your response.  I guess for my simple use case,
it just made more sense.  I am defining a service for guix that asks for
user input.  If the user doesn't type in input, the default value was

That's fine.  Thanks for all's replies.  I'll go ahead and close this


>> Would there be an objection to changing the definition of file-exists to
>> (define (file-exists file)
>>      (and (string? file)
>>           (old-file-exists-code file)))
> It would be inconsistent with the rest of Guile and I don't
> see what it would help with.
> Best,
> Jean

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