string-every returns #f when applied to an empty sequence

string-every returns #f when applied to an empty sequence

["Andreas Vögele"]

According to SRFI-13 the procedure string-every returns #t if it is applied
to an empty sequence (see
http://srfi.schemers.org/srfi-13/srfi-13.html#Predicates). But Guile's
implementation returns #f. Is this a bug in SRFI-13 or in srfi/srfi-13.c?



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Re: string-every returns #f when applied to an empty sequence

[Kevin Ryde]

"Andreas Vögele" <voegelas@gmx.net> writes:
>
> According to SRFI-13 the procedure string-every returns #t if it is applied
> to an empty sequence (see
> http://srfi.schemers.org/srfi-13/srfi-13.html#Predicates). But Guile's
> implementation returns #f. Is this a bug in SRFI-13 or in srfi/srfi-13.c?

Thanks.  If it's contrary to the spec then it's a bug in guile.

Looks like guile also doesn't make the final predicate application a
tail call the way the spec describes.  Not sure how to fix that.


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Re: string-every returns #f when applied to an empty sequence

[Rob Browning]

Kevin Ryde <user42@zip.com.au> writes:

> Thanks.  If it's contrary to the spec then it's a bug in guile.
>
> Looks like guile also doesn't make the final predicate application a
> tail call the way the spec describes.  Not sure how to fix that.

Actually, we can change it so that we handle the last invocation
specially, i.e. "return scm_call_1(...);".

If we're going to implement string-every in C, then that's the best we
can do right now, and from looking at the output of srfi-13.s via
-save-temps (presuming I'm reading the x86 assembly right) newer gcc's
optimize that call to a jmp.

-- 
Rob Browning
rlb @defaultvalue.org and @debian.org; previously @cs.utexas.edu
GPG starting 2002-11-03 = 14DD 432F AE39 534D B592  F9A0 25C8 D377 8C7E 73A4


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Re: string-every returns #f when applied to an empty sequence

[Kevin Ryde]

Rob Browning <rlb@defaultvalue.org> writes:
>
> If we're going to implement string-every in C, then that's the best we
> can do right now, and from looking at the output of srfi-13.s via
> -save-temps (presuming I'm reading the x86 assembly right) newer gcc's
> optimize that call to a jmp.

I wouldn't worry, unless everything else in the eval path is optimized
that way too.  Even then it's relying on a new enough gcc.


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