[gambit-list] check vs null

Pavel Dudrenov dudrenov at gmail.com
Sat Feb 14 18:01:56 EST 2009


If `get-foo' is an FFI and returns an object created in that foreign
environment, then perhaps it's better if you keep any predicates
related such objects in that foreign environment as well. Then just
implement the appropriate FFIs in gambit.

Pavel


On Sat, Feb 14, 2009 at 2:32 PM, lowly coder
<lowlycoder at huoyanjinjing.com> wrote:
> it works now; thanks!
>
> the main reason I posted to gambit rather than #scheme ... is that this
> seems a C-FFI (thus implementation specific question, not a generic scheme
> question)
>
> if I'm wrong ... please point out what scheme standard defines how NULLS
> from C-FFI/land is handled in scheme?
>
> On Sat, Feb 14, 2009 at 2:26 PM, Marijn Schouten (hkBst) <hkBst at gentoo.org>
> wrote:
>>
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>> lowly coder wrote:
>> > suppose I have c code of:
>> >
>> > [1] foo *bar = get_foo();
>> > [2] if (bar != NULL) { ... }
>> >
>> >
>> >
>> > in scheme, I have
>> >
>> > (let ((bar (get-foo))) [1]
>> >   [2] <-- how do I write this line in scheme?
>>
>> (if bar (do-something-with bar) (do-something-else))
>>
>>
>> (get-foo) should evaluate to #f if there is no bar.
>>
>> You should give #scheme a try for such basic questions.
>>
>> Good luck,
>>
>> Marijn
>>
>>
>> - --
>> Sarcasm puts the iron in irony, cynicism the steel.
>>
>> Marijn Schouten (hkBst), Gentoo Lisp project, Gentoo ML
>> <http://www.gentoo.org/proj/en/lisp/>, #gentoo-{lisp,ml} on FreeNode
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>
>
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