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- Documented multiple return values from ffi:c-inline.

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japhie 2005-05-21 10:29:30 +00:00
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34
src/doc/devel.txi
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@ -1439,22 +1439,26 @@ to the Lisp world, with an automatic convertion taking place in both directions.
@defmac {c-inline} @{@var{args-list} @var{arg-C-types} @var{output-C-type} @var{C-expr} @keys{} (@var{side-effects} @code{T}) (@var{one-liner} @code{T})@}
@code{c-inline} is a special form that can only be used in compiled code.
For all purposes it behaves as a Lisp form, which takes the arguments
given in @var{args-list} and produces a single value. Behind the curtains,
the arguments of @var{args-list} (which can be any valid Lisp form)
are coerced to the the C types given in @var{arg-C-types}, passed to
the C expression @var{C-expr}, and coerced back to Lisp using the
C type @var{output-C-type} as a guide.
@code{c-inline} is a special form that can only be used in compiled
code. For all purposes it behaves as a Lisp form, which takes the
arguments given in @var{args-list} and produces a single value. Behind
the curtains, the arguments of @var{args-list} (which can be any valid
Lisp form) are coerced to the the C types given in @var{arg-C-types},
passed to the C expression @var{C-expr}, and coerced back to Lisp
using the C type @var{output-C-type} as a guide. Multiple return
values can be returned by setting @var{output-C-type} to @code{(values
type-1 type-2 ...)}.
@var{C-expr} is a string containing C code and maybe some special escape codes.
First, the arguments of the form may be retrieved as @code{#0}, @code{#1}, etc.
Second, if the @code{c-inline} form is a one-line C expression (That is,
@var{one-liner} is true), then the whole expression is interpreted as the
output value. But if the code, on the other hand, is a multiline expression
(@var{one-liner} is false), the form has to be output using @code{@@(return)
=...}. Finally, Lisp constants may be used in the C code making use of the
prefix @code{@@}.
@var{C-expr} is a string containing C code and maybe some special
escape codes. First, the arguments of the form may be retrieved as
@code{#0}, @code{#1}, etc. Second, if the @code{c-inline} form is a
one-line C expression (That is, @var{one-liner} is true), then the
whole expression is interpreted as the output value. But if the code,
on the other hand, is a multiline expression (@var{one-liner} is
false), the form has to be output using @code{@@(return)
=...}. Multiple values are returned as @code{@@(return 0)=... ;
@@(return 1)=...;}. Finally, Lisp constants may be used in the C code
making use of the prefix @code{@@}.
@example
(use-package "FFI")