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* Updated doc for SCM_ASSERT.

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Neil Jerram 2001-04-16 09:38:32 +00:00
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@ -1,3 +1,9 @@
2001-04-16 Neil Jerram <neil@ossau.uklinux.net>
* data-rep.texi (Signalling Type Errors): Update SCM_ASSERT doc
for recent changes to disallow passing a string parameter as the
`pos'. Thanks to Dirk Herrmann for the patch!
2001-04-13 Neil Jerram <neil@ossau.uklinux.net>
* data-rep.texi (Unpacking the SCM type): New section, taken from

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@ -46,7 +46,7 @@
@c essay @sp 10
@c essay @comment The title is printed in a large font.
@c essay @title Data Representation in Guile
@c essay @subtitle $Id: data-rep.texi,v 1.20 2001-04-13 11:12:01 ossau Exp $
@c essay @subtitle $Id: data-rep.texi,v 1.21 2001-04-16 09:38:32 ossau Exp $
@c essay @subtitle For use with Guile @value{VERSION}
@c essay @author Jim Blandy
@c essay @author Free Software Foundation
@ -1021,15 +1021,10 @@ types of its arguments, to avoid misinterpreting a value, and perhaps
causing a segmentation fault. Guile provides some macros to make this
easier.
@deftypefn Macro void SCM_ASSERT (int @var{test}, SCM @var{obj}, int @var{position}, char *@var{subr})
If @var{test} is zero, signal an error, attributed to the subroutine
named @var{subr}, operating on the value @var{obj}. The @var{position}
value determines exactly what sort of error to signal.
If @var{position} is a string, @code{SCM_ASSERT} raises a
``miscellaneous'' error whose message is that string.
Otherwise, @var{position} should be one of the values defined below.
@deftypefn Macro void SCM_ASSERT (int @var{test}, SCM @var{obj}, unsigned int @var{position}, const char *@var{subr})
If @var{test} is zero, signal a ``wrong type argument'' error,
attributed to the subroutine named @var{subr}, operating on the value
@var{obj}, which is the @var{position}'th argument of @var{subr}.
@end deftypefn
@deftypefn Macro int SCM_ARG1
@ -1037,35 +1032,21 @@ Otherwise, @var{position} should be one of the values defined below.
@deftypefnx Macro int SCM_ARG3
@deftypefnx Macro int SCM_ARG4
@deftypefnx Macro int SCM_ARG5
Signal a ``wrong type argument'' error. When used as the @var{position}
argument of @code{SCM_ASSERT}, @code{SCM_ARG@var{n}} claims that
@var{obj} has the wrong type for the @var{n}'th argument of @var{subr}.
The only way to complain about the type of an argument after the fifth
is to use @code{SCM_ARGn}, defined below, which doesn't specify which
argument is wrong. You could pass your own error message to
@code{SCM_ASSERT} as the @var{position}, but then the error signalled is
a ``miscellaneous'' error, not a ``wrong type argument'' error. This
seems kludgy to me.
@comment Any function with more than two arguments is wrong --- Perlis
@comment Despite Perlis, I agree. Why not have two Macros, one with
@comment a string error message, and the other with an integer position
@comment that only claims a type error in an argument?
@comment --- Keith Wright
@deftypefnx Macro int SCM_ARG6
@deftypefnx Macro int SCM_ARG7
One of the above values can be used for @var{position} to indicate the
number of the argument of @var{subr} which is being checked.
Alternatively, a positive integer number can be used, which allows to
check arguments after the seventh. However, for parameter numbers up to
seven it is preferable to use @code{SCM_ARGN} instead of the
corresponding raw number, since it will make the code easier to
understand.
@end deftypefn
@deftypefn Macro int SCM_ARGn
As above, but does not specify which argument's type is incorrect.
@end deftypefn
@deftypefn Macro int SCM_WNA
Signal an error complaining that the function received the wrong number
of arguments.
Interestingly, the message is attributed to the function named by
@var{obj}, not @var{subr}, so @var{obj} must be a Scheme string object
naming the function. Usually, Guile catches these errors before ever
invoking the subr, so we don't run into these problems.
Passing a value of zero or @code{SCM_ARGn} for @var{position} allows to
leave it unspecified which argument's type is incorrect. Again,
@code{SCM_ARGn} should be preferred over a raw zero constant.
@end deftypefn