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-rw-r--r--doc/ref/libguile-program.texi13
1 files changed, 6 insertions, 7 deletions
diff --git a/doc/ref/libguile-program.texi b/doc/ref/libguile-program.texi
index 2c30d246e..f565b916f 100644
--- a/doc/ref/libguile-program.texi
+++ b/doc/ref/libguile-program.texi
@@ -279,13 +279,12 @@ As an example, here is a possible implementation of the @code{square?}
primitive:
@lisp
-#define FUNC_NAME "square?"
static SCM square_p (SCM shape)
@{
struct dia_guile_shape * guile_shape;
/* Check that arg is really a shape SMOB. */
- SCM_VALIDATE_SHAPE (SCM_ARG1, shape);
+ scm_assert_smob_type (shape_tag, shape);
/* Access Scheme-specific shape structure. */
guile_shape = SCM_SMOB_DATA (shape);
@@ -295,7 +294,6 @@ static SCM square_p (SCM shape)
return scm_from_bool (guile_shape->c_shape &&
(guile_shape->c_shape->type == DIA_SQUARE));
@}
-#undef FUNC_NAME
@end lisp
Notice how easy it is to chain through from the @code{SCM shape}
@@ -303,10 +301,11 @@ parameter that @code{square_p} receives --- which is a SMOB --- to the
Scheme-specific structure inside the SMOB, and thence to the underlying
C structure for the shape.
-In this code, @code{SCM_SMOB_DATA} and @code{scm_from_bool} are from
-the standard Guile API. @code{SCM_VALIDATE_SHAPE} is a macro that you
-should define as part of your SMOB definition: it checks that the
-passed parameter is of the expected type. This is needed to guard
+In this code, @code{scm_assert_smob_type}, @code{SCM_SMOB_DATA}, and
+@code{scm_from_bool} are from the standard Guile API. We assume that
+@code{shape_tag} was given to us when we made the shape SMOB type, using
+@code{scm_make_smob_type}. The call to @code{scm_assert_smob_type}
+ensures that @var{shape} is indeed a shape. This is needed to guard
against Scheme code using the @code{square?} procedure incorrectly, as
in @code{(square? "hello")}; Scheme's latent typing means that usage
errors like this must be caught at run time.