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| -rw-r--r-- | doc/lispref/variables.texi | 12 | ||||
| -rw-r--r-- | doc/misc/cl.texi | 5 |
2 files changed, 17 insertions, 0 deletions
diff --git a/doc/lispref/variables.texi b/doc/lispref/variables.texi index a2d64815d94..ba31f856369 100644 --- a/doc/lispref/variables.texi +++ b/doc/lispref/variables.texi @@ -221,6 +221,18 @@ Here is an example of this: @code{z} is bound to the old value of @result{} (1 2) @end group @end example + +On the other hand, the order of @emph{bindings} is unspecified: in the +following example, either 1 or 2 might be printed. + +@example +(let ((x 1) + (x 2)) + (print x)) +@end example + +Therefore, avoid binding a variable more than once in a single +@code{let} form. @end defspec @defspec let* (bindings@dots{}) forms@dots{} diff --git a/doc/misc/cl.texi b/doc/misc/cl.texi index c62fa727c10..75a83602fa3 100644 --- a/doc/misc/cl.texi +++ b/doc/misc/cl.texi @@ -1179,6 +1179,11 @@ behavior. (@code{point} and @code{point-marker} are equivalent as @code{setf} places; each will accept either an integer or a marker as the stored value.) +Like in the case of @code{let}, the @var{value} forms are evaluated in +the order they appear, but the order of bindings is unspecified. +Therefore, avoid binding the same @var{place} more than once in a +single @code{cl-letf} form. + Since generalized variables look like lists, @code{let}'s shorthand of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would be ambiguous in @code{cl-letf} and is not allowed. |