Fix missing arg in pcase example.

* doc/lispref/control.texi (Pattern matching case statement): Fix missing
argument in simple expression language sample.  Add
some sample programs written in that language.  Mention that
`pcase' requires lexical binding.

Fixes: debbugs:16238

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index bee08a5..b1c2108 100644 (file)
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,10 @@
+2013-12-24  Tassilo Horn  <tsdh@gnu.org>
+
+       * control.texi (Pattern matching case statement): Fix missing
+       argument in simple expression language sample (Bug#16238).  Add
+       some sample programs written in that language.  Mention that
+       `pcase' requires lexical binding.
+
 2013-12-23  Xue Fuqiao  <xfq.free@gmail.com>
 
        * eval.texi (Special Forms): Document `special-form-p'.

diff --git a/doc/lispref/control.texi b/doc/lispref/control.texi
index 34a02aa..a9e7236 100644 (file)
--- a/doc/lispref/control.texi
+++ b/doc/lispref/control.texi
@@ -328,7 +328,7 @@ expression language could look like:
 (defun evaluate (exp env)
   (pcase exp
     (`(add ,x ,y)         (+ (evaluate x env) (evaluate y env)))
-    (`(call ,fun ,arg)    (funcall (evaluate fun) (evaluate arg env)))
+    (`(call ,fun ,arg)    (funcall (evaluate fun env) (evaluate arg env)))
     (`(fn ,arg ,body)     (lambda (val)
                             (evaluate body (cons (cons arg val) env))))
     ((pred numberp)       exp)
@@ -342,6 +342,19 @@ third elements and binds them to the variables @code{x} and @code{y}.
 @code{(pred numberp)} is a pattern that simply checks that @code{exp}
 is a number, and @code{_} is the catch-all pattern that matches anything.
 
+Here are some sample programs including their evaluation results:
+
+@example
+(evaluate '(add 1 2) nil)                 ;=> 3
+(evaluate '(add x y) '((x . 1) (y . 2)))  ;=> 3
+(evaluate '(call (fn x (add 1 x)) 2) nil) ;=> 3
+(evaluate '(sub 1 2) nil)                 ;=> (error "Unknown expression (sub 1 2)")
+@end example
+
+Note that (parts of) @code{pcase} only work as expected with lexical
+binding, so lisp files using @code{pcase} should have enable it
+(@pxref{Using Lexical Binding}, for how to enable lexical binding).
+
 There are two kinds of patterns involved in @code{pcase}, called
 @emph{U-patterns} and @emph{Q-patterns}.  The @var{upattern} mentioned above
 are U-patterns and can take the following forms: