* match.c (do_txeval): Lift an annoying restriction in the pattern

language's expression evaluator. Whereas TXR Lisp expressions can be
used int the pattern language, preceded by @, it was not possible
to evaluate TXR Lisp variables this way. So instead of @var,
some clumsy trick had to be used like @(identity var). This is not
necessary any more. Code like @(next @*stdin*) will now work.

* txr.1: Updated.

3 files changed, 20 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index 5bdc3375..f5cf8026 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+014-01-10  Kaz Kylheku  <kaz@kylheku.com>
+
+	* match.c (do_txeval): Lift an annoying restriction in the pattern
+	language's expression evaluator. Whereas TXR Lisp expressions can be
+	used int the pattern language, preceded by @, it was not possible
+	to evaluate TXR Lisp variables this way. So instead of @var,
+	some clumsy trick had to be used like @(identity var). This is not
+	necessary any more. Code like @(next @*stdin*) will now work.
+
+	* txr.1: Updated.
+
 2014-01-10  Kaz Kylheku  <kaz@kylheku.com>
 
 	* configure: Generate HAVE_VALGRIND as #define-d to 1, rathern
diff --git a/match.c b/match.c
index 23e96e9e..d46eced7 100644
--- a/match.c
+++ b/match.c
@@ -1432,8 +1432,10 @@ static val do_txeval(val spec, val form, val bindings, val allow_unbound)
       } else if (regexp(car(form))) {
         ret = form;
       } else if (first(form) == var_s) {
-        sem_error(spec, lit("metavariable @~s syntax cannot be used here"),
-                  second(form), nao);
+        uw_env_begin;
+        uw_set_match_context(cons(spec, bindings));
+        ret = eval(second(form), make_env(bindings, nil, nil), form);
+        uw_env_end;
       } else if (first(form) == expr_s) {
         uw_env_begin;
         uw_set_match_context(cons(spec, bindings));
diff --git a/txr.1 b/txr.1
index b93da15e..587e67e0 100644
--- a/txr.1
+++ b/txr.1
@@ -4763,7 +4763,7 @@ The TXR language contains an embedded Lisp dialect called TXR Lisp.
 
 This language is exposed in TXR in three ways.
 
-Firstly, in any situation that calls for an expression, a Lisp compound
+Firstly, in any situation that calls for an expression, a Lisp 
 expression can be used, if it is preceded by the @ symbol. The Lisp expression
 is evaluated and its value  becomes the value of that expression.
 Thus, TXR directives are embedded in literal text using @, and Lisp expressions
@@ -4785,6 +4785,10 @@ Bind variable a to the integer 4:
 
   @(bind a @(+ 2 2))
 
+Bind variable b to the standard input stream:
+
+  @(bind a @*stdin*)
+
 Define several Lisp functions using @(do):
 
 @(do