From 56da0c3895ae502a6e17064a8e3ad588694ae910 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Mon, 14 Mar 2016 22:00:51 -0700
Subject: @(output)_destination can be a stream.

* match.c (complex_open): If name is a stream object, just
return it.
(v_output): Do not close the output stream if it came
from a destination expression specifying an existing
stream, and thus wasn't created inside complex_open.

* txr.1: Document stream destination in output directive.
---
 match.c | 46 +++++++++++++++++++++++++---------------------
 txr.1   | 18 ++++++++++++------
 2 files changed, 37 insertions(+), 27 deletions(-)

diff --git a/match.c b/match.c
index b3684180..4fbac813 100644
--- a/match.c
+++ b/match.c
@@ -1538,33 +1538,37 @@ static val txeval_allow_ub(val spec, val form, val bindings)
 
 static val complex_open(val name, val output, val append, val nothrow)
 {
-  val fc = car(name);
-  val result = nil;
+  if (streamp(name)) {
+    return name;
+  } else {
+    val fc = car(name);
+    val result = nil;
 
-  if (fc == chr('$') && output)
-    uw_throwf(query_error_s, lit("cannot output to directory: ~a"),
-              name, nao);
+    if (fc == chr('$') && output)
+      uw_throwf(query_error_s, lit("cannot output to directory: ~a"),
+                name, nao);
 
-  uw_catch_begin (if2(nothrow, cons(error_s, nil)), exc_sym, exc);
+    uw_catch_begin (if2(nothrow, cons(error_s, nil)), exc_sym, exc);
 
-  if (fc == chr('-')) {
-    result = output ? std_output : std_input;
-  } else if (fc == chr('!')) {
-    result = open_command(cdr(name), output ? lit("w") : lit("r"));
-  } else if (fc == chr('$')) {
-    result = open_directory(cdr(name));
-  } else {
-    result = open_file(name,
-                       output ? append ? lit("a") : lit("w") : lit("r"));
-  }
+    if (fc == chr('-')) {
+      result = output ? std_output : std_input;
+    } else if (fc == chr('!')) {
+      result = open_command(cdr(name), output ? lit("w") : lit("r"));
+    } else if (fc == chr('$')) {
+      result = open_directory(cdr(name));
+    } else {
+      result = open_file(name,
+                         output ? append ? lit("a") : lit("w") : lit("r"));
+    }
 
-  uw_catch (exc_sym, exc) { (void) exc; }
+    uw_catch (exc_sym, exc) { (void) exc; }
 
-  uw_unwind { }
+    uw_unwind { }
 
-  uw_catch_end;
+    uw_catch_end;
 
-  return result;
+    return result;
+  }
 }
 
 static val robust_length(val obj)
@@ -3245,7 +3249,7 @@ static val v_output(match_files_ctx *c)
 
     if (named_var)
       c->bindings = acons(named_var, stream, c->bindings);
-    else
+    else if (!streamp(dest))
       close_stream(stream, t);
   }
 
diff --git a/txr.1 b/txr.1
index a6dc6d76..5508d7e5 100644
--- a/txr.1
+++ b/txr.1
@@ -7231,18 +7231,24 @@ directive is:
   @(end)
 .cble
 
-The optional
-.meta destination
-is a string which gives the path name of
+If the directive has arguments, then the first one is evaluated.
+If it is an object other than a keyword symbol, then it specifies
+the optional
+.metn destination .
+Any remaining arguments after the optional destination are
+the keyword list. If the destination is missing, then the
+entire argument list is a keyword list.
+
+The destination may be a string which gives the path name of
 a file to open for output. If the name is
 .code -
 it instead denotes standard output, and if it begins with
 .code !
 then the rest of the shell is treated as a shell command
-to which the output is piped.
+to which the output is piped.  The destination string may be specified as a
+variable which holds text, as a string literal or as a quasiliteral
 
-The destination may be specified as a variable
-which holds text, as a string literal or as a quasiliteral
+Alternatively, the destination may be a stream object.
 
 The keyword list consists of a mixture of boolean keywords which
 do not have an argument, or keywords with arguments.
-- 
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