[PATCH 1 of 4] Add identity_val and conj_val functor objects to functor.h

[Jason Riedy]

# HG changeset patch
# User Jason Riedy <jason at acm.org>
# Date 1236635352 14400
# Node ID 8ec69bd63c7360d9b186677968a5f93038c8c899
# Parent  42e24f4ebc8c70db07d0fcfd08d70b7a40e5519c
Add identity_val and conj_val functor objects to functor.h.

>From 059be213f0d43ff6f5874b689357119961b9dce7 Mon Sep 17 00:00:00 2001
Date: Sun, 8 Mar 2009 16:12:49 -0400
This is a stop-gap.  Both of these are unnecessary given features in
the upcoming C++ revision, but wide implementation is some distance
off.  Note that both are in an octave_impl namespace to avoid rampant
pollution.  Namespaces are widely enough supported now.

Signed-off-by: Jason Riedy <jason at acm.org>
---
 liboctave/ChangeLog |   12 ++++++++++++
 liboctave/functor.h |   22 ++++++++++++++++++++++
 2 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/liboctave/ChangeLog b/liboctave/ChangeLog
--- a/liboctave/ChangeLog
+++ b/liboctave/ChangeLog
@@ -1,3 +1,15 @@
+2009-03-08  Jason Riedy  <jason at acm.org>
+
+	* functor.h (octave_impl::identity_val): New function object.
+	Takes a value and returns that value.  Should eventually be
+	replaced by standard C++ functor, but those are in newer standards
+	versions.
+	(octave_impl::conj_val): New function object.  Takes a value and
+	returns its conjugate.  Imports std::conj rather than calling it
+	directly to allow non-standard types to pull in their own conj.
+	Again, this should be replaced by fancier functionality using
+	future C++ features eventually.
+
 2009-03-08  Jaroslav Hajek  <highegg at gmail.com>
 
 	* idx-vector.h (idx_vector::bloop): loop --> bloop.
diff --git a/liboctave/functor.h b/liboctave/functor.h
--- a/liboctave/functor.h
+++ b/liboctave/functor.h
@@ -72,6 +72,28 @@
   return functor_with_conversion<CT, RT, PT> (f);
 }
 
+namespace octave_impl {
+
+template <typename T> 
+struct identity_val
+  : public std::unary_function <T, T>
+{
+  T operator () (const T x) { return x; }
+};
+
+template <typename T> 
+struct conj_val
+  : public std::unary_function <T, T>
+{
+  T operator () (const T x)
+    {
+      using std::conj;
+      return conj (x);
+    }
+};
+
+} // namespace octave_impl
+
 #endif
 
 /*