From 6ed2b129cbd174f91b0d8bdf446542c852474bb9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A5rd=20Skaflestad?= <Bard.Skaflestad@sintef.no>
Date: Tue, 30 Apr 2013 13:41:13 +0200
Subject: [PATCH] Implement constant() and variable() in terms of function()

Specifically,

  - A constant is a function with zero derivative
  - A variable is a function with unit derivative with respect to
    itself.
---
 AutoDiff.hpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/AutoDiff.hpp b/AutoDiff.hpp
index aa19343c7..8a758c453 100644
--- a/AutoDiff.hpp
+++ b/AutoDiff.hpp
@@ -45,13 +45,15 @@ namespace AutoDiff {
         static Forward
         constant(const Scalar x)
         {
-            return Forward(x, Scalar(0));
+            // Constant is function with zero derivative.
+            return function(x, Scalar(0));
         }
 
         static Forward
         variable(const Scalar x)
         {
-            return Forward(x, Scalar(1));
+            // Variable is function with unit derivative (wrt. itself).
+            return function(x, Scalar(1));
         }
 
         static Forward