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Lib/Include/CML/et/traits.h

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+/* -*- C++ -*- ------------------------------------------------------------
+ 
+Copyright (c) 2007 Jesse Anders and Demian Nave http://cmldev.net/
+
+The Configurable Math Library (CML) is distributed under the terms of the
+Boost Software License, v1.0 (see cml/LICENSE for details).
+
+ *-----------------------------------------------------------------------*/
+/** @file
+ *  @brief
+ */
+
+#ifndef traits_h
+#define traits_h
+
+#include <cml/et/tags.h>
+
+/* XXX This is here temporarily, should be rolled into the traits classes
+ * once it's clear how to best specify scalar args
+ */
+//#define SCALAR_ARG_TYPE const ScalarT&
+//#define ELEMENT_ARG_TYPE const Element&
+#define SCALAR_ARG_TYPE ScalarT
+#define ELEMENT_ARG_TYPE Element
+
+namespace cml {
+namespace et {
+
+/** The expression traits class.
+ *
+ * The traits class is used to provide uniform access to expression
+ * objects, including scalars, when used in vector and matrix expressions.
+ * One especially useful property for scalars is that scalars are
+ * implicitly "promoted" to vectors or scalars as necessary via the
+ * ExprTraits's get() method.  Without this functionality, a separate
+ * expression tree node would be needed to hold a scalar, which would
+ * adversely affect performance.
+ *
+ * @internal This is also currently used for determining traits of scalar
+ * types from the scalar operators (+,-,etc.).  Really, a separate traits
+ * class should probably be used for this (e.g. ScalarTraits).
+ */
+template<typename T> struct ExprTraits
+#if defined(CML_NO_DEFAULT_EXPR_TRAITS)
+/* For testing, don't default to scalar traits: */
+#else
+{
+    /* Standard: */
+    typedef T expr_type;
+    typedef T value_type;
+    typedef T& reference;
+    typedef T const_reference;
+    typedef scalar_result_tag result_tag;
+    typedef fixed_memory_tag memory_tag;
+    typedef unit_size_tag size_tag;
+    typedef expr_type result_type;
+    typedef expr_leaf_tag node_tag;
+
+    /** Vector-like access, just returns the value. */
+    value_type get(const_reference v, size_t) const { return v; }
+
+    /** Matrix-like access, just returns the value. */
+    value_type get(const_reference v, size_t, size_t) const { return v; }
+
+    /** Size is always 1. */
+    size_t size(const_reference) const { return 1; }
+
+    /** Size is always 1. */
+    size_t rows(double) const { return 1; }
+
+    /** Size is always 1. */
+    size_t cols(double) const { return 1; }
+}
+#endif
+;
+
+#if defined(CML_NO_DEFAULT_EXPR_TRAITS)
+template<> struct ExprTraits<double>
+{
+    /* Standard: */
+    typedef double expr_type;
+    typedef double value_type;
+    typedef double& reference;
+    typedef double const_reference;
+    typedef scalar_result_tag result_tag;
+    typedef fixed_memory_tag memory_tag;
+    typedef unit_size_tag size_tag;
+    typedef double result_type;
+    typedef expr_leaf_tag node_tag;
+
+    /** Vector-like access, just returns the value. */
+    value_type get(double v, size_t) const { return v; }
+
+    /** Matrix-like access, just returns the value. */
+    value_type get(double v, size_t, size_t) const { return v; }
+
+    /** Size is always 1. */
+    size_t size(double) const { return 1; }
+
+    /** Size is always 1. */
+    size_t rows(double) const { return 1; }
+
+    /** Size is always 1. */
+    size_t cols(double) const { return 1; }
+};
+
+template<> struct ExprTraits<float>
+{
+    /* Standard: */
+    typedef float expr_type;
+    typedef float value_type;
+    typedef float& reference;
+    typedef float const_reference;
+    typedef scalar_result_tag result_tag;
+    typedef fixed_memory_tag memory_tag;
+    typedef unit_size_tag size_tag;
+    typedef float result_type;
+    typedef expr_leaf_tag node_tag;
+
+    /** Vector-like access, just returns the value. */
+    value_type get(float v, size_t) const { return v; }
+
+    /** Matrix-like access, just returns the value. */
+    value_type get(float v, size_t, size_t) const { return v; }
+
+    /** Size is always 1. */
+    size_t size(float) const { return 1; }
+
+    /** Size is always 1. */
+    size_t rows(float) const { return 1; }
+
+    /** Size is always 1. */
+    size_t cols(float) const { return 1; }
+};
+#endif
+
+} // namespace et
+} // namespace cml
+
+#endif
+
+// -------------------------------------------------------------------------
+// vim:ft=cpp