Experimental first draft of 'functors' header.

src/functors.h

@@ -0,0 +1,145 @@
+///\file
+
+/******************************************************************************
+The MIT License(MIT)
+
+Embedded Template Library.
+https://github.com/ETLCPP/etl
+http://www.etlcpp.com
+
+Copyright(c) 2017 jwellbelove
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files(the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions :
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+******************************************************************************/
+
+#ifndef __ETL_FUNCTORS__
+#define __ETL_FUNCTORS__
+
+///\defgroup functors functors
+/// A set of functors for use with for_each
+///\ingroup utilities
+
+#include "type_traits.h"
+#include "static_assert.h"
+
+namespace etl
+{
+  //***************************************************************************
+  /// Finds the mean
+  ///\ingroup algorithm
+  //***************************************************************************
+  template <typename TSum, typename TCount = size_t>
+  class mean
+  {
+  public:
+
+    mean()
+      : sum(TSum()),
+        count(0)
+    {
+    }
+
+    mean(TSum initial_value)
+      : sum(initial_value()),
+        count(0)
+    {
+    }
+
+    template <typename TValue>
+    void operator()(TValue value)
+    {
+      sum += value;
+      ++count;
+    }
+
+    template <typename TResult>
+    typename etl::enable_if<etl::is_floating_point<TResult>::value, TResult>::type
+     result() const
+    {
+      return TResult(sum) / TResult(count);
+    }
+
+    template <typename TResult>
+    typename etl::enable_if<!etl::is_floating_point<TResult>::value, TResult>::type
+     result() const
+    {
+      return TResult(sum / count);
+    }
+
+    void reset()
+    {
+      sum   = TSum();
+      count = 0;
+    }
+
+  private:
+
+    TSum   sum;
+    TCount count;
+  };
+
+  //***************************************************************************
+  /// Finds the mean on a rolling basis.
+  /// Defaults to an initial value of TMean() and a ratio of 0.1
+  ///\ingroup algorithm
+  //***************************************************************************
+  template <typename TMean, typename TRatio = double>
+  class rolling_mean
+  {
+  public:
+
+    STATIC_ASSERT(etl::is_floating_point<TRatio>::value, "TRatio must be a floating point type");
+
+    rolling_mean(TMean  initial_value = TMean(),
+                 TRatio ratio_        = TRatio(0.1)
+      : mean(initial_value),
+        ratio(ratio_)
+    {
+    }
+
+    template <typename TValue>
+    void operator()(TValue value)
+    {
+      mean -= (mean * ratio);
+      mean += (value * ratio);
+    }
+
+    void set_ratio(TRatio ratio_)
+    {
+      ratio = ratio_;
+    }
+
+    TMean result() const
+    {
+      return mean;
+    }
+
+    void reset()
+    {
+      mean = TMean();
+    }
+
+  private:
+
+    TMean mean;
+  };
+}
+
+#endif
+