Function1::ramp: New set of scalar ramp functions

Description
    Ramp function base class for the set of scalar functions starting from 0 and
    increasing monotonically to 1 from \c start over the \c duration and
    remaining at 1 thereafter.

    Usage:
    \verbatim
        <entryName> <rampFunction>;
        <entryName>Coeffs
        {
            start     10;
            duration  20;
        }
    \endverbatim
    or
    \verbatim
        <entryName>
        {
            type      <rampFunction>;
            start     10;
            duration  20;
        }
    \endverbatim

    Where:
    \table
        Property | Description  | Required | Default value
        start    | Start time   | no       | 0
        duration | Duration     | yes      |
    \endtable

The following common ramp functions are provided: linear, quadratic, halfCosine,
quarterCosine and quaterSine, others can easily be added and registered to the run-time
selection system.

src/OpenFOAM/primitives/functions/Function1/ramp/ramp.H

@@ -0,0 +1,150 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2017 OpenFOAM Foundation
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Class
+    Foam::Function1Types::ramp
+
+Description
+    Ramp function base class for the set of scalar functions starting from 0 and
+    increasing monotonically to 1 from \c start over the \c duration and
+    remaining at 1 thereafter.
+
+    Usage:
+    \verbatim
+        <entryName> <rampFunction>;
+        <entryName>Coeffs
+        {
+            start     10;
+            duration  20;
+        }
+    \endverbatim
+    or
+    \verbatim
+        <entryName>
+        {
+            type      <rampFunction>;
+            start     10;
+            duration  20;
+        }
+    \endverbatim
+
+    Where:
+    \table
+        Property | Description  | Required | Default value
+        start    | Start time   | no       | 0
+        duration | Duration     | yes      |
+    \endtable
+
+See also
+    Foam::Function1
+
+SourceFiles
+    ramp.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef ramp_H
+#define ramp_H
+
+#include "Function1.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace Function1Types
+{
+
+/*---------------------------------------------------------------------------*\
+                           Class ramp Declaration
+\*---------------------------------------------------------------------------*/
+
+class ramp
+:
+    public Function1<scalar>
+{
+protected:
+
+    // Protected data
+
+        //- Start-time of the ramp function
+        scalar start_;
+
+        //- Duration of the ramp function
+        scalar duration_;
+
+        //- Simple linear ramp function
+        //  which form the basis of many more complex ramp functions
+        inline scalar linearRamp(const scalar t) const
+        {
+            return max(min((t - start_)/duration_, 1), 0);
+        }
+
+
+private:
+
+    // Private Member Functions
+
+        //- Read the coefficients from the given dictionary
+        void read(const dictionary& coeffs);
+
+        //- Disallow default bitwise assignment
+        void operator=(const ramp&);
+
+
+public:
+
+    // Constructors
+
+        //- Construct from entry name and dictionary
+        ramp
+        (
+            const word& entryName,
+            const dictionary& dict
+        );
+
+
+    //- Destructor
+    virtual ~ramp();
+
+
+    // Member Functions
+
+        //- Return value for time t
+        scalar value(const scalar t) const = 0;
+
+        //- Write in dictionary format
+        virtual void writeData(Ostream& os) const;
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace Function1Types
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //