[common] Introduce integer range class

This class generates a IntRange [a,b) which can be used in a for loop, e.g

for(auto i : IntRange(3) { ... i = 0, 1, 2 }   or

for(auto i : IntRange(5, 8) { ... i = 5, 6, 7}

see: https://en.wikipedia.org/wiki/Generator_(computer_programming)

dumux/common/intrange.hh

+// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+// vi: set et ts=4 sw=4 sts=4:
+/*****************************************************************************
+ *   See the file COPYING for full copying permissions.                      *
+ *                                                                           *
+ *   This program 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 2 of the License, or       *
+ *   (at your option) any later version.                                     *
+ *                                                                           *
+ *   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.   *
+ *****************************************************************************/
+/*!
+ * \file
+ * \brief A class to create an iterable integer range
+ */
+#ifndef DUMUX_INTEGER_RANGE_HH
+#define DUMUX_INTEGER_RANGE_HH
+
+namespace Dumux
+{
+
+/*!
+ * \brief This class generates a IntRange [a,b) which can be used in a for loop, e.g.
+ *        for(auto i : IntRange(3) { ... i = 0, 1, 2 }   or
+ *        for(auto i : IntRange(5, 8) { ... i = 5, 6, 7 }
+ *        see: https://en.wikipedia.org/wiki/Generator_(computer_programming)
+ */
+class IntRange
+{
+public:
+    // constructors
+    IntRange(int end): last_(end), iter_(0) { assert(end > 0); }
+    IntRange(int begin, int end): last_(end), iter_(begin) { assert(end > begin); }
+    IntRange() = delete;
+
+    // Iterable functions
+     const IntRange& begin() const { return *this; }
+     const IntRange& end() const { return *this; }
+
+    // Iterator functions
+    bool operator!=(const IntRange&) const { return iter_ < last_; }
+    void operator++() { ++iter_; }
+    int operator*() const { return iter_; }
+private:
+    int last_;
+    int iter_;
+};
+
+} // namespace Dumux
+
+#endif