ENH: improve HashTable iterator access and management

- provide key_iterator/const_key_iterator for all hashes,
  reuse directly for HashSet as iterator/const_iterator, respectively.

- additional keys() method for HashTable that returns a wrapped to
  a pair of begin/end const_iterators with additional size/empty
  information that allows these to be used directly by anything else
  expecting things with begin/end/size. Unfortunately does not yet
  work with std::distance().

  Example,
     for (auto& k : labelHashTable.keys())
     {
        ...
     }

applications/test/HashSet/Test-hashSet.C

@@ -69,6 +69,12 @@ int main(int argc, char *argv[])
 
     Info<< "tableA keys: "; tableA.writeKeys(Info) << endl;
 
+    auto keyIterPair = tableA.keys();
+    for (const auto& i : keyIterPair)
+    {
+        Info<<" keys: " << i << endl;
+    }
+
     Map<label> mapA
     {
         { 1, 1 },
@@ -193,7 +199,7 @@ int main(int argc, char *argv[])
 
     Info<< "setD : " << flatOutput(setD) << endl;
 
-    // this doesn't work (yet?)
+    // This should not work (yet?)
     // setD[12] = true;
 
     List<label> someLst(10);

applications/test/HashTable/Test-hashTable.C

@@ -24,6 +24,7 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "HashTable.H"
+#include "List.H"
 #include "IOstreams.H"
 #include "IStringStream.H"
 #include "OStringStream.H"
@@ -177,12 +178,23 @@ int main()
 
     Info<< "\ntable1" << table1 << nl;
 
-    Info<< "\nrange-for(table1)" << nl;
-    for (auto const& it : table1)
+    Info<< "\nrange-for(table1) - returns values" << nl;
+    for (const auto& it : table1)
     {
-        Info<< " " << it << nl;
+        Info<< "val:" << it << nl;
     }
 
+    Info<< "\nrange-for(table1.keys()) - returns keys" << nl;
+    for (const auto& k : table1.keys())
+    {
+        Info<< "key:" << k << nl;
+    }
+
+    // These do not yet work. Issues resolving the distance.
+    //
+    //  List<scalar> table1vals(table1.begin(), table1.end());
+    //  wordList table1keys(table1.begin(), table1.end());
+
     Info<< "\nDone\n";
 
     return 0;

applications/test/cplusplus1/Make/files

@@ -0,0 +1,3 @@
+Test-cpluplus1.C
+
+EXE = $(FOAM_USER_APPBIN)/Test-cpluplus1

applications/test/cplusplus1/Make/options

@@ -0,0 +1,2 @@
+/* EXE_INC = -I$(LIB_SRC)/cfdTools/include */
+/* EXE_LIBS = -lfiniteVolume */

applications/test/cplusplus1/Test-cpluplus1.C

@@ -0,0 +1,88 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     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/>.
+
+Description
+    Test miscellaneous C++ templates/functionality.
+
+\*---------------------------------------------------------------------------*/
+
+#include "string.H"
+#include "IOstreams.H"
+#include "UList.H"
+#include "HashSet.H"
+
+#include <typeinfo>
+#include <type_traits>
+#include <utility>
+
+using namespace Foam;
+
+// Macros to stringify macro contents.
+#define STRINGIFY(content)      #content
+#define STRING_QUOTE(input)     STRINGIFY(input)
+
+#define PRINT_TYPEID(arg)       \
+    Info<< typeid(arg).name() << " <= typeid of " << STRING_QUOTE(arg) << nl
+
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+// Main program:
+
+int main(int argc, char *argv[])
+{
+    Info<< "various declaration types" << nl << nl;
+
+    PRINT_TYPEID(label);
+    PRINT_TYPEID(decltype(UList<label>::value_type()));
+    PRINT_TYPEID(decltype(std::declval<UList<label>>().cbegin()));
+    PRINT_TYPEID(decltype(*(std::declval<UList<label>>().cbegin())));
+    Info<< nl;
+
+    PRINT_TYPEID(decltype(HashTable<label>::key_type()));
+    PRINT_TYPEID(decltype(HashTable<label>::value_type()));
+    // Not yet: PRINT_TYPEID(decltype(HashTable<label>::mapped_type()));
+    PRINT_TYPEID(decltype(std::declval<HashTable<label>>().begin()));
+    PRINT_TYPEID(decltype(std::declval<const HashTable<label>>().begin()));
+    PRINT_TYPEID(decltype(*(std::declval<HashTable<label>>().begin())));
+    PRINT_TYPEID(decltype(*(std::declval<const HashTable<label>>().begin())));
+
+    PRINT_TYPEID(decltype(std::declval<const HashTable<label>>().keys()));
+    Info<< nl;
+
+    PRINT_TYPEID(decltype(HashSet<label>::key_type()));
+    PRINT_TYPEID(decltype(HashSet<label>::value_type()));
+    // Not yet: PRINT_TYPEID(decltype(HashSet<label>::mapped_type()));
+    PRINT_TYPEID(decltype(std::declval<HashSet<label>>().begin()));
+    PRINT_TYPEID(decltype(std::declval<const HashSet<label>>().begin()));
+    PRINT_TYPEID(decltype(*(std::declval<HashSet<label>>().begin())));
+    PRINT_TYPEID(decltype(*(std::declval<const HashSet<label>>().begin())));
+    Info<< nl;
+
+    Info << "\nEnd\n" << endl;
+
+    return 0;
+}
+
+
+// ************************************************************************* //

applications/test/pTraits/Test-pTraits.C

@@ -29,6 +29,9 @@ Description
 #include "pTraits.H"
 #include "vector.H"
 #include "tensor.H"
+#include "uLabel.H"
+
+#include <type_traits>
 
 using namespace Foam;
 
@@ -40,7 +43,10 @@ void printTraits()
 {
     Info<< pTraits<T>::typeName
         << ": zero=" << pTraits<T>::zero
-        << " one=" << pTraits<T>::one << endl;
+        << " one=" << pTraits<T>::one
+        << " integral=" << std::is_integral<T>::value
+        << " floating=" << std::is_floating_point<T>::value
+        << endl;
 }
 
 
@@ -80,6 +86,21 @@ int main()
     label def = label();
     Info<< "intialized primitive:"<< def << endl;
 
+    Info<< nl << "some interesting label limits:" << nl;
+    std::cout<< "sizeof = " << sizeof(label) << nl;
+    std::cout<< "min = " << pTraits<label>::min << nl;
+    std::cout<< "max = " << pTraits<label>::max << nl;
+    std::cout<< "umax = " << pTraits<uLabel>::max << nl;
+
+    std::cout<< "max_2 = " << pTraits<label>::max/2 << " == "
+        << (1 << (sizeof(label)*8-2)) << nl;
+
+    std::cout<< "max_4 = " << pTraits<label>::max/4 << " == "
+        << (1 << (sizeof(label)*8-3)) << nl;
+
+    std::cout<< "max_8 = " << pTraits<label>::max/8 << " == "
+        << (1 << (sizeof(label)*8-4)) << nl;
+
     Info<< "End\n" << endl;
 
     return 0;