ENH: added foamCalc (applications/tools)

Many possibilities:
- use as a simple calculator with vectors, tensors etc.
- test validity of expression syntax

As a calculator:

    foamCalc  '(vector(1,2,3) ^ vector(4,5,6)) * sqrt(34)'

The same, but with debugging:

    foamCalc -debug-switch fieldExpr=6 \
        'mag((vector(1,2,3) ^ vector(4,5,6))) * sqrt(34)'

applications/tools/foamCalc/Make/files

+foamCalc.C
+
+EXE = $(FOAM_APPBIN)/foamCalc

applications/tools/foamCalc/Make/options

+/* EXE_INC = */
+/* EXE_LIBS = */

applications/tools/foamCalc/foamCalc.C

+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2019 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+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/>.
+
+Application
+    foamCalc
+
+Group
+    grpTools
+
+Description
+    A simple expression calculator using OpenFOAM string evaluation.
+    Multiple arguments will be concatenated together.
+
+Usage
+    \b foamCalc [OPTION]
+
+    Options:
+      - \par -precision int
+        Output with specified precision
+
+      - \par -rules
+        Print parser rules and exit
+
+      - \par -tokens
+        Print token names  and exit
+
+\*---------------------------------------------------------------------------*/
+
+#include "argList.H"
+#include "IOstreams.H"
+#include "exprString.H"
+#include "stringOps.H"
+#include "fieldExprParser.H"
+
+using namespace Foam;
+
+template<class Parser>
+void printInformation
+(
+    Ostream& os,
+    const word& name,
+    const bool printNames,
+    const bool printRules
+)
+{
+    if (printNames)
+    {
+        os << nl << "# Tokens for " << name << nl;
+        Parser::printTokenNames(os);
+    }
+
+    if (printRules)
+    {
+        os << nl << "# Rules for " << name << nl;
+        Parser::printRules(os);
+    }
+}
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+// Main program:
+
+int main(int argc, char *argv[])
+{
+    argList::noBanner();
+    argList::noParallel();
+    argList::setAdvanced("case");  // Hide -case : has no meaning here
+
+    argList::addNote
+    (
+        "A simple expression calculator using OpenFOAM string evaluation.\n"
+        "Multiple arguments will be concatenated together."
+    );
+
+    argList::addBoolOption("rules", "Print parser rules and exit");
+    argList::addBoolOption("tokens", "Print token names and exit");
+    argList::addOption("precision", "int", "Output with specified precision");
+
+    // Flag arguments as optional so that -rules and -tokens works
+    argList::noMandatoryArgs();
+    argList::addArgument
+    (
+        "expression",
+        "The expression to evaluate"
+    );
+
+    argList args(argc, argv);
+
+    const bool printRules = args.found("rules");
+    const bool printNames = args.found("tokens");
+
+    if (printNames || printRules)
+    {
+        printInformation<expressions::fieldExpr::parser>
+        (
+            Info,
+            "field",
+            printNames,
+            printRules
+        );
+
+        return 0;
+    }
+
+    {
+        const int prec = args.lookupOrDefault<int>("precision", 0u);
+        if (prec > 0)
+        {
+            IOstream::defaultPrecision(prec);
+            Sout.precision(prec);
+        }
+    }
+
+    std::string expr;
+
+    for (int argi=1; argi < args.size(); ++argi)
+    {
+        if (argi > 1) expr += ' ';
+        expr += args[argi];
+    }
+
+    // Don't bother stripping C/C++, but do allow empty variables
+    stringOps::inplaceExpand(expr, true);
+    stringOps::inplaceTrim(expr);
+
+    if (expr.empty())
+    {
+        InfoErr
+            << "Error: no expression specified." << nl
+            << "See '" << args.executable() << " -help' for usage" << nl
+            << nl;
+
+        return 1;
+    }
+
+    Info<< stringOps::evaluate(expr).c_str() << nl;
+
+    return 0;
+}
+
+
+// ************************************************************************* //