- easier support for non-mandatory functions.

  In some boundary conditions it can be desirable to support
  additional functions, but not necessarily require them. Make this
  easier to support with a Function1, PatchFunction1 NewIfPresent()
  selector.

- support for compatibility lookups

- harmonize branching logic and error handling between Function1 and
  PatchFunction1.

ENH: refactor a base class for Function1, PatchFunction1

- includes base characteristics, patch or scalar information

ENH: additional creation macros

- makeConcreteFunction1, makeConcretePatchFunction1Type for adding a
  non-templated function into the correct templated selection table.
  makeScalarPatchFunction1 for similarity with makeScalarFunction1

- reduce code duplication, support returning multiple interpolations
  as a Field

- makes the intent clearer and avoids the need for additional
  constructor casting. Eg,

      labelList(10, Zero)    vs.  labelList(10, 0)
      scalarField(10, Zero)  vs.  scalarField(10, scalar(0))
      vectorField(10, Zero)  vs.  vectorField(10, vector::zero)

- more dictionary-like methods, enforce keyType::LITERAL for all
  lookups to avoid any spurious keyword matching.

- new readEntry, readIfPresent methods

- The get() method replaces the now deprecate lookup() method.

- Deprecate lookupOrFailsafe()
  Failsafe behaviour is now an optional parameter for lookupOrDefault,
  which makes it easier to tailor behaviour at runtime.

- output of the names is now always flatted without line-breaks.
  Thus,

     os << flatOutput(someEnumNames.names()) << nl;
     os << someEnumNames << nl;

  both generate the same output.

- Constructor now uses C-string (const char*) directly instead of
  Foam::word in its initializer_list.

- Remove special enum + initializer_list constructor form since
  it can create unbounded lookup indices.

- Removd old hasEnum, hasName forms that were provided during initial
  transition from NamedEnum.

- Added static_assert on Enum contents to restrict to enum or
  integral values.  Should not likely be using this class to enumerate
  other things since it internally uses an 'int' for its values.

  Changed volumeType accordingly to enumerate on its type (enum),
  not the class itself.

Improve alignment of its behaviour with std::unique_ptr

  - element_type typedef
  - release() method - identical to ptr() method
  - get() method to get the pointer without checking and without releasing it.
  - operator*() for dereferencing

Method name changes

  - renamed rawPtr() to get()
  - renamed rawRef() to ref(), removed unused const version.

Removed methods/operators

  - assignment from a raw pointer was deleted (was rarely used).
    Can be convenient, but uncontrolled and potentially unsafe.
    Do allow assignment from a literal nullptr though, since this
    can never leak (and also corresponds to the unique_ptr API).

Additional methods

  - clone() method: forwards to the clone() method of the underlying
    data object with argument forwarding.

  - reset(autoPtr&&) as an alternative to operator=(autoPtr&&)

STYLE: avoid implicit conversion from autoPtr to object type in many places

- existing implementation has the following:

     operator const T&() const { return operator*(); }

  which means that the following code works:

       autoPtr<mapPolyMesh> map = ...;
       updateMesh(*map);    // OK: explicit dereferencing
       updateMesh(map());   // OK: explicit dereferencing
       updateMesh(map);     // OK: implicit dereferencing

  for clarity it may preferable to avoid the implicit dereferencing

- prefer operator* to operator() when deferenced a return value
  so it is clearer that a pointer is involve and not a function call
  etc    Eg,   return *meshPtr_;  vs.  return meshPtr_();

- makes for clearer code

ENH: make writeIfDifferent part of Ostream

- replace duplicate code with global bounds enums and Enum

Resolves bug-report http://bugs.openfoam.org/view.php?id=2356

This change requires that the de-reference operator '()' returns a
const-reference to the object stored irrespective of the const-ness of
object stored and the new member function 'ref()' is provided to return
an non-const reference to stored object which throws a fatal error if the
stored object is const.

In order to smooth the transition to this new safer 'tmp' the now
deprecated and unsafe non-const de-reference operator '()' is still
provided by default but may be switched-off with the compilation switch
'CONST_TMP'.

The main OpenFOAM library has already been upgraded and '-DCONST_TMP'
option specified in the 'options' file to switch to the new 'tmp'
behavior.  The rest of OpenFOAM-dev will be upgraded over the following
few weeks.

Henry G. Weller
CFD Direct

Function1 is an abstract base-class of run-time selectable unary
functions which may be composed of other Function1's allowing the user
to specify complex functions of a single scalar variable, e.g. time.
The implementations need not be a simple or continuous functions;
interpolated tables and polynomials are also supported.  In fact form of
mapping between a single scalar input and a single primitive type output
is supportable.

The primary application of Function1 is in time-varying boundary
conditions, it also used for other functions of time, e.g. injected mass
is spray simulations but is not limited to functions of time.

to avoid name conflicts with these primitive names in the OpenFOAM namespace

Removed inconsistent binary output.
Removed unused and IO-inconsistent functions.
Simplified the handling of backward-compatible constant value:
    Removed the unnecessary CompatibilityConstant,
    Updated Constant and DataEntryNew to handle constant value construction.

Avoids the clutter and maintenance effort associated with providing the
function signature string.

This resolves issues with and complexities in the virtual function inheritance