STYLE: logical ops return bool (issue #1043)

- these currently only with bool parameters, but the return value should
  nonetheless always be a bool value:

      andOp(), orOp(), lessOp(), lessEqOp(), greaterOp(), greaterEqOp()

- renamed the unused eqEqOp() to equalOp() for naming consistency with
  the equal() global function.

ENH: equalOp() specialization for scalars

- function object version of the equal() function.
  The default constructor uses the same tolerance (VSMALL),
  but can also supply an alternative tolerance on construction.

applications/test/hexRef8/Test-hexRef8.C

@@ -48,12 +48,6 @@ using namespace Foam;
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-bool notEqual(const scalar s1, const scalar s2, const scalar tol)
-{
-    return mag(s1-s2) > tol;
-}
-
-
 // Main program:
 int main(int argc, char *argv[])
 {
@@ -180,6 +174,8 @@ int main(int argc, char *argv[])
     // Construct refiner. Read initial cell and point levels.
     hexRef8 meshCutter(mesh);
 
+    // Comparison for inequality
+    const auto isNotEqual = notEqualOp<scalar>(1e-10);
 
     while (runTime.loop())
     {
@@ -345,7 +341,7 @@ int main(int argc, char *argv[])
             Info<< "Uniform one field min = " << min
                 << "  max = " << max << endl;
 
-            if (notEqual(max, 1.0, 1e-10) || notEqual(min, 1.0, 1e-10))
+            if (isNotEqual(min, 1) || isNotEqual(max, 1))
             {
                 FatalErrorInFunction
                     << "Uniform volVectorField not preserved."
@@ -369,7 +365,7 @@ int main(int argc, char *argv[])
             Info<< "Linear profile field min = " << min
                 << "  max = " << max << endl;
 
-            if (notEqual(max, 0.0, 1e-10) || notEqual(min, 0.0, 1e-10))
+            if (isNotEqual(min, 0) || isNotEqual(max, 0))
             {
                 Info<< "Linear profile not preserved."
                     << " Min and max should both be 0.0. min:" << min
@@ -390,7 +386,7 @@ int main(int argc, char *argv[])
             Info<< "Uniform surface field min = " << min
                 << "  max = " << max << endl;
 
-            if (notEqual(max, 1.0, 1e-10) || notEqual(min, 1.0, 1e-10))
+            if (isNotEqual(min, 1) || isNotEqual(max, 1))
             {
                 FatalErrorInFunction
                     << "Uniform surfaceScalarField not preserved."

src/OpenFOAM/primitives/Scalar/Scalar.H

@@ -39,7 +39,7 @@ namespace Foam
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-// template specialisation for pTraits<Scalar>
+// Template specialisation for pTraits<Scalar>
 template<>
 class pTraits<Scalar>
 {
@@ -403,6 +403,52 @@ inline Scalar stabilise(const Scalar s, const Scalar tol)
 }
 
 
+// Specializations
+
+// Default definition in ops.H
+template<class T> struct equalOp;
+
+//- Compare scalar values for equality
+template<>
+struct equalOp<Scalar>
+{
+    const Scalar tolerance;
+
+    //- Construct with specified tolerance (non-negative value)
+    equalOp(Scalar tol = ScalarVSMALL)
+    :
+        tolerance(tol)
+    {}
+
+    bool operator()(const Scalar& a, const Scalar& b) const
+    {
+        return Foam::mag(a - b) <= tolerance;
+    }
+};
+
+
+// Default definition in ops.H
+template<class T> struct notEqualOp;
+
+//- Compare scalar values for inequality
+template<>
+struct notEqualOp<Scalar>
+{
+    const Scalar tolerance;
+
+    //- Construct with specified tolerance (non-negative value)
+    notEqualOp(Scalar tol = ScalarVSMALL)
+    :
+        tolerance(tol)
+    {}
+
+    bool operator()(const Scalar& a, const Scalar& b) const
+    {
+        return Foam::mag(a - b) > tolerance;
+    }
+};
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 } // End namespace Foam

src/OpenFOAM/primitives/ops/ops.H

@@ -25,12 +25,9 @@ InNamespace
     Foam
 
 Description
-    Various binary and unary operations, which can be used for example,
+    Various function objects for unary and binary operations.
-    for parallel combine-reduce operations.
+    Can be used for parallel combine-reduce operations or other places
-
+    requiring a function object.
-    The information from all nodes is collected on the master node,
-    combined using the given combination function and the result is
-    broadcast to all nodes
 
 \*---------------------------------------------------------------------------*/
 
@@ -134,9 +131,32 @@ EqOp(nopEq, (void)x)
     };
 
 
-// ...
+// Operations taking two parameters (unaltered), returning bool
 
-#define weightedOp(opName, op)                                                 \
+#define BoolOp(opName, op)                                                     \
+                                                                               \
+    template<class T1, class T2>                                               \
+    struct opName##Op2                                                         \
+    {                                                                          \
+        bool operator()(const T1& x, const T2& y) const WARNRETURN             \
+        {                                                                      \
+            return op;                                                         \
+        }                                                                      \
+    };                                                                         \
+                                                                               \
+    template<class T>                                                          \
+    struct opName##Op                                                          \
+    {                                                                          \
+        bool operator()(const T& x, const T& y) const WARNRETURN               \
+        {                                                                      \
+            return op;                                                         \
+        }                                                                      \
+    };
+
+
+// Weighting operations
+
+#define WeightedOp(opName, op)                                                 \
                                                                                \
     template<class T, class CombineOp>                                         \
     class opName##WeightedOp                                                   \
@@ -178,18 +198,21 @@ Op(min, min(x, y))
 Op(minMagSqr, (magSqr(x)<=magSqr(y) ? x : y))
 Op(maxMagSqr, (magSqr(x)>=magSqr(y) ? x : y))
 Op(minMod, minMod(x, y))
-Op(and, x && y)
-Op(or, x || y)
-Op(eqEq, x == y)
-Op(less, x < y)
-Op(lessEq, x <= y)
-Op(greater, x > y)
-Op(greaterEq, x >= y)
 
-weightedOp(multiply, (weight*y))
+BoolOp(and, x && y)
+BoolOp(or, x || y)
+BoolOp(equal, x == y)
+BoolOp(notEqual, x != y)
+BoolOp(less, x < y)
+BoolOp(lessEq, x <= y)
+BoolOp(greater, x > y)
+BoolOp(greaterEq, x >= y)
+
+WeightedOp(multiply, (weight*y))
 
 #undef Op
-#undef weightedOp
+#undef BoolOp
+#undef WeightedOp
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //