data/src/OpenFOAM/fields/expression/expressions.H

/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Copyright (C) 2026 OpenFOAM Foundation
     \\/     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
    Unary and binary functions and operators used by the expression
    templating system

\*---------------------------------------------------------------------------*/

#ifndef expressions_H
#define expressions_H

#include "expressionFunctor.H"
#include "expressionReduce.H"
#include "PstreamReduceOps.H"
#include "expressionEval.H"

#include "UnaryExpression.H"
#include "BinaryExpression.H"

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

namespace Foam
{

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
// Define a unary function or operator given the global function or operator
// name and the operator class that it uses

#define UnaryFunction_(FUNC, Func, Op)                                         \
    FUNC(Func, Op, const X&, const X& x, x)                                    \
    FUNC(Func, Op, const X&, X& x, x)                                          \
    FUNC(Func, Op, X, X&& x, std::move(x))                                     \
    FUNC(Func, Op, const X&, const tmp<X>& x, x)                               \
    FUNC(Func, Op, const X&, tmp<X>& x, x)                                     \
    FUNC(Func, Op, const X&, tmp<X>&& x, x)

#define UnaryFunctionTemplate(Func, Op, XPar, XArg, XVar)                      \
    template                                                                   \
    <                                                                          \
        class X,                                                               \
        class = EnableIfExpressionable<UnaryExpression<X, Op>>                 \
    >                                                                          \
    UnaryExpression<XPar, Op> Func(XArg)                                       \
    {                                                                          \
        return UnaryExpression<XPar, Op>(XVar);                                \
    }                                                                          \

#define UnaryEagerFunctionTemplate(Func, Op, XPar, XArg, XVar)                 \
                                                                               \
    UnaryFunctionTemplate(Func##_, Op, XPar, XArg, XVar)                       \
                                                                               \
    template                                                                   \
    <                                                                          \
        class X,                                                               \
        class = EnableIfExpressionable<UnaryExpression<X, Op>>                 \
    >                                                                          \
    tmp<ResultType<UnaryExpression<XPar, Op>>> Func(XArg)                      \
    {                                                                          \
        return eval(Func##_(Eval<XPar>::eval(XVar)));                          \
    }                                                                          \

#define UnaryOperator(OpSym, Func)                                             \
    UnaryFunction_(UnaryFunctionTemplate, operator OpSym, Func##Op)

#define UnaryFunction(Func)                                                    \
    UnaryFunction_(UnaryFunctionTemplate, Func, Func##Op)

#define UnaryEagerFunction(Func)                                               \
    UnaryFunction_(UnaryEagerFunctionTemplate, Func, Func##Op)

#define UnaryOp(Func)                                                          \
    struct Func##Op                                                            \
    {                                                                          \
        static inline const char* prefix = #Func"(";                           \
        static inline const char postfix = ')';                                \
                                                                               \
        static const signed char precedence =                                  \
            expression::Operation<void>::precedence;                           \
                                                                               \
        template<class Type>                                                   \
        static auto value(const Type& x)                                       \
        {                                                                      \
            return Func(x);                                                    \
        }                                                                      \
    };

#define UnaryOpFunction(Func)                                                  \
    UnaryOp(Func)                                                              \
    UnaryFunction(Func)

#define UnaryOpEagerFunction(Func)                                             \
    UnaryOp(Func)                                                              \
    UnaryEagerFunction(Func)

// Promotion operator (i.e., unary plus). Has no effect. Just facilitates
// expressions with plus signs added for clarity.
UnaryOperator(+, promote)

// Negation operator (i.e., unary minus). Changes the sign of the operand.
UnaryOperator(-, negate)

UnaryFunction(sqr)
UnaryFunction(mag)
UnaryFunction(magSqr)

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
// Define unary reduction functions

#define UnaryReduction_(Func, gFunc, Op)                                       \
                                                                               \
    template<class Expression, class = EnableIfExpressionable<Expression>>     \
    ElementType<Expression> Func                                               \
    (                                                                          \
        const Expression& e,                                                   \
        const bool globalReduce = ReduceType<Expression>::globalReduce,        \
        const label comm = UPstream::worldComm                                 \
    )                                                                          \
    {                                                                          \
        return ReduceType<Expression>::template value<Op>                      \
        (                                                                      \
            e, globalReduce, comm                                              \
        );                                                                     \
    }                                                                          \
                                                                               \
    template<class Expression, class = EnableIfExpressionable<Expression>>     \
    ElementType<Expression> Func(const tmp<Expression>& te)                    \
    {                                                                          \
        auto x = Func(te());                                                   \
        te.clear();                                                            \
        return x;                                                              \
    }                                                                          \
                                                                               \
    template<class Expression, class = EnableIfExpressionable<Expression>>     \
    ElementType<Expression> gFunc                                              \
    (                                                                          \
        const Expression& e,                                                   \
        const label comm = UPstream::worldComm                                 \
    )                                                                          \
    {                                                                          \
        return Func(e, true, comm);                                            \
    }                                                                          \
                                                                               \
    template<class Expression, class = EnableIfExpressionable<Expression>>     \
    ElementType<Expression> gFunc(const tmp<Expression>& te)                   \
    {                                                                          \
        auto x = gFunc(te());                                                  \
        te.clear();                                                            \
        return x;                                                              \
    }

#define UnaryReduction(Func, gFunc)                                            \
    UnaryReduction_(Func, gFunc, Func##Op)

UnaryReduction(sum, gSum);
UnaryReduction(max, gMax);
UnaryReduction(min, gMin);

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
// Define unary average and gAverage functions

template<class Expression, class = EnableIfExpressionable<Expression>>
ElementType<Expression> average
(
    const Expression& e,
    const bool globalReduce = ReduceType<Expression>::globalReduce,
    const label comm = UPstream::worldComm
)
{
    return ReduceType<Expression>::average(e, globalReduce, comm);
}

template<class Expression, class = EnableIfExpressionable<Expression>>
ElementType<Expression> average(const tmp<Expression>& te)
{
    auto x = average(te());
    te.clear();
    return x;
}

template<class Expression, class = EnableIfExpressionable<Expression>>
ElementType<Expression> gAverage
(
    const Expression& e,
    const label comm = UPstream::worldComm
)
{
    return average(e, true, comm);
}

template<class Expression, class = EnableIfExpressionable<Expression>>
ElementType<Expression> gAverage
(
    const tmp<Expression>& te,
    const label comm = UPstream::worldComm
)
{
    auto x = gAverage(te());
    te.clear();
    return x;
}


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
// Weighted average

template
<
    class Expression,
    class WeightExpression,
    class = EnableIfExpressionable<Expression>
>
ElementType<Expression> weightedAverage
(
    const Expression& e,
    const WeightExpression& we,
    const bool globalReduce = ReduceType<Expression>::globalReduce,
    const label comm = UPstream::worldComm
)
{
    return ReduceType<Expression>::weightedAverage
    (
        e,
        we,
        globalReduce,
        comm
    );
}

template
<
    class Expression,
    class WeightExpression,
    class = EnableIfExpressionable<Expression>
>
ElementType<Expression> weightedAverage
(
    const tmp<Expression>& te,
    const WeightExpression& we
)
{
    auto x = weightedAverage(te(), we);
    te.clear();
    return x;
}

template
<
    class Expression,
    class WeightExpression,
    class = EnableIfExpressionable<Expression>
>
ElementType<Expression> gWeightedAverage
(
    const Expression& e,
    const WeightExpression& we,
    const label comm = UPstream::worldComm
)
{
    return weightedAverage(e, we, true, comm);
}

template
<
    class Expression,
    class WeightExpression,
    class = EnableIfExpressionable<Expression>
>
ElementType<Expression> gWeightedAverage
(
    const tmp<Expression>& te,
    const WeightExpression& we,
    const label comm = UPstream::worldComm
)
{
    auto x = gWeightedAverage(te(), we);
    te.clear();
    return x;
}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
// Define a binary function or operator given the global function or operator
// name and the operator class that it uses

#define BinaryFunction__(FUNC, Func, Op, APar, AArg, AVar)                     \
    FUNC(Func, Op, APar, AArg, AVar, const B&, const B& b, b)                  \
    FUNC(Func, Op, APar, AArg, AVar, const B&, B& b, b)                        \
    FUNC(Func, Op, APar, AArg, AVar, B, B&& b, std::move(b))                   \
    FUNC(Func, Op, APar, AArg, AVar, const B&, const tmp<B>& b, b)             \
    FUNC(Func, Op, APar, AArg, AVar, const B&, tmp<B>& b, b)                   \
    FUNC(Func, Op, APar, AArg, AVar, const B&, tmp<B>&& b, b)

#define BinaryFunction_(FUNC, Func, Op)                                        \
    BinaryFunction__(FUNC, Func, Op, const A&, const A& a, a)                  \
    BinaryFunction__(FUNC, Func, Op, const A&, A& a, a)                        \
    BinaryFunction__(FUNC, Func, Op, A, A&& a, std::move(a))                   \
    BinaryFunction__(FUNC, Func, Op, const A&, const tmp<A>& a, a)             \
    BinaryFunction__(FUNC, Func, Op, const A&, tmp<A>& a, a)                   \
    BinaryFunction__(FUNC, Func, Op, const A&, tmp<A>&& a, a)

#define BinaryFunctionTemplate(Func, Op, APar, AArg, AVar, BPar, BArg, BVar)   \
    template                                                                   \
    <                                                                          \
        class A,                                                               \
        class B,                                                               \
        class = EnableIfExpressionable<BinaryExpression<A, B, Op>>             \
    >                                                                          \
    BinaryExpression<APar, BPar, Op> Func(AArg, BArg)                          \
    {                                                                          \
        return BinaryExpression<APar, BPar, Op>(AVar, BVar);                   \
    }                                                                          \

#define BinaryEagerFunctionTemplate(                                           \
    Func, Op, APar, AArg, AVar, BPar, BArg, BVar)                              \
                                                                               \
    BinaryFunctionTemplate(Func##_, Op, APar, AArg, AVar, BPar, BArg, BVar)    \
                                                                               \
    template                                                                   \
    <                                                                          \
        class A,                                                               \
        class B,                                                               \
        class = EnableIfExpressionable<BinaryExpression<A, B, Op>>             \
    >                                                                          \
    tmp<ResultType<BinaryExpression<APar, BPar, Op>>> Func(AArg, BArg)         \
    {                                                                          \
        return eval(Func##_(Eval<APar>::eval(AVar), Eval<BPar>::eval(BVar)));  \
    }                                                                          \

#define BinaryOperator(OpSym, Func)                                            \
    BinaryFunction_(BinaryFunctionTemplate, operator OpSym, Func##Op)

#define BinaryFunction(Func)                                                   \
    BinaryFunction_(BinaryFunctionTemplate, Func, Func##Op)

#define BinaryEagerFunction(Func)                                              \
    BinaryFunction_(BinaryEagerFunctionTemplate, Func, Func##Op)

// Addition operator and sum function
BinaryOperator(+, add);

// Subtraction operator
BinaryOperator(-, subtract);

// Multiplication and/or outer-product operator
BinaryOperator(*, multiply);

// Division operator
BinaryOperator(/, divide);

// Inner product (dot) operator
BinaryOperator(&, inner);

// Cross product operator
BinaryOperator(^, cross);

// Maximum functions
BinaryFunction(max);

// Minimum function
BinaryFunction(min);

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

} // End namespace Foam

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#endif

// ************************************************************************* //