text: //===-- lib/evaluate/fold-complex.cpp -------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  #include "fold-implementation.h"
  
  namespace Fortran::evaluate {
  
  template<int KIND>
  Expr<Type<TypeCategory::Complex, KIND>> FoldIntrinsicFunction(
      FoldingContext &context,
      FunctionRef<Type<TypeCategory::Complex, KIND>> &&funcRef) {
    using T = Type<TypeCategory::Complex, KIND>;
    ActualArguments &args{funcRef.arguments()};
    auto *intrinsic{std::get_if<SpecificIntrinsic>(&funcRef.proc().u)};
    CHECK(intrinsic);
    std::string name{intrinsic->name};
    if (name == "acos" || name == "acosh" || name == "asin" || name == "asinh" ||
        name == "atan" || name == "atanh" || name == "cos" || name == "cosh" ||
        name == "exp" || name == "log" || name == "sin" || name == "sinh" ||
        name == "sqrt" || name == "tan" || name == "tanh") {
      if (auto callable{context.hostIntrinsicsLibrary()
                            .GetHostProcedureWrapper<Scalar, T, T>(name)}) {
        return FoldElementalIntrinsic<T, T>(
            context, std::move(funcRef), *callable);
      } else {
        context.messages().Say(
            "%s(complex(kind=%d)) cannot be folded on host"_en_US, name, KIND);
      }
    } else if (name == "conjg") {
      return FoldElementalIntrinsic<T, T>(
          context, std::move(funcRef), &Scalar<T>::CONJG);
    } else if (name == "cmplx") {
      using Part = typename T::Part;
      if (args.size() == 1) {
        if (auto *x{UnwrapExpr<Expr<SomeComplex>>(args[0])}) {
          return Fold(context, ConvertToType<T>(std::move(*x)));
        }
        Expr<SomeType> re{std::move(*args[0].value().UnwrapExpr())};
        Expr<SomeType> im{AsGenericExpr(Constant<Part>{Scalar<Part>{}})};
        return Fold(context,
            Expr<T>{ComplexConstructor<KIND>{ToReal<KIND>(context, std::move(re)),
                ToReal<KIND>(context, std::move(im))}});
      }
      CHECK(args.size() == 2 || args.size() == 3);
      Expr<SomeType> re{std::move(*args[0].value().UnwrapExpr())};
      Expr<SomeType> im{args[1] ? std::move(*args[1].value().UnwrapExpr())
                                : AsGenericExpr(Constant<Part>{Scalar<Part>{}})};
      return Fold(context,
          Expr<T>{ComplexConstructor<KIND>{ToReal<KIND>(context, std::move(re)),
              ToReal<KIND>(context, std::move(im))}});
    } else if (name == "merge") {
      return FoldMerge<T>(context, std::move(funcRef));
    }
    // TODO: cshift, dot_product, eoshift, matmul, pack, product,
    // reduce, spread, sum, transfer, transpose, unpack
    return Expr<T>{std::move(funcRef)};
  }
  
  template<int KIND>
  Expr<Type<TypeCategory::Complex, KIND>> FoldOperation(
      FoldingContext &context, ComplexConstructor<KIND> &&x) {
    if (auto array{ApplyElementwise(context, x)}) {
      return *array;
    }
    using Result = Type<TypeCategory::Complex, KIND>;
    if (auto folded{OperandsAreConstants(x)}) {
      return Expr<Result>{
          Constant<Result>{Scalar<Result>{folded->first, folded->second}}};
    }
    return Expr<Result>{std::move(x)};
  }
  
  FOR_EACH_COMPLEX_KIND(template class ExpressionBase, )
  template class ExpressionBase<SomeComplex>;
  }
  