Question

我是vector-vector-scalar multiplication。标量可以是整数类型或类型实数。我还必须允许向量与标量（v = u * scal）和反向（v = scal * u）相乘。以下代码给出了错误，因为它无法区分这两者。一种解决方案是具有四个函数来处理整数和实数标量类型，并且每个函数都具有post和pre-multiply操作。有没有办法避免有四个功能，只有两个？

这是指定运算符（*）

!> Multiplies a vector by a scalar such that one can write
!> v = scal * u and v = u * scal.
Procedure :: vector_scalar_postmultiply
Procedure, Pass (ub) :: vector_scalar_premultiply
Generic :: Operator (*) => vector_scalar_postmultiply, &
                           vector_scalar_premultiply

这是后乘法函数

!> Multiplies a vector by a scalar such that one can write
!> v = scal * u and v = u * scal.
Procedure :: vector_scalar_postmultiply
Procedure, Pass (ub) :: vector_scalar_premultiply
Generic :: Operator (*) => vector_scalar_postmultiply, &
                     vector_scalar_premultiply

Function vector_scalar_postmultiply  &
(                                    &
  u,                                 & 
  scal                               &
)                                    &
  Result (v)

  !!$ In.
  Class (Vector), Intent(in) :: u
  Class (*), Intent(in) :: scal

  !!$ Out.
  Type (Vector) :: v

  Select Type (scal)

  !!$ scal points to integer intrinsic type. 
  Type Is (Integer)
    v% x = Real (scal) *  u% x
    v% y = Real (scal) *  u% y
    v% z = Real (scal) *  u% z

  !!$ scal points to real intrinsic type. 
  Type Is (Real)
    v% x = scal *  u% x
    v% y = scal *  u% y
    v% z = scal *  u% z

  End Select

End Function vector_scalar_postmultiply

这是预乘函数

Function vector_scalar_premultiply  &
(                                   &
  scalb,                            & 
  ub                                &
)                                   &
  Result (vb)

  !!$ In.
  Class (*), Intent(in) :: scalb
  Class (Vector), Intent(in) :: ub

  !!$ Out.
  Type (Vector) :: vb

  Select Type (scalb)

  !!$ scal points to integer intrinsic type. 
  Type Is (Integer)
    vb% x = Real (scalb) *  ub% x
    vb% y = Real (scalb) *  ub% y
    vb% z = Real (scalb) *  ub% z

  !!$ scal points to real intrinsic type. 
  Type Is (Real)
    vb% x = scalb *  ub% x
    vb% y = scalb *  ub% y
    vb% z = scalb *  ub% z  

  End Select

End Function vector_scalar_premultiply

错误如下

gfortran -o build/lib/foul.o -c -ffree-form -g -J./build/lib lib/foul.f
gfortran -o build/lib/vectors.o -c -ffree-form -g -J./build/lib lib/vectors.f
lib/vectors.f:214.28:

Generic :: Operator (*) => vector_scalar_postmultiply, &
                    1
Error: 'vector_scalar_postmultiply' and 'vector_scalar_premultiply' for GENERIC '*' 
at (1) are ambiguous

scons: *** [build/lib/vectors.o] Error 1
scons: building terminated because of errors.

Fortran OOP发布并预加倍

0 个答案: