Pure Subroutine Example

    PURE SUBROUTINE G(x,y,z) 
     IMPLICIT NONE
     REAL, INTENT(OUT), DIMENSION(:) :: z
     REAL, INTENT(IN),  DIMENSION(:) ::  x, y
     INTEGER i
     INTERFACE
      REAL FUNCTION F(x,y)
       REAL, INTENT(IN) ::  x, y
      END FUNCTION F
     END INTERFACE
!      ...
      FORALL(i=1:SIZE(z)) z(i) = F(x(i),y(i))
    END SUBROUTINE G

Note:

• invokes pure procedure,
• interface not mandatory but is a very good idea.

Example of use,

    CALL G(x,y,res)

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