program array practice
c
c       John Mahaffy,  Penn State University, CmpSc 201 Example
c       1/26/96
c
*  We will try to utilize MAX, MIN, Implied Do-Loops, Data statements,
*  and FORTRAN 90 constructs fortest preparation
      IMPLICIT NONE
      INTEGER I,J,K
      REAL, DIMENSION(10) :: A,B,C=(/(I,I=1,10)/),GSUM,GM,GX
c   Associating a dimension with gmult treats it as an array containing
c   numbers, not a function that must be evaluated.
      INTERFACE GMULT
      FUNCTION GMULT (A,B)
      REAL A(:),B(:)
      REAL GMULT(SIZE(A))
      END FUNCTION GMULT
      END INTERFACE
      EXTERNAL GMULT
      DATA A/3*2.5,4*2.,7.,9.,11./
      DATA B/4*3.,2*5.,2.,9.,1.4,3./
      OPEN (12,FILE='ARRAY.DATA')
      DO 100 J=1,10
         WRITE (12,20) A(J),B(J),C(J)
 20      FORMAT ('A= ',f5.2,'  B= ',f5.2,'  C= ',f5.2)
 100  CONTINUE
      CALL XSUM (A,B,GSUM)
      GX=GMULT(A,B)
      DO 110 K=1,10
         WRITE (12,200) A(K),B(K),GSUM(K),GX(K)
 200     FORMAT ('A= ',f5.2,'  B=',f5.2,'  GSUM=',f5.2,'  GX=',f5.2)
 110  CONTINUE
      STOP
      END
      SUBROUTINE XSUM (E,F,GSUM)
      IMPLICIT NONE
      REAL, DIMENSION (10) :: E,F,GSUM,G
      G(1:10) = E(1:10) + F(1:10)
c   SUM returns a single number.  No need to load it into an array.
c   the array just gets the same number in all elements.
      GSUM=SUM(G(1:10))
      RETURN
      END
      FUNCTION GMULT(E,F)
      IMPLICIT NONE
      INTEGER I
      REAL E(:),F(:)
      REAL GMULT(SIZE(E))
      DO 120 I=1,10
         GMULT(I)=E(I)*F(I)
  120 CONTINUE    
      END