what I'm interested in, is (cat verintlin.f):
SUBROUTINE VERINT (
I KLON , KLAT , KLEV , KINT , KHALO
I , KLON1 , KLON2 , KLAT1 , KLAT2
I , KP , KQ , KR
R , PARG , PRES
R , PALFH , PBETH
R , PALFA , PBETA , PGAMA )
C
C*******************************************************************
C
C VERINT - THREE DIMENSIONAL INTERPOLATION
C
C PURPOSE:
C
C THREE DIMENSIONAL INTERPOLATION
C
C INPUT PARAMETERS:
C
C KLON NUMBER OF GRIDPOINTS IN X-DIRECTION
C KLAT NUMBER OF GRIDPOINTS IN Y-DIRECTION
C KLEV NUMBER OF VERTICAL LEVELS
C KINT TYPE OF INTERPOLATION
C = 1 - LINEAR
C = 2 - QUADRATIC
C = 3 - CUBIC
C = 4 - MIXED CUBIC/LINEAR
C KLON1 FIRST GRIDPOINT IN X-DIRECTION
C KLON2 LAST GRIDPOINT IN X-DIRECTION
C KLAT1 FIRST GRIDPOINT IN Y-DIRECTION
C KLAT2 LAST GRIDPOINT IN Y-DIRECTION
C KP ARRAY OF INDEXES FOR HORIZONTAL DISPLACEMENTS
C KQ ARRAY OF INDEXES FOR HORIZONTAL DISPLACEMENTS
C KR ARRAY OF INDEXES FOR VERTICAL DISPLACEMENTS
C PARG ARRAY OF ARGUMENTS
C PALFH ALFA HAT
C PBETH BETA HAT
C PALFA ARRAY OF WEIGHTS IN X-DIRECTION
C PBETA ARRAY OF WEIGHTS IN Y-DIRECTION
C PGAMA ARRAY OF WEIGHTS IN VERTICAL DIRECTION
C
C OUTPUT PARAMETERS:
C
C PRES INTERPOLATED FIELD
C
C HISTORY:
C
C J.E. HAUGEN 1 1992
C
C*******************************************************************
C
IMPLICIT NONE
C
INTEGER KLON , KLAT , KLEV , KINT , KHALO,
I KLON1 , KLON2 , KLAT1 , KLAT2
C
INTEGER KP(KLON,KLAT), KQ(KLON,KLAT), KR(KLON,KLAT)
REAL PARG(2-KHALO:KLON+KHALO-1,2-KHALO:KLAT+KHALO-1,KLEV) ,
R PRES(KLON,KLAT) ,
R PALFH(KLON,KLAT) , PBETH(KLON,KLAT) ,
R PALFA(KLON,KLAT,4) , PBETA(KLON,KLAT,4),
R PGAMA(KLON,KLAT,4)
C
INTEGER JX, JY, IDX, IDY, ILEV
REAL Z1MAH, Z1MBH
C
C LINEAR INTERPOLATION
C
DO JY = KLAT1,KLAT2
DO JX = KLON1,KLON2
IDX = KP(JX,JY)
IDY = KQ(JX,JY)
ILEV = KR(JX,JY)
C
PRES(JX,JY) = PGAMA(JX,JY,1)*(
C
+ PBETA(JX,JY,1)*( PALFA(JX,JY,1)*PARG(IDX-1,IDY-1,ILEV-1)
+ + PALFA(JX,JY,2)*PARG(IDX ,IDY-1,ILEV-1) )
+ + PBETA(JX,JY,2)*( PALFA(JX,JY,1)*PARG(IDX-1,IDY ,ILEV-1)
+ + PALFA(JX,JY,2)*PARG(IDX ,IDY ,ILEV-1) ) )
C +
+ + PGAMA(JX,JY,2)*(
C +
+ PBETA(JX,JY,1)*( PALFA(JX,JY,1)*PARG(IDX-1,IDY-1,ILEV )
+ + PALFA(JX,JY,2)*PARG(IDX ,IDY-1,ILEV ) )
+ + PBETA(JX,JY,2)*( PALFA(JX,JY,1)*PARG(IDX-1,IDY ,ILEV )
+ + PALFA(JX,JY,2)*PARG(IDX ,IDY ,ILEV ) ) )
ENDDO
ENDDO
C
RETURN
END
i.e., real Fortran code, not just intrinsics :-)