!
! File: ~/numerical/nfact.f90
!
! Quick and dirty test program to test recursive f90 function
! to evaluate n!
!
! E.C.G. (12-98)
!
PROGRAM test_nfact

  IMPLICIT NONE
  INTEGER :: n

  DO
     PRINT *, 'n = ?'
     READ  *,  n
     PRINT *, 'n! = ', fact(n)
  END DO

CONTAINS

  RECURSIVE FUNCTION fact( n ) RESULT( nfact )

    IMPLICIT NONE
    INTEGER, INTENT(IN) :: n
    INTEGER :: nfact

    IF ( n < 0 ) THEN
       nfact = 0
    ELSE IF ( ( n == 0 ) .OR. ( n == 1 ) ) THEN
       nfact = 1
    ELSE
       nfact = n * fact( n - 1 )
    END IF

  END FUNCTION fact

END PROGRAM test_nfact