Il Linguaggio Fortran 90/95

276 Unità di Programma
!
INTEGER, PARAMETER :: max_test = 8
REAL,DIMENSION(max_test) :: x_test=(/-10.,-5.,-1.,0.,1.,5.,10.,15./)
REAL,DIMENSION(max_test) :: series_exp, intrinsic_exp, rel_err
INTEGER :: i
INTERFACE
REAL ELEMENTAL FUNCTION user_exp(x) RESULT(exp_x)
IMPLICIT NONE
REAL, INTENT(IN) :: x
END FUNCTION user_exp
END INTERFACE
series_exp = user_exp(x_test)
intrinsic_exp = EXP(x_test)
rel_err = ABS((series_exp - intrinsic_exp)/intrinsic_exp)
WRITE(*,’(T9,A,T17,A,T30,A,T43,A,/,T6,52("="))’) &
"x", "serie", "intrinseca", "errore relativo"
DO i =1,max_test
WRITE(*,’(F10.1,3ES15.6)’) x_test(i), series_exp(i), &
intrinsic_exp(i), rel_err(i)
END DO
END PROGRAM prova_user_exp
!
!++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
!
REAL ELEMENTAL FUNCTION user_exp(x) RESULT(exp_x)
!
!Scopo: Stimare il valore di EXP(x) usando i primi 30 termini
! dello sviluppo in serie di the Taylor.
!
IMPLICIT NONE
REAL, INTENT(IN) :: x
INTEGER, PARAMETER :: n_terms = 20
INTEGER :: n
REAL :: factor
!
exp_x = 1
factor = 1
DO n =1,n_terms -1
factor = factor*x/n
exp_x = exp_x + factor
END DO
END FUNCTION user_exp