!***************************************************
!* Chebyshev Approximation of a user defined real  *
!* function FUNC(X) in double precision.           *
!* ----------------------------------------------- *
!* SAMPLE RUN:                                     *
!* (Approximate sin(x) from x=0 to x=PI).          *
!*                                                 *
!* Chebyshev coefficients (N=10):                  *
!*  0.944002431536470                              *
!* -2.844946500601964E-017                         *
!* -0.499403258270407                              *
!* -8.951173136040325E-017                         *
!*  2.799207961754557E-002                         *
!* -1.252470349655255E-016                         *
!* -5.966951958007059E-004                         *
!*  2.622901895676933E-016                         *
!*  6.704175523811369E-006                         *
!*  2.576064361825559E-017                         *
!*      X           Chebyshev Eval.     SIN(X)     *
!*  -----------------------------------------------*
!*  0.00000000E+00  0.46095096E-07  0.00000000E+00 *
!*  0.34906585E+00  0.34202018E+00  0.34202014E+00 *
!*  0.69813170E+00  0.64278758E+00  0.64278761E+00 *
!*  0.10471976E+01  0.86602545E+00  0.86602540E+00 *
!*  0.13962634E+01  0.98480773E+00  0.98480775E+00 *
!*  0.17453293E+01  0.98480773E+00  0.98480775E+00 *
!*  0.20943951E+01  0.86602545E+00  0.86602540E+00 *
!*  0.24434610E+01  0.64278758E+00  0.64278761E+00 *
!*  0.27925268E+01  0.34202018E+00  0.34202014E+00 *
!*  0.31415927E+01  0.46095096E-07  0.12246064E-15 *
!*                                                 *
!*               F90 Release By J-P Moreau, Paris. *
!*                      (www.jpmoreau.fr)          *
!***************************************************
! To link with Chebyshev.f90.

PROGRAM TESTCHEBY

parameter(NMAX=50,ZERO=0.d0)

real*8 PI,X0,X1, COEFF(NMAX)
real*8 DX, X

PI=4.d0*datan(1.d0)

N=10
X0=ZERO; X1=PI

call CHEBFT(X0,X1,COEFF,N)

write(*,10)  N
do I=1, N
 print *, COEFF(I)
end do

DX=(X1-X0)/(N-1)
X=X0-DX

print *,'       X         Chebyshev Eval.     SIN(X)    '
print *,' ----------------------------------------------' 
do I=1, N
  X=X+DX
  write(*,20) X, CHEBEV(X0,X1,COEFF,N,X), DSIN(X)
end do

10 format(' Chebyshev coefficients (N=',I2,'):') 
20 format(3E16.8)

END

!user defined function
real*8 function FUNC(x)
real*8 x
FUNC=DSIN(x)
return
end

!end of file Tchebysh.f90