chebft.f90

来自「本电子版分01.02.03与《Visual Fortran常用数值算法集》配套使」· F90 代码 · 共 24 行

SUBROUTINE chebft(a,b,c,n,func)
INTEGER n,NMAX
REAL a,b,c(n),func,PI
EXTERNAL func
PARAMETER (NMAX=50, PI=3.141592653589793d0)
INTEGER j,k
REAL bma,bpa,fac,y,f(NMAX)
DOUBLE PRECISION sum
bma=0.5*(b-a)
bpa=0.5*(b+a)
do k=1,n
  y=cos(PI*(k-0.5)/n)
  f(k)=func(y*bma+bpa)
end do
fac=2./n
do j=1,n
  sum=0.d0
  do k=1,n
    sum=sum+f(k)*cos((PI*(j-1))*((k-0.5d0)/n))
  end do
  c(j)=fac*sum
end do
END SUBROUTINE chebft