C+
C NAME:
C	Chebyshev
C PURPOSE:
C	Evaluate value of Chebyshev polynomial in given point X
C CATEGORY:
C	Math: orthogonal polynomials
C CALLING SEQUENCE:
	function Chebyshev(X,N)
C INPUTS:
C	X		real		the Chebyshev polynomial is evaluated in X
C	N		integer		degree of Chebyshev polynomial
C OUTPUTS:
C	Chebyshev	real		value of n-th degree Chebyshev polynomial in XS
C RESTRICTIONS:
C	The degree N must be larger/equal zero
C PROCEDURE:
C	Evaluation is based three-term recurrence relation for Chebyshev 
C	polynomials (T_0 = 1 ; T_1 = x)
C	T_i = 2xT_i-1 - T_i-2 ; i = 2,3,4, ...
C MODIFICATION HISTORY:
C	DEC-1991; Paul Hick (UCSD)
C-
	    real	X
	    integer	N

	Chebyshev = 1		! N = 0
	if (N .eq. 0) return

	Chebyshev = X		! N = 1
	if (N .eq. 1) return

	X2 = 2*X
	CM1 = 1
	do I=2,N
	    CM2 = CM1			! degree I-2
	    CM1 = Chebyshev		! degree I-1
	    Chebyshev = X2*CM1-CM2	! degree I (by recursion)
	end do

	return
	end