;+
; NAME:
;	LEGPOLY
;
; PURPOSE:
;	Evaluate a sum of legendre polynomial functions of a variable.
;
; CATEGORY:
;	C1 - Operations on polynomials.
;
; CALLING SEQUENCE:
;	Result = LEGPOLY(X,C)
;
; INPUTS:
;	X:	The variable.  This value can be a scalar, vector or array.
;
;	C:	The vector of legendre polynomial coefficients.  The degree of
;		of the polynomial is N_ELEMENTS(C) - 1.
;
; OUTPUTS:
;	LEGPOLY returns a result equal to:
;		 C[0] + c[1] * LEGENDRE(X,1) + c[2]*LEGENDRE(x,2) + ...
;
; COMMON BLOCKS:
;	None.
;
; SIDE EFFECTS:
;	None.
;
; RESTRICTIONS:
;	Designed for X between -1 and 1.
;
; PROCEDURE:
;	Straightforward.
;
; MODIFICATION HISTORY:
;       LAY, Written, Dec 2010
;
;	BASED ON RSI FUNCTION POLY
; $Id: //depot/idl/IDL_70/idldir/lib/poly.pro#2 $
;
; Copyright (c) 1983-2008, ITT Visual Information Solutions. All
;       rights reserved. Unauthorized reproduction is prohibited.
;	DMS, Written, January, 1983.
;   CT, RSI, Nov 2004: Special case for zero-order polynomial.
;       Be sure to still return an array.
;-

FUNCTION LEGPOLY,X,C

    compile_opt idl2

    on_error,2		;Return to caller if an error occurs

    N = N_ELEMENTS(C)-1	;Find degree of polynomial

    ; Special case for N=0. Be sure to return a result of the
    ; same type and array dimensions as X.
    if (n eq 0) then $
        return, x*0 + c[0]

    leg_last = x*0 + 1.
    leg = x
    Y = c[0] + c[1] * x
    for l=2,n do begin
       y += legendre(x,l)
    end

    return,y

end