FUNCTION distance_point_to_line,A,B,C,P=u
;+
;d=distance_point_to_line(A,B,C) finds the
;Euclidean distance from a line described by two
;points A and B to a point C. All of the points
;are n-dimensional vectors, where n>1. If A=B then
;the distance between two points A and C is measured.
;
;KEYWORD
;D=distance_point_to_line(A,B,C,P=u)
;returns the point P on the line closest to the point C.
;
;H. Rhody
;July, 2004
;-

IF Min([n_elements(A),n_elements(B),n_elements(C)]) LT 2 THEN $
	MESSAGE,'Vectors must be at least 2D'

IF MAX(A NE B) EQ 0 THEN BEGIN $ ;A=B case
	u=A
	return,sqrt(inprod(A-C,A-C))
ENDIF

v=C-A
w=B-A
t=inprod(v,w)/inprod(w,w)
u=A+t*w
return,sqrt(inprod(u-C,u-C))

END