C+
C NAME:
C	step_fnc
C PROCEDURE:
C	Never tested
C-
	iStepFnc(X) = 1-nint(1-sign(1.,X))/2	! 1 for X>=0, 0 for X<0
	iStepPM1(X) = iStepFnc(X)-iStepFnc(-X)	! -1 for X<0, 1 for X>=0
	iBlockFnc(X1,X2) = (iStepFnc(X1)+iStepFnc(-X2))/2