function WMIRFILT, x
;+
; NAME:
; 	 WMIRFILT 
;
; PURPOSE:
;	This function applies a (-1)^t modulation.
;
; CATEGORY:
;	Wavelets
;
; CALLING SEQUENCE:
;    h = WMIRFILT(x)
;
; INPUTS:
;    x:   1-d signal
;
; OUTPUTS:
;    h: a 1-d signal with DC frequency content shifted
;        to Nyquist frequency
;
; EXAMPLE:
;
; SEE ALSO:
;    wdndydhi
;
; PROCEDURE:
;	h(t) = (-1)^(t-1) * x(t),  1 <= t <= length(x)
;
; MODIFICATION HISTORY:
; 	Written by:	Amara Graps		October, 1994
;Translated from MatLab Wavelab routine: mirrorfilt.m
;-

;use the IDL way to create an index array
a = 1 & b = 1 & c = N_ELEMENTS(x)
indx_arr = WMKIARRY( a, b, c) + 1		;wmkiarry has -1 in indices
	
y = -( (-1)^(indx_arr) ) * x

;	
; Algorithm Source:  WaveLab Version 0.600
; WaveLab WWW site: http://playfair.stanford.edu/ 
; WaveLab Questions? e-mail wavelab@playfair.stanford.edu
;   
    

RETURN, y 
END 
;***************************************************