;+
;
; @file_comments
; computes the determinant of n 2 by 2 arrays Z2DS is an 2*2*n array
;
; @categories
; Without loop
;
; @param A {in}{required}
; n element array
; Defined as z2ds[0, 0, *] = z1d00
;
; @param B {in}{required}
; n element array
; Defined as z2ds[0, 1, *] = z1d01
;
; @param C {in}{required}
; n element array
; Defined as z2ds[1, 0, *] = z1d10
;
; @param D {in}{required}
; n element array
; Defined as z2ds[1, 1, *] = z1d11
;
; @returns
; n elements array, the determinent of each 2*2 arrrays
;
; @examples
; IDL> a=findgen(2,2,5)
; IDL> print, determ2(a)
; IDL> FOR i=0,4 DO print, determ(a[*,*,i])
;
; @history
; S. Masson (smasson\@lodyc.jussieu.fr)
; July 11th, 2002
;
; @version
; $Id$
;
;-
FUNCTION determ2, a, b, c, d
;
  compile_opt idl2, strictarrsubs
;
  CASE n_params() OF
    1:res = a[0, 0, *]*a[1, 1, *]-a[0, 1, *]*a[1, 0, *]
    4:res = a[*]*d[*]-c[*]*b[*]
    ELSE:stop
  ENDCASE

  RETURN, res
END