FUNCTION g_rand, dum
; Subroutine to return a normally distributed deviate with zero mean
; and unit variance (a la Abramowitz/Stegun p953, Acceptance-rejection(4).)
;
; 6/7/91 dd
;

COMMON rand, seed

; Comment this out to use systime for seed
; if n_elements(seed) eq 0 then seed = 17

REPEAT BEGIN
  u1 = randomu(seed)
  u2 = randomu(seed)
  x = -1.0*ALOG(u1)
ENDREP UNTIL ( (x-1.0)*(x-1.0) LT -2.0*ALOG(u2) )

IF randomu(seed) LT 0.5 THEN x = -1.0*x

RETURN, x

END