#-----------------------------------------------------------------------------
#
#  Author : philippe.billet@noos.fr
#
#  Dirac function dirac(x)
#  dirac(-x)=dirac(x)
#  dirac(b-a)=dirac(a-b)
#-----------------------------------------------------------------------------



Eval_dirac = ->
  push(cadr(p1))
  Eval()
  dirac()

dirac = ->
  save()
  ydirac()
  restore()

#define p1 p1

ydirac = ->

  p1 = pop()


  
  if (isdouble(p1))
    if (p1.d == 0) 
      push_integer(1)
      return
    else 
      push_integer(0)
      return

  if (isrational(p1))
    if (MZERO(mmul(p1.q.a,p1.q.b))) 
      push_integer(1)
      return
    else 
      push_integer(0)
      return
    
  
  if (car(p1) == symbol(POWER))
    push_symbol(DIRAC)
    push(cadr(p1))
    list(2)
    return
  
  if (isnegativeterm(p1))
    push_symbol(DIRAC)
    push(p1)
    negate()
    list(2)
    return
  
  if (isnegativeterm(p1) || (car(p1) == symbol(ADD) && isnegativeterm(cadr(p1))))
    push(p1)
    negate()
    p1 = pop()
  
     
  push_symbol(DIRAC)
  push(p1)
  list(2)