algebrite/sources/degree.coffee

Computer Algebra System in Coffeescript

### deg =====================================================================

Tags
----
scripting, JS, internal, treenode, general concept

Parameters
----------
p,x

General description
-------------------
Returns the degree of polynomial p(x).

###


Eval_degree = ->
  push(cadr(p1))
  Eval()
  push(caddr(p1))
  Eval()
  p1 = pop()
  if (p1 == symbol(NIL))
    guess()
  else
    push(p1)
  degree()

#-----------------------------------------------------------------------------
#
#  Find the degree of a polynomial
#
#  Input:    tos-2    p(x)
#
#      tos-1    x
#
#  Output:    Result on stack
#
#  Note: Finds the largest numerical power of x. Does not check for
#  weirdness in p(x).
#
#-----------------------------------------------------------------------------

#define POLY p1
#define X p2
#define DEGREE p3

degree = ->
  save()
  p2 = pop()
  p1 = pop()
  p3 = zero
  yydegree(p1)
  push(p3)
  restore()

yydegree = (p) ->
  if (equal(p, p2))
    if (isZeroAtomOrTensor(p3))
      p3 = one
  else if (car(p) == symbol(POWER))
    if (equal(cadr(p), p2) && isNumericAtom(caddr(p)) && lessp(p3, caddr(p)))
      p3 = caddr(p)
  else if (iscons(p))
    p = cdr(p)
    while (iscons(p))
      yydegree(car(p))
      p = cdr(p)