algebrite/sources/condense.coffee

Computer Algebra System in Coffeescript

# Condense an expression by factoring common terms.
                                                                                


Eval_condense = ->
	push(cadr(p1))
	Eval()
	Condense()

Condense = ->
	prev_expanding = expanding
	expanding = 0
	save()
	yycondense()
	restore()
	expanding = prev_expanding

yycondense = ->
	#expanding = 0

	p1 = pop()

	if (car(p1) != symbol(ADD))
		push(p1)
		return

	# get gcd of all terms

	p3 = cdr(p1)
	push(car(p3))
	p3 = cdr(p3)
	while (iscons(p3))
		push(car(p3))
		gcd()
		p3 = cdr(p3)

	#printf("condense: this is the gcd of all the terms:\n")
	#print(stdout, stack[tos - 1])

	# divide each term by gcd

	inverse()
	p2 = pop()
	push(zero)
	p3 = cdr(p1)
	while (iscons(p3))
		push(p2)
		push(car(p3))
		multiply()
		add()
		p3 = cdr(p3)

	# We multiplied above w/o expanding so sum factors cancelled.

	# Now we expand which which normalizes the result and, in some cases,
	# simplifies it too (see test case H).

	yyexpand()

	# multiply result by gcd

	push(p2)
	divide()