Class new title: ParseStack
	subclassof: Object
	fields: 'position length'
	declare: ''

init 
	[position _ 0.
	length _ position]

length [length]

pop: t1 
	[position _ position - t1.
	position < 0  [user notify: 'Parse stack underflow']]

position [position]

push: t1 
	[position _ position + t1.
	position > length  [length _ position]]