GLR Machine

parseSS calls machine/8 using:

machine([0],ZLSS,[],[],accept,[],SS,_)

Index	Parameter	Input/Output	Value	Description
1	Control Stack	Input	[0]	List encodes stack. Begin at state 0.
2	Input	Input	Output of parsePF	List of (zero-level) constituents.
3	Structure Stack	Input	[]	List encodes stack. Each element is a constituent.
4	Environment Stack	Input	[]	List encodes stack. Used for local storage during LR parsing.
5	Control Stack	Output	accept	Not a stack anymore. Just the end state.
6	Input	Output	[]	Input consumed.
7	Structure Stack	Output	Parse	Not a stack anymore. Just a single constituent.
8	Environment Stack	Output	_	Don't care.

Definition of machine/8:

machine(accept,    []    ,[SS],_, accept,[],SS, _  ) :- !.
machine([State|CS],[I|Is],SS,  ES,CS2,   I2,SS2,ES2) :-
	ss0Cat(I,C),
	glrMachineHook,				  % platform-specific
	action(State,C,[State|CS],[I|Is],SS,ES,CS1,I1,SS1,ES1,_, _Action),
	machine(CS1,I1,SS1,ES1,CS2,I2,SS2,ES2).

% need to deal with the endmarker $ as a special category
ss0Cat(I,C) :- cat(I,C), !.
ss0Cat('$','$').

References: Constituent Structure