#ifndef MGU
#define MGU

#include "term.h"
#include "termlist.h"
#include "substitution.h"

//! A special constant do denote failure.
/**
 * \c NULL already denotes equality, so an extra signal is needed to
 * denote that a unification fails.
 * \todo Find a portable solution for this \c MGUFAIL constant:
 * maybe a pointer to some special constant.
 */
#define MGUFAIL (Termlist) -1

Termlist termMguTerm (Term t1, Term t2);
void termMguInTerm (Term t1, Term t2, void (*iterator) ());
void termMguSubTerm (Term t1, Term t2, void (*iterator) (),
		     const Termlist inverses, Termlist keylist);

#endif