church-rosser theorem

Church-Rosser Theorem

   <theory> A property of a {reduction} system that states that
   if an expression can be reduced by zero or more reduction
   steps to either expression M or expression N then there exists
   some other expression to which both M and N can be reduced.
   This implies that there is a unique {normal form} for any
   expression since M and N cannot be different normal forms
   because the theorem says they can be reduced to some other
   expression and normal forms are irreducible by definition.  It
   does not imply that a normal form is reachable, only that if
   reduction terminates it will reach a unique normal form.

   (1995-01-25)