Section Length_4.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
Notation "l1 =l= l2" := (EqL l1 l2) (at level 80, right associativity).
Global Instance eqL_equivalence : Equivalence EqL.

Lemma ex_lg : forall A B, exists l, Q_Cong l /\ l A B.