Definitions | s = t, t T, x:AB(x), x:A. B(x), E, {x:A| B(x)} , a:A fp B(a), E(X), b, strong-subtype(A;B), P Q, ES, Type, AbsInterface(A), type List, e X, f(a), , x.A(x), es-le-before(es;e), , X(e), mapfilter(f;P;L), concat(ll), es-interface-history(es;X;e), x:A B(x), left + right, let x,y = A in B(x;y), t.1, case b of inl(x) => s(x) | inr(y) => t(y), if b then t else f fi |