English
SubtypeVal composed with toSubtype equals the constant val function.
Русский
SubtypeVal, сопоставляемое toSubtype, даёт константу Subtype.val.
LaTeX
$$\operatorname{subtypeVal}(p) \circ \operatorname{toSubtype}(p) = \lambda _ . \operatorname{Subtype.val}$$
Lean4
@[simp]
theorem subtypeVal_toSubtype {α : TypeVec n} (p : α ⟹ «repeat» n Prop) :
subtypeVal p ⊚ toSubtype p = fun _ => Subtype.val :=
by
ext i x
induction i <;> simp only [toSubtype, comp, subtypeVal] at *
simp [*]