#check list.map

variable l : list nat

#check l.1 -- Error l is not a structure

#check (1, 2).5 -- Error insufficient fields

example (l : list nat) : list nat :=
l.forr (λ x, x + 1) -- Error there is no list.forr

example (A : Type) (a : A) : A :=
a.symm -- Error type of 'a' is not a constant application

example (A : Type) (a : A) : A :=
eq.sym -- Error unknown identifier

example (l : list nat) : list nat :=
l.for (λ x, x + 1)

example (l : list nat) : list nat :=
l.for (λ x, x + 1)

example (a b : nat) (h : a = b) : b = a :=
h.symm

example (a b : nat) (h : a = b) : b = a :=
h.symm