reserve A for preIfWhileAlgebra;
reserve A for Euclidean preIfWhileAlgebra;
reserve X for non empty countable set;
reserve T for Subset of Funcs(X, INT);
reserve f for Euclidean ExecutionFunction of A, Funcs(X, INT), T;

theorem Th22:
  for x being Variable of f for s being Element of Funcs(X, INT)
  holds (.x).s = s.x
proof
  let x be Variable of f;
  let s be Element of Funcs(X, INT);
  thus (.x).s = s.((x^(A,f)).s) by Def19
    .= s.x;
end;
