English
If HasSubst a holds, then multiplying on the left by any substitution b preserves HasSubst: HasSubst a → HasSubst b → HasSubst (b * a).
Русский
Если HasSubst a выполняется, умножение слева на любую подстановку b сохраняет HasSubst: HasSubst a → HasSubst b → HasSubst (b * a).
LaTeX
$$HasSubst a → HasSubst b → HasSubst (b * a)$$
Lean4
theorem mul_left (b : σ → MvPowerSeries τ S) {a : σ → MvPowerSeries τ S} (ha : HasSubst a) : HasSubst (b * a) :=
by
letI : UniformSpace S := ⊥
rw [hasSubst_iff_hasEval_of_discreteTopology] at ha ⊢
exact ha.mul_left b