Theorem s4cli

Description: A length 4 string is a word. (Contributed by Mario Carneiro, 26-Feb-2016)

	Ref	Expression
Assertion	s4cli	$$⊢⟨“ABCD”⟩\in \mathrm{Word}\mathrm{V}$$

Proof

Step	Hyp	Ref	Expression
1		df-s4	$$⊢⟨“ABCD”⟩=⟨“ABC”⟩\mathrm{++}⟨“D”⟩$$
2		s3cli	$$⊢⟨“ABC”⟩\in \mathrm{Word}\mathrm{V}$$
3	1 2	cats1cli	$$⊢⟨“ABCD”⟩\in \mathrm{Word}\mathrm{V}$$