Theorem s2s2

Description: Concatenation of fixed length strings. (Contributed by Mario Carneiro, 26-Feb-2016)

	Ref	Expression
Assertion	s2s2	|- <" A B C D "> = ( <" A B "> ++ <" C D "> )

Proof

Step	Hyp	Ref	Expression
1		df-s2	|- <" C D "> = ( <" C "> ++ <" D "> )
2		s2cli	|- <" A B "> e. Word _V
3		s1cli	|- <" C "> e. Word _V
4		df-s4	|- <" A B C D "> = ( <" A B C "> ++ <" D "> )
5		df-s3	|- <" A B C "> = ( <" A B "> ++ <" C "> )
6	1 2 3 4 5	cats1cat	|- <" A B C D "> = ( <" A B "> ++ <" C D "> )