Metamath Proof Explorer

Theorem s4cli

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

Ref Expression
Assertion s4cli 
|- <" A B C D "> e. Word _V

Proof

Step Hyp Ref Expression
1 df-s4 
 |-  <" A B C D "> = ( <" A B C "> ++ <" D "> )
2 s3cli 
 |-  <" A B C "> e. Word _V
3 1 2 cats1cli 
 |-  <" A B C D "> e. Word _V