Description: Obsolete version of ccat2s1fst as of 28-Jan-2024. The first symbol of the concatenation of a word with two single symbols. (Contributed by Alexander van der Vekens, 22-Sep-2018) (New usage is discouraged.) (Proof modification is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | ccat2s1fstOLD | |- ( ( ( W e. Word V /\ 0 < ( # ` W ) ) /\ ( X e. V /\ Y e. V ) ) -> ( ( ( W ++ <" X "> ) ++ <" Y "> ) ` 0 ) = ( W ` 0 ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0nn0 | |- 0 e. NN0 |
|
2 | ccat2s1fvwOLD | |- ( ( ( W e. Word V /\ 0 e. NN0 /\ 0 < ( # ` W ) ) /\ ( X e. V /\ Y e. V ) ) -> ( ( ( W ++ <" X "> ) ++ <" Y "> ) ` 0 ) = ( W ` 0 ) ) |
|
3 | 1 2 | mp3anl2 | |- ( ( ( W e. Word V /\ 0 < ( # ` W ) ) /\ ( X e. V /\ Y e. V ) ) -> ( ( ( W ++ <" X "> ) ++ <" Y "> ) ` 0 ) = ( W ` 0 ) ) |