Metamath Proof Explorer


Theorem chnsuslle

Description: Length of a subsequence is bounded by the length of original chain. (Contributed by Ender Ting, 30-Jan-2026)

Ref Expression
Hypotheses chnsubseq.1
|- ( ph -> W e. ( .< Chain A ) )
chnsubseq.2
|- ( ph -> I e. ( < Chain ( 0 ..^ ( # ` W ) ) ) )
chnsubseq.3
|- ( ph -> .< Po A )
Assertion chnsuslle
|- ( ph -> ( # ` ( W o. I ) ) <_ ( # ` W ) )

Proof

Step Hyp Ref Expression
1 chnsubseq.1
 |-  ( ph -> W e. ( .< Chain A ) )
2 chnsubseq.2
 |-  ( ph -> I e. ( < Chain ( 0 ..^ ( # ` W ) ) ) )
3 chnsubseq.3
 |-  ( ph -> .< Po A )
4 ltso
 |-  < Or RR
5 sopo
 |-  ( < Or RR -> < Po RR )
6 4 5 mp1i
 |-  ( ph -> < Po RR )
7 fzossz
 |-  ( 0 ..^ ( # ` W ) ) C_ ZZ
8 zssre
 |-  ZZ C_ RR
9 7 8 sstri
 |-  ( 0 ..^ ( # ` W ) ) C_ RR
10 9 a1i
 |-  ( ph -> ( 0 ..^ ( # ` W ) ) C_ RR )
11 poss
 |-  ( ( 0 ..^ ( # ` W ) ) C_ RR -> ( < Po RR -> < Po ( 0 ..^ ( # ` W ) ) ) )
12 10 11 syl
 |-  ( ph -> ( < Po RR -> < Po ( 0 ..^ ( # ` W ) ) ) )
13 6 12 mpd
 |-  ( ph -> < Po ( 0 ..^ ( # ` W ) ) )
14 ovexd
 |-  ( ph -> ( 0 ..^ ( # ` W ) ) e. _V )
15 13 2 14 chnpolleha
 |-  ( ph -> ( # ` I ) <_ ( # ` ( 0 ..^ ( # ` W ) ) ) )
16 1 2 chnsubseqwl
 |-  ( ph -> ( # ` ( W o. I ) ) = ( # ` I ) )
17 1 chnwrd
 |-  ( ph -> W e. Word A )
18 lencl
 |-  ( W e. Word A -> ( # ` W ) e. NN0 )
19 17 18 syl
 |-  ( ph -> ( # ` W ) e. NN0 )
20 hashfzo0
 |-  ( ( # ` W ) e. NN0 -> ( # ` ( 0 ..^ ( # ` W ) ) ) = ( # ` W ) )
21 19 20 syl
 |-  ( ph -> ( # ` ( 0 ..^ ( # ` W ) ) ) = ( # ` W ) )
22 21 eqcomd
 |-  ( ph -> ( # ` W ) = ( # ` ( 0 ..^ ( # ` W ) ) ) )
23 15 16 22 3brtr4d
 |-  ( ph -> ( # ` ( W o. I ) ) <_ ( # ` W ) )