| Step | Hyp | Ref
| Expression |
| 1 | | lencl 11015 |
. . 3
 Word ♯    |
| 2 | | eqeq2 2216 |
. . . . . 6
  ♯  ♯     |
| 3 | 2 | imbi1d 231 |
. . . . 5
   ♯  
 ♯      |
| 4 | 3 | ralbidv 2507 |
. . . 4
  
Word   ♯ 
  Word   ♯      |
| 5 | | eqeq2 2216 |
. . . . . 6
  ♯  ♯     |
| 6 | 5 | imbi1d 231 |
. . . . 5
   ♯  
 ♯      |
| 7 | 6 | ralbidv 2507 |
. . . 4
  
Word   ♯ 
  Word   ♯ 
    |
| 8 | | eqeq2 2216 |
. . . . . 6
    ♯  ♯       |
| 9 | 8 | imbi1d 231 |
. . . . 5
     ♯  
 ♯        |
| 10 | 9 | ralbidv 2507 |
. . . 4
    
Word   ♯ 
  Word   ♯        |
| 11 | | eqeq2 2216 |
. . . . . 6
 ♯ 
 ♯  ♯  ♯     |
| 12 | 11 | imbi1d 231 |
. . . . 5
 ♯ 
  ♯ 

 ♯  ♯      |
| 13 | 12 | ralbidv 2507 |
. . . 4
 ♯ 
 
Word   ♯ 

 Word   ♯  ♯ 
    |
| 14 | | wrdfin 11030 |
. . . . . . 7
 Word   |
| 15 | | fihasheq0 10955 |
. . . . . . 7
  ♯ 
   |
| 16 | 14, 15 | syl 14 |
. . . . . 6
 Word  ♯ 
   |
| 17 | | wrdind.5 |
. . . . . . 7
 |
| 18 | | wrdind.1 |
. . . . . . 7

    |
| 19 | 17, 18 | mpbiri 168 |
. . . . . 6

  |
| 20 | 16, 19 | biimtrdi 163 |
. . . . 5
 Word  ♯ 
   |
| 21 | 20 | rgen 2560 |
. . . 4
 Word   ♯    |
| 22 | | fveqeq2 5597 |
. . . . . . 7
  ♯  ♯     |
| 23 | | wrdind.2 |
. . . . . . 7
     |
| 24 | 22, 23 | imbi12d 234 |
. . . . . 6
   ♯  
 ♯      |
| 25 | 24 | cbvralvw 2743 |
. . . . 5
 
Word   ♯ 

 Word   ♯     |
| 26 | | simprl 529 |
. . . . . . . . . . . . 13
    Word   ♯     Word
♯     
Word   |
| 27 | | fzossfz 10303 |
. . . . . . . . . . . . . 14
 ..^ ♯  
   ♯    |
| 28 | | simprr 531 |
. . . . . . . . . . . . . . . 16
    Word   ♯     Word
♯      ♯      |
| 29 | | nn0p1nn 9349 |
. . . . . . . . . . . . . . . . 17

    |
| 30 | 29 | ad2antrr 488 |
. . . . . . . . . . . . . . . 16
    Word   ♯     Word
♯          |
| 31 | 28, 30 | eqeltrd 2283 |
. . . . . . . . . . . . . . 15
    Word   ♯     Word
♯      ♯    |
| 32 | | fzo0end 10369 |
. . . . . . . . . . . . . . 15
 ♯   ♯    ..^ ♯     |
| 33 | 31, 32 | syl 14 |
. . . . . . . . . . . . . 14
    Word   ♯     Word
♯       ♯    ..^ ♯     |
| 34 | 27, 33 | sselid 3195 |
. . . . . . . . . . . . 13
    Word   ♯     Word
♯       ♯      ♯     |
| 35 | | pfxlen 11156 |
. . . . . . . . . . . . 13
  Word  ♯      ♯    ♯  prefix  ♯      ♯     |
| 36 | 26, 34, 35 | syl2anc 411 |
. . . . . . . . . . . 12
    Word   ♯     Word
♯      ♯  prefix  ♯      ♯     |
| 37 | 28 | oveq1d 5971 |
. . . . . . . . . . . 12
    Word   ♯     Word
♯       ♯         |
| 38 | | nn0cn 9320 |
. . . . . . . . . . . . . 14

  |
| 39 | 38 | ad2antrr 488 |
. . . . . . . . . . . . 13
    Word   ♯     Word
♯     
  |
| 40 | | ax-1cn 8033 |
. . . . . . . . . . . . 13
 |
| 41 | | pncan 8293 |
. . . . . . . . . . . . 13
 
       |
| 42 | 39, 40, 41 | sylancl 413 |
. . . . . . . . . . . 12
    Word   ♯     Word
♯            |
| 43 | 36, 37, 42 | 3eqtrd 2243 |
. . . . . . . . . . 11
    Word   ♯     Word
♯      ♯  prefix  ♯       |
| 44 | | fveqeq2 5597 |
. . . . . . . . . . . . 13
  prefix  ♯     ♯ 
♯  prefix  ♯        |
| 45 | | vex 2776 |
. . . . . . . . . . . . . . 15
 |
| 46 | 45, 23 | sbcie 3037 |
. . . . . . . . . . . . . 14
   ![]. ].](_drbrack.gif)
  |
| 47 | | dfsbcq 3004 |
. . . . . . . . . . . . . 14
  prefix  ♯       ![]. ].](_drbrack.gif)   prefix  ♯     ![]. ].](_drbrack.gif)    |
| 48 | 46, 47 | bitr3id 194 |
. . . . . . . . . . . . 13
  prefix  ♯    
  prefix  ♯     ![]. ].](_drbrack.gif)    |
| 49 | 44, 48 | imbi12d 234 |
. . . . . . . . . . . 12
  prefix  ♯      ♯  
 ♯  prefix  ♯       prefix  ♯     ![]. ].](_drbrack.gif)     |
| 50 | | simplr 528 |
. . . . . . . . . . . 12
    Word   ♯     Word
♯      
Word   ♯ 
   |
| 51 | | lencl 11015 |
. . . . . . . . . . . . . . . 16
 Word ♯    |
| 52 | 51 | nn0zd 9508 |
. . . . . . . . . . . . . . 15
 Word ♯    |
| 53 | | 1zzd 9414 |
. . . . . . . . . . . . . . 15
 Word   |
| 54 | 52, 53 | zsubcld 9515 |
. . . . . . . . . . . . . 14
 Word  ♯     |
| 55 | | pfxclz 11150 |
. . . . . . . . . . . . . 14
  Word  ♯     prefix  ♯    Word   |
| 56 | 54, 55 | mpdan 421 |
. . . . . . . . . . . . 13
 Word  prefix  ♯    Word   |
| 57 | 56 | ad2antrl 490 |
. . . . . . . . . . . 12
    Word   ♯     Word
♯       prefix
 ♯    Word   |
| 58 | 49, 50, 57 | rspcdva 2886 |
. . . . . . . . . . 11
    Word   ♯     Word
♯       ♯  prefix  ♯       prefix  ♯     ![]. ].](_drbrack.gif)    |
| 59 | 43, 58 | mpd 13 |
. . . . . . . . . 10
    Word   ♯     Word
♯        prefix  ♯     ![]. ].](_drbrack.gif)   |
| 60 | 31 | nnge1d 9094 |
. . . . . . . . . . . . 13
    Word   ♯     Word
♯     
♯    |
| 61 | | wrdlenge1n0 11044 |
. . . . . . . . . . . . . 14
 Word 
♯     |
| 62 | 61 | ad2antrl 490 |
. . . . . . . . . . . . 13
    Word   ♯     Word
♯      
♯     |
| 63 | 60, 62 | mpbird 167 |
. . . . . . . . . . . 12
    Word   ♯     Word
♯        |
| 64 | | lswcl 11061 |
. . . . . . . . . . . 12
  Word  lastS    |
| 65 | 26, 63, 64 | syl2anc 411 |
. . . . . . . . . . 11
    Word   ♯     Word
♯      lastS    |
| 66 | | oveq1 5963 |
. . . . . . . . . . . . . 14
  prefix  ♯     ++        prefix  ♯    ++        |
| 67 | 66 | sbceq1d 3007 |
. . . . . . . . . . . . 13
  prefix  ♯       ++       ![]. ].](_drbrack.gif)
   prefix  ♯    ++       ![]. ].](_drbrack.gif)    |
| 68 | 47, 67 | imbi12d 234 |
. . . . . . . . . . . 12
  prefix  ♯        ![]. ].](_drbrack.gif)   ++       ![]. ].](_drbrack.gif) 
  
prefix  ♯     ![]. ].](_drbrack.gif)
   prefix  ♯    ++       ![]. ].](_drbrack.gif)     |
| 69 | | s1eq 11091 |
. . . . . . . . . . . . . . 15
 lastS 
      lastS      |
| 70 | 69 | oveq2d 5972 |
. . . . . . . . . . . . . 14
 lastS 
  prefix  ♯    ++        prefix  ♯    ++   lastS       |
| 71 | 70 | sbceq1d 3007 |
. . . . . . . . . . . . 13
 lastS 
    prefix  ♯    ++       ![]. ].](_drbrack.gif)
   prefix  ♯    ++   lastS      ![]. ].](_drbrack.gif)    |
| 72 | 71 | imbi2d 230 |
. . . . . . . . . . . 12
 lastS 
    prefix  ♯     ![]. ].](_drbrack.gif)
   prefix  ♯    ++       ![]. ].](_drbrack.gif) 
  
prefix  ♯     ![]. ].](_drbrack.gif)
   prefix  ♯    ++   lastS      ![]. ].](_drbrack.gif)     |
| 73 | | wrdind.6 |
. . . . . . . . . . . . 13
  Word
     |
| 74 | 46 | a1i 9 |
. . . . . . . . . . . . 13
  Word
    ![]. ].](_drbrack.gif)
   |
| 75 | | ccatws1cl 11104 |
. . . . . . . . . . . . . 14
  Word
  ++      Word   |
| 76 | | wrdind.3 |
. . . . . . . . . . . . . . 15
  ++      
   |
| 77 | 76 | adantl 277 |
. . . . . . . . . . . . . 14
   Word

 ++
      
   |
| 78 | 75, 77 | sbcied 3039 |
. . . . . . . . . . . . 13
  Word
    ++       ![]. ].](_drbrack.gif)
   |
| 79 | 73, 74, 78 | 3imtr4d 203 |
. . . . . . . . . . . 12
  Word
    ![]. ].](_drbrack.gif)   ++       ![]. ].](_drbrack.gif)    |
| 80 | 68, 72, 79 | vtocl2ga 2843 |
. . . . . . . . . . 11
   prefix  ♯    Word lastS      prefix  ♯     ![]. ].](_drbrack.gif)
   prefix  ♯    ++   lastS      ![]. ].](_drbrack.gif)    |
| 81 | 57, 65, 80 | syl2anc 411 |
. . . . . . . . . 10
    Word   ♯     Word
♯         prefix  ♯     ![]. ].](_drbrack.gif)    prefix
 ♯    ++   lastS      ![]. ].](_drbrack.gif)    |
| 82 | 59, 81 | mpd 13 |
. . . . . . . . 9
    Word   ♯     Word
♯         prefix  ♯    ++   lastS      ![]. ].](_drbrack.gif)   |
| 83 | 14 | ad2antrl 490 |
. . . . . . . . . . . . 13
    Word   ♯     Word
♯     
  |
| 84 | | hashnncl 10957 |
. . . . . . . . . . . . 13
  ♯ 
   |
| 85 | 83, 84 | syl 14 |
. . . . . . . . . . . 12
    Word   ♯     Word
♯       ♯ 
   |
| 86 | 31, 85 | mpbid 147 |
. . . . . . . . . . 11
    Word   ♯     Word
♯        |
| 87 | | pfxlswccat 11184 |
. . . . . . . . . . . 12
  Word    prefix
 ♯    ++   lastS    
  |
| 88 | 87 | eqcomd 2212 |
. . . . . . . . . . 11
  Word    prefix  ♯    ++   lastS       |
| 89 | 26, 86, 88 | syl2anc 411 |
. . . . . . . . . 10
    Word   ♯     Word
♯     
  prefix  ♯    ++   lastS       |
| 90 | | sbceq1a 3012 |
. . . . . . . . . 10
   prefix  ♯    ++   lastS     
   prefix  ♯    ++   lastS      ![]. ].](_drbrack.gif)    |
| 91 | 89, 90 | syl 14 |
. . . . . . . . 9
    Word   ♯     Word
♯      
   prefix  ♯    ++   lastS      ![]. ].](_drbrack.gif)    |
| 92 | 82, 91 | mpbird 167 |
. . . . . . . 8
    Word   ♯     Word
♯        |
| 93 | 92 | expr 375 |
. . . . . . 7
    Word   ♯    Word   ♯   
   |
| 94 | 93 | ralrimiva 2580 |
. . . . . 6
   Word   ♯ 
 
 Word   ♯       |
| 95 | 94 | ex 115 |
. . . . 5

 
Word   ♯ 
  Word   ♯        |
| 96 | 25, 95 | biimtrid 152 |
. . . 4

 
Word   ♯ 
 
Word   ♯        |
| 97 | 4, 7, 10, 13, 21, 96 | nn0ind 9502 |
. . 3
 ♯   Word   ♯  ♯ 
   |
| 98 | 1, 97 | syl 14 |
. 2
 Word  Word   ♯  ♯ 
   |
| 99 | | eqidd 2207 |
. 2
 Word ♯  ♯    |
| 100 | | fveqeq2 5597 |
. . . 4
  ♯  ♯  ♯  ♯     |
| 101 | | wrdind.4 |
. . . 4
     |
| 102 | 100, 101 | imbi12d 234 |
. . 3
   ♯  ♯ 

 ♯  ♯      |
| 103 | 102 | rspcv 2877 |
. 2
 Word  
Word   ♯  ♯    ♯  ♯      |
| 104 | 98, 99, 103 | mp2d 47 |
1
 Word   |