Proof of Theorem spllen
| Step | Hyp | Ref
| Expression |
| 1 | | spllen.s |
. . . 4
 Word   |
| 2 | | spllen.f |
. . . 4
       |
| 3 | | spllen.t |
. . . 4
           |
| 4 | | spllen.r |
. . . 4
 Word   |
| 5 | | splval 13502 |
. . . 4
  Word 
   
        Word    splice
  
     substr     ++  ++  substr            |
| 6 | 1, 2, 3, 4, 5 | syl13anc 1328 |
. . 3
  splice   
     substr     ++  ++  substr            |
| 7 | 6 | fveq2d 6195 |
. 2
     splice             substr     ++  ++  substr             |
| 8 | | swrdcl 13419 |
. . . . 5
 Word  substr     Word   |
| 9 | 1, 8 | syl 17 |
. . . 4
  substr     Word   |
| 10 | | ccatcl 13359 |
. . . 4
   substr     Word
Word    substr     ++  Word   |
| 11 | 9, 4, 10 | syl2anc 693 |
. . 3
   substr     ++  Word   |
| 12 | | swrdcl 13419 |
. . . 4
 Word  substr         Word   |
| 13 | 1, 12 | syl 17 |
. . 3
  substr        
Word   |
| 14 | | ccatlen 13360 |
. . 3
    substr     ++  Word  substr         Word        substr     ++  ++  substr                 substr
    ++       substr             |
| 15 | 11, 13, 14 | syl2anc 693 |
. 2
       substr     ++  ++  substr                 substr
    ++       substr             |
| 16 | | lencl 13324 |
. . . . . . 7
 Word       |
| 17 | 4, 16 | syl 17 |
. . . . . 6
       |
| 18 | 17 | nn0cnd 11353 |
. . . . 5
       |
| 19 | | elfzelz 12342 |
. . . . . . 7
       |
| 20 | 2, 19 | syl 17 |
. . . . . 6
   |
| 21 | 20 | zcnd 11483 |
. . . . 5
   |
| 22 | 18, 21 | addcld 10059 |
. . . 4
         |
| 23 | | elfzel2 12340 |
. . . . . 6
               |
| 24 | 3, 23 | syl 17 |
. . . . 5
       |
| 25 | 24 | zcnd 11483 |
. . . 4
       |
| 26 | | elfzelz 12342 |
. . . . . 6
           |
| 27 | 3, 26 | syl 17 |
. . . . 5
   |
| 28 | 27 | zcnd 11483 |
. . . 4
   |
| 29 | 22, 25, 28 | addsub12d 10415 |
. . 3
                               |
| 30 | | ccatlen 13360 |
. . . . . 6
   substr     Word
Word       substr
    ++        substr             |
| 31 | 9, 4, 30 | syl2anc 693 |
. . . . 5
      substr
    ++        substr             |
| 32 | | elfzuz 12338 |
. . . . . . . . . 10
           |
| 33 | 2, 32 | syl 17 |
. . . . . . . . 9
       |
| 34 | | eluzfz1 12348 |
. . . . . . . . 9
    
      |
| 35 | 33, 34 | syl 17 |
. . . . . . . 8
       |
| 36 | | elfzuz3 12339 |
. . . . . . . . . . 11
                   |
| 37 | 3, 36 | syl 17 |
. . . . . . . . . 10
           |
| 38 | | elfzuz3 12339 |
. . . . . . . . . . 11
           |
| 39 | 2, 38 | syl 17 |
. . . . . . . . . 10
       |
| 40 | | uztrn 11704 |
. . . . . . . . . 10
              
          |
| 41 | 37, 39, 40 | syl2anc 693 |
. . . . . . . . 9
           |
| 42 | | elfzuzb 12336 |
. . . . . . . . 9
        
                |
| 43 | 33, 41, 42 | sylanbrc 698 |
. . . . . . . 8
           |
| 44 | | swrdlen 13423 |
. . . . . . . 8
  Word
   
             substr          |
| 45 | 1, 35, 43, 44 | syl3anc 1326 |
. . . . . . 7
     substr          |
| 46 | 21 | subid1d 10381 |
. . . . . . 7
     |
| 47 | 45, 46 | eqtrd 2656 |
. . . . . 6
     substr        |
| 48 | 47 | oveq1d 6665 |
. . . . 5
      substr                   |
| 49 | 21, 18 | addcomd 10238 |
. . . . 5
               |
| 50 | 31, 48, 49 | 3eqtrd 2660 |
. . . 4
      substr
    ++           |
| 51 | | elfzuz2 12346 |
. . . . . . 7
                   |
| 52 | 3, 51 | syl 17 |
. . . . . 6
           |
| 53 | | eluzfz2 12349 |
. . . . . 6
                       |
| 54 | 52, 53 | syl 17 |
. . . . 5
               |
| 55 | | swrdlen 13423 |
. . . . 5
  Word
                    
    substr                  |
| 56 | 1, 3, 54, 55 | syl3anc 1326 |
. . . 4
     substr                  |
| 57 | 50, 56 | oveq12d 6668 |
. . 3
       substr
    ++       substr                           |
| 58 | 18, 28, 21 | subsub3d 10422 |
. . . 4
                   |
| 59 | 58 | oveq2d 6666 |
. . 3
                               |
| 60 | 29, 57, 59 | 3eqtr4d 2666 |
. 2
       substr
    ++       substr                           |
| 61 | 7, 15, 60 | 3eqtrd 2660 |
1
     splice                       |