Thm* 
Alph,St:Type, C:NComp(Alph;St). ||C|| 
0 ; a.as' ||as'||+1 (recursive)
Thm* A:Type, l:A*. ||l||
Thm* ||nil||
| nd_comp_length |
Def ||C|| == ||C||
Thm* |
| length |
Def ||as|| == Case of as; nil 0 ; a.as' ||as'||+1 (recursive)
Thm*
Thm* ||nil|| |
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