| Some definitions of interest. |
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iseg | Def l1 l2 == l:T List. l2 = (l1 @ l) |
| | Thm* T:Type, l1,l2:T List. l1 l2 Prop |
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append | Def as @ bs == Case of as; nil bs ; a.as' [a / (as' @ bs)] (recursive) |
| | Thm* T:Type, as,bs:T List. (as @ bs) T List |
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firstn | Def firstn(n;as)
Def == Case of as
Def == Canil nil
Def == Caa.as' if 0< n [a / firstn(n-1;as')] else nil fi
Def (recursive) |
| | Thm* A:Type, as:A List, n: . firstn(n;as) A List |
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iff | Def P  Q == (P  Q) & (P  Q) |
| | Thm* A,B:Prop. (A  B) Prop |
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int_seg | Def {i..j } == {k: | i k < j } |
| | Thm* m,n: . {m..n } Type |
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length | Def ||as|| == Case of as; nil 0 ; a.as' ||as'||+1 (recursive) |
| | Thm* A:Type, l:A List. ||l||  |
| | Thm* ||nil||  |