} == {k:
| i 
k < j }
m,n:. {m..n} 
Type
0 ; a.as' ||as'||+1 (recursive)A:Type, l:A List. ||l|| 
== {i:| 0i } TypeA:Type, l:A List, n:. 0n 
n < ||l|| l[n] A| Some definitions of interest. | |
| int_seg | Def {i..j} == {k:| i k < j } |
| Thm* m,n:. {m..n} Type | |
| length | Def ||as|| == Case of as; nil 0 ; a.as' ||as'||+1 (recursive) |
| Thm* A:Type, l:A List. ||l|| | |
| Thm* ||nil|| | |
| nat | Def == {i:| 0i } |
| Thm* Type | |
| select | Def l[i] == hd(nth_tl(i;l)) |
| Thm* A:Type, l:A List, n:. 0n n < ||l|| l[n] A |
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