| Some definitions of interest. | |
| gt | Def i > j == j < i |
| Thm* | |
| int_seg | Def {i..j |
| Thm* | |
| length | Def ||as|| == Case of as; nil |
| Thm* | |
| Thm* ||nil|| | |
| nat | Def |
| Thm* | |
| select | Def l[i] == hd(nth_tl(i;l)) |
| Thm* | |
| sum | Def sum(f(x) | x < k) == primrec(k;0; |
| Thm* |
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