Created
November 9, 2017 19:34
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Idris勉強会で出た疑問
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| -- ref: https://github.com/idris-lang/Idris-dev/blob/0d3d2d66796b172e9933360aee51993a4abc624d/test/totality006/totality006.idr | |
| import Data.So | |
| antitrue : So False -> a | |
| antitrue Oh impossible | |
| total | |
| eqNat : (n : Nat) -> (m : Nat) -> So (n == m) -> (n = m) | |
| eqNat Z Z Oh = Refl | |
| eqNat (S k) Z um = antitrue um -- なぜここでimpossibleが出来ない？ | |
| eqNat Z (S k) um = antitrue um | |
| eqNat (S k) (S l) um = cong $ eqNat k l um -- なぜumが使える？型が違うはずでは？？ | |
| total | |
| gtNat : (a:Nat) -> (b:Nat) -> So (a > b) -> GT a b | |
| gtNat Z Z Oh impossible | |
| gtNat Z (S k) um = antitrue um | |
| gtNat (S k) Z um = LTESucc LTEZero | |
| gtNat (S k) (S j) um = LTESucc $ gtNat k j ?um -- どうやって?umを作る？with?? | |
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um : S n == S m は == の定義から um : n == m に簡約される模様