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[feature] stdlib, types: Unfication of runtime types
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| Copyright © 2011 MLstate | ||
| This file is part of OPA. | ||
| OPA is free software: you can redistribute it and/or modify it under the | ||
| terms of the GNU Affero General Public License, version 3, as published by | ||
| the Free Software Foundation. | ||
| OPA is distributed in the hope that it will be useful, but WITHOUT ANY | ||
| WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS | ||
| FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for | ||
| more details. | ||
| You should have received a copy of the GNU Affero General Public License | ||
| along with OPA. If not, see <http://www.gnu.org/licenses/>. | ||
| */ | ||
| /* | ||
| * @author Rudy Sicard 2011 | ||
| */ | ||
|
|
||
| /** | ||
| * Utilities to detect cycle in sequence or recursive computation. | ||
| */ | ||
|
|
||
| /** | ||
| * {1 Interface of a cycle detector implementation} | ||
| */ | ||
| type CycleDetector('t,'elmt) = | ||
| {{ | ||
| empty : 't | ||
| push : 'elmt, 't -> 't | ||
| detected : 't -> bool | ||
| }} | ||
|
|
||
| /** | ||
| * {2 Interface of a cycle detector implementation based on equal function parameter} | ||
| */ | ||
| type CycleDetectorFunctor('t) = {{ | ||
| create : forall('elmt) . ('elmt,'elmt->bool) -> CycleDetector('t,'elmt) | ||
| }} | ||
|
|
||
| /** | ||
| * {3 Implementation based on Toirtoise and Hare algorithm } | ||
| */ | ||
| @abstract | ||
| type TortoiseAndHare.t('a) = | ||
| { | ||
| detected : bool | ||
| tortoise_step : int | ||
| hare : list('a) // last values first | ||
| tortoise : list('a)// first value last | ||
| } | ||
|
|
||
| TortoiseAndHare = {{ | ||
| create(equal:'a,'a->bool) = {{ | ||
| empty = { | ||
| detected = false | ||
| tortoise_step = 0 // so on first push nothing we only fill hare | ||
| hare = [] | ||
| tortoise = [] | ||
| }:TortoiseAndHare.t('a) | ||
|
|
||
| push(h:'a,t:TortoiseAndHare.t('a)):TortoiseAndHare.t('a) = | ||
| old_hare = t.hare | ||
| hare = [h|old_hare] | ||
| tortoise_step = t.tortoise_step+1 | ||
| if Bitwise.land(tortoise_step,1)==0 then ( | ||
| match t.tortoise | ||
| [] -> | ||
| do @assert(old_hare != []) | ||
| push(h,{t with tortoise=List.rev(old_hare) hare = []}) // only case of empty old_hare | ||
| [tor|tortoise] -> | ||
| t = ~{t with tortoise_step hare tortoise} | ||
| if equal(tor,h) then ~{t with detected=true} else t | ||
| ) | ||
| else ~{t with tortoise_step hare} | ||
|
|
||
| detected(t:TortoiseAndHare.t('a)) = t.detected | ||
| }} | ||
| }} : CycleDetectorFunctor |
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