107 lines
2.8 KiB
Nim
107 lines
2.8 KiB
Nim
import std/sequtils
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import ./errors
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import ./utils
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import ./utils/asynciter
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{.push raises: [].}
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type
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# Representing a strategy for grouping indices (of blocks usually)
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# Given an interation-count as input, will produce a seq of
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# selected indices.
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IndexingError* = object of CodexError
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IndexingWrongIndexError* = object of IndexingError
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IndexingWrongIterationsError* = object of IndexingError
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IndexingStrategy* = ref object of RootObj
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firstIndex*: int # Lowest index that can be returned
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lastIndex*: int # Highest index that can be returned
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numberOfIterations*: int # getIndices(iteration) will run from 0 ..< numberOfIterations
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step*: int
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# Simplest approach:
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# 0 => 0, 1, 2
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# 1 => 3, 4, 5
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# 2 => 6, 7, 8
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LinearIndexingStrategy* = ref object of IndexingStrategy
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# Stepped indexing:
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# 0 => 0, 3, 6
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# 1 => 1, 4, 7
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# 2 => 2, 5, 8
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SteppedIndexingStrategy* = ref object of IndexingStrategy
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proc checkIteration(
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self: IndexingStrategy,
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iteration: int): void {.raises: [IndexingError].} =
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if iteration >= self.numberOfIterations:
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raise newException(
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IndexingError,
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"Indexing iteration can't be greater than or equal to numberOfIterations.")
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method getIndicies*(
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self: IndexingStrategy,
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iteration: int): Iter[int] {.base, raises: [IndexingError].} =
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raiseAssert("Not implemented")
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proc getIter(first, last, step: int): Iter[int] =
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var
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finish = false
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cur = first
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proc get(): int =
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result = cur
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cur += step
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if cur > last:
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finish = true
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proc isFinished(): bool =
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finish
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Iter.new(get, isFinished)
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method getIndicies*(
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self: LinearIndexingStrategy,
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iteration: int): Iter[int] {.raises: [IndexingError].} =
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self.checkIteration(iteration)
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let
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first = self.firstIndex + iteration * (self.step + 1)
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last = min(first + self.step, self.lastIndex)
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getIter(first, last, 1)
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method getIndicies*(
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self: SteppedIndexingStrategy,
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iteration: int): Iter[int] {.raises: [IndexingError].} =
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self.checkIteration(iteration)
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let
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first = self.firstIndex + iteration
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last = self.lastIndex
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getIter(first, last, self.numberOfIterations)
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proc new*(
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T: type IndexingStrategy,
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firstIndex, lastIndex, numberOfIterations: int): T {.raises: [IndexingError].} =
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if firstIndex > lastIndex:
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raise newException(
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IndexingWrongIndexError,
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"firstIndex (" & $firstIndex & ") can't be greater than lastIndex (" & $lastIndex & ")")
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if numberOfIterations <= 0:
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raise newException(
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IndexingWrongIterationsError,
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"numberOfIteration (" & $numberOfIterations & ") must be greater than zero.")
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T(
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firstIndex: firstIndex,
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lastIndex: lastIndex,
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numberOfIterations: numberOfIterations,
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step: divUp((lastIndex - firstIndex), numberOfIterations))
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