62 lines
2.2 KiB
Nim
62 lines
2.2 KiB
Nim
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import std/sequtils
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import ./utils
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# I'm choosing to use an assert here because:
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# 1. These are a programmer errors and *should not* happen during application runtime.
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# 2. Users don't have to deal with Result types.
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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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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 assertIteration(self: IndexingStrategy, iteration: int): void =
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if iteration >= self.numberOfIterations:
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raiseAssert("Indexing iteration can't be greater than or equal to numberOfIterations.")
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method getIndicies*(self: IndexingStrategy, iteration: int): seq[int] {.base.} =
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raiseAssert("Not implemented")
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proc new*(T: type IndexingStrategy, firstIndex, lastIndex, numberOfIterations: int): T =
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if firstIndex > lastIndex:
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raiseAssert("firstIndex (" & $firstIndex & ") can't be greater than lastIndex (" & $lastIndex & ")")
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if numberOfIterations <= 0:
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raiseAssert("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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)
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method getIndicies*(self: LinearIndexingStrategy, iteration: int): seq[int] =
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self.assertIteration(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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toSeq(countup(first, last, 1))
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method getIndicies*(self: SteppedIndexingStrategy, iteration: int): seq[int] =
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self.assertIteration(iteration)
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toSeq(countup(self.firstIndex + iteration, self.lastIndex, self.numberOfIterations))
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