98 lines
2.7 KiB
Nim
98 lines
2.7 KiB
Nim
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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StrategyType* = enum
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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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LinearStrategy,
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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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SteppedStrategy
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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* = object
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strategyType*: StrategyType
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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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iterations*: int # getIndices(iteration) will run from 0 ..< iterations
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step*: int
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func checkIteration(self: IndexingStrategy, iteration: int): void {.raises: [IndexingError].} =
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if iteration >= self.iterations:
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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 iterations.")
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func getIter(first, last, step: int): Iter[int] =
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{.cast(noSideEffect).}:
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Iter[int].new(first, last, step)
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func getLinearIndicies(
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self: IndexingStrategy,
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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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func getSteppedIndicies(
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self: IndexingStrategy,
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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.iterations)
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func getIndicies*(
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self: IndexingStrategy,
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iteration: int): Iter[int] {.raises: [IndexingError].} =
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case self.strategyType
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of StrategyType.LinearStrategy:
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self.getLinearIndicies(iteration)
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of StrategyType.SteppedStrategy:
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self.getSteppedIndicies(iteration)
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func init*(
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strategy: StrategyType,
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firstIndex, lastIndex, iterations: int): IndexingStrategy {.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 iterations <= 0:
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raise newException(
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IndexingWrongIterationsError,
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"iterations (" & $iterations & ") must be greater than zero.")
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IndexingStrategy(
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strategyType: strategy,
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firstIndex: firstIndex,
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lastIndex: lastIndex,
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iterations: iterations,
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step: divUp((lastIndex - firstIndex), iterations))
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