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32 lines
1.3 KiB
Plaintext
32 lines
1.3 KiB
Plaintext
; we extend the array module, now that we have strings
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(defmodule Array
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(doc range "creates an array from `start` to `end` with `step` between them
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(the elements must support `<`, `<=`, `>=`, and `to-int`).
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It returns a `Result.Success` if the input was right, and a `Result.Error` if
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the input given was wrong, containing an error message.")
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(defn range [start end step]
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(cond
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(= step (zero))
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(Result.Error @"`Array.range` cannot be called with step size `0`.")
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(and (< start end) (< step (zero)))
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(Result.Error @"`Array.range` cannot be called with a step size `< 0` and `start < end`.")
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(and (> start end) (> step (zero)))
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(Result.Error @"`Array.range` cannot be called with a step size `> 0` and `start > end`.")
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(let-do [x (allocate (Int.inc (Int.abs (to-int (/ (- end start) step)))))
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e start
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i 0
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op (if (< start end) <= >=)]
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(while (op e end)
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(do
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(aset! &x i e)
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(set! i (Int.inc i))
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(set! e (+ e step))))
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(Result.Success x))))
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(doc range-or-default "is a version of [`range`](#range) that returns an empty
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array on failure.")
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(defn range-or-default [start end step]
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(Result.from-success (range start end step) []))
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)
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