43 lines
1.4 KiB
Text
43 lines
1.4 KiB
Text
/-
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Copyright (c) 2020 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Leonardo de Moura
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-/
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prelude
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import Init.LeanInit
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namespace Std
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-- We put `Range` in `Init` because we want the notation `[i:j]` without importing `Std`
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-- We don't put `Range` in the top-level namespace to avoid collisions with user defined types
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structure Range :=
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(start : Nat := 0)
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(stop : Nat)
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(step : Nat := 1)
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namespace Range
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universes u v
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@[inline] def forIn {β : Type u} {m : Type u → Type v} [Monad m] (range : Range) (init : β) (f : Nat → β → m (ForInStep β)) : m β :=
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let rec @[specialize] loop (i : Nat) (j : Nat) (b : β) : m β := do
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if j ≥ range.stop then
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pure b
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else match i with
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| 0 => pure b
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| i+1 => match ← f j b with
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| ForInStep.done b => pure b
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| ForInStep.yield b => loop i (j + range.step) b
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loop range.stop range.start init
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syntax:max "[" ":" term "]" : term
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syntax:max "[" term ":" term "]" : term
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syntax:max "[" ":" term ":" term "]" : term
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syntax:max "[" term ":" term ":" term "]" : term
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macro_rules
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| `([ : $stop]) => `({ stop := $stop : Range })
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| `([ $start : $stop ]) => `({ start := $start, stop := $stop : Range })
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| `([ $start : $stop : $step ]) => `({ start := $start, stop := $stop, step := $step : Range })
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| `([ : $stop : $step ]) => `({ stop := $stop, step := $step : Range })
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end Range
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end Std
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