a0a8103804
This suggestion has been discussed at Slack. We have decided to use #"c" as notation because we wanted to allow `'` in the beginning of identifiers like in SML and F*. In particular, we wanted to allow users to use 'a 'b 'c for naming type parameters like in SML. However, nobody used this notation. In the Lean standard library, we are using greek letters for naming type parameters. So, there is no real motivation for the ugly #"c" syntax.
54 lines
1.5 KiB
Text
54 lines
1.5 KiB
Text
/-
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Copyright (c) 2016 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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Author: Leonardo de Moura
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-/
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prelude
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import init.data.list.basic
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import init.data.char.basic
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def string := list char
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namespace string
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@[pattern] def empty : string := list.nil
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instance : inhabited string :=
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⟨empty⟩
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instance : has_sizeof string :=
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⟨list.sizeof⟩
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@[pattern] def str : char → string → string := list.cons
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def concat (a b : string) : string :=
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list.append b a
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instance : has_append string :=
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⟨string.concat⟩
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end string
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open list
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private def utf8_length_aux : nat → nat → string → nat
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| 0 r (c::s) :=
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let n := char.to_nat c in
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if n < 0x80 then utf8_length_aux 0 (r+1) s
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else if 0xC0 ≤ n ∧ n < 0xE0 then utf8_length_aux 1 (r+1) s
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else if 0xE0 ≤ n ∧ n < 0xF0 then utf8_length_aux 2 (r+1) s
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else if 0xF0 ≤ n ∧ n < 0xF8 then utf8_length_aux 3 (r+1) s
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else if 0xF8 ≤ n ∧ n < 0xFC then utf8_length_aux 4 (r+1) s
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else if 0xFC ≤ n ∧ n < 0xFE then utf8_length_aux 5 (r+1) s
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else utf8_length_aux 0 (r+1) s
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| (n+1) r (c::s) := utf8_length_aux n r s
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| n r [] := r
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def utf8_length : string → nat
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| s := utf8_length_aux 0 0 (reverse s)
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private def to_nat_core : list char → nat → nat
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| [] r := r
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| (c::cs) r :=
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to_nat_core cs (char.to_nat c - char.to_nat '0' + r*10)
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def string.to_nat (s : string) : nat :=
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to_nat_core s.reverse 0
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