4eefc41b6e
We want to make sure string users do not depend on the string implementation. This is the first step. We need this refactoring *now* to make sure it will not be super painful to address issue #1175
101 lines
2.4 KiB
Text
101 lines
2.4 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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structure string :=
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(data : list char)
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def list.as_string (s : list char) : string :=
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⟨s.reverse⟩
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namespace string
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def empty : string :=
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⟨list.nil⟩
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instance : inhabited string :=
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⟨empty⟩
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def length : string → nat
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| ⟨s⟩ := s.length
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instance : has_sizeof string :=
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⟨string.length⟩
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def str : string → char → string
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| ⟨s⟩ c := ⟨c::s⟩
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def append : string → string → string
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| ⟨a⟩ ⟨b⟩ := ⟨b ++ a⟩
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def is_empty : string → bool
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| ⟨[]⟩ := tt
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| _ := ff
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instance : has_append string :=
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⟨string.append⟩
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def to_list : string → list char
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| ⟨s⟩ := s.reverse
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def pop_back : string → string
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| ⟨s⟩ := ⟨s.tail⟩
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def popn_back : string → nat → string
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| ⟨s⟩ n := ⟨s.dropn n⟩
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def intercalate (s : string) (ss : list string) : string :=
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(list.intercalate s.to_list (ss.map to_list)).as_string
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def fold {α} (a : α) (f : α → char → α) (s : string) : α :=
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s.to_list.foldl f a
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def front (s : string) : char :=
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s.to_list.head
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def back : string → char
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| ⟨[]⟩ := default char
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| ⟨c::cs⟩ := c
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def backn : string → nat → string
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| ⟨s⟩ n := ⟨s.taken n⟩
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def join (l : list string) : string :=
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l.foldl (λ r s, r ++ s) ""
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end string
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open list string
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private def utf8_length_aux : nat → nat → list char → 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 string.utf8_length : string → nat
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| s := utf8_length_aux 0 0 s.to_list
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export string (utf8_length)
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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.to_list 0
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def char.to_string (c : char) : string :=
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str empty c
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