Alexei Sholik
5b2ae4a274
This reverts commit d859057ae93558bdd4a31e31c53bc359c5d41a44. Discussion: https://github.com/elixir-lang/elixir/pull/250#issuecomment-5172536
84 lines
2.0 KiB
Elixir
84 lines
2.0 KiB
Elixir
import Elixir.Builtin, except: [access: 2]
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defprotocol Access do
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@only [List, BitString, Record, Tuple, Atom, Function]
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def access(element, qualifier)
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end
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defimpl Access, for: Tuple do
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def access(tuple, integer) when is_integer(integer) and integer > 0 and integer <= size(tuple) do
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:erlang.element(integer, tuple)
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end
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def access(tuple, integer) when is_integer(integer) and integer < 0 do
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size = size(tuple)
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position = integer + size + 1
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if position > size or position < 1,
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do: nil, else: :erlang.element(position, tuple)
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end
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def access(_tuple, integer) when is_integer(integer) do
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nil
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end
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end
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defimpl Access, for: List do
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## Atom
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def access(list, atom) when is_atom(atom) do
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atom_access(list, atom)
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end
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## Regex
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def access(list, re) when is_regex(re) do
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case Erlang.re.run(list, Regex.re_pattern(re), [{ :capture, :first, :list }]) do
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match: :nomatch
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nil
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match: { :match, [result] }
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result
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end
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end
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## Helpers
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defp atom_access([{k, _}|_], key) when key < k, do: nil
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defp atom_access([{k, _}|d], key) when key > k, do: atom_access(d, key)
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defp atom_access([{_k, value}|_], _key), do: value
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defp atom_access([], _), do: nil
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end
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defimpl Access, for: BitString do
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## Regex
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def access(binary, re) when is_binary(binary) and is_regex(re) do
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case Erlang.re.run(binary, Regex.re_pattern(re), [{ :capture, :first, :binary }]) do
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match: :nomatch
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nil
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match: { :match, [result] }
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result
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end
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end
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end
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defimpl Access, for: Atom do
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@doc """
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An atom access can only be done via keywords. We assume the
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atom represents a record module that implements new and
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receives keywords as argument.
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"""
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def access(atom, keywords) when is_list(keywords) do
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atom.new(keywords)
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end
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end
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defimpl Access, for: Function do
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@doc """
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A function access simply executes it passing the
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the access item as argument.
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"""
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def access(function, item) do
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function.(item)
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end
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end
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