1352 lines
32 KiB
Elixir
1352 lines
32 KiB
Elixir
import Kernel, except: [length: 1]
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defmodule String do
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@moduledoc ~S"""
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A String in Elixir is a UTF-8 encoded binary.
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## String and binary operations
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The functions in this module act according to the
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Unicode Standard, version 6.3.0. For example,
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`capitalize/1`, `downcase/1`, `strip/1` are provided by this
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module.
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In addition to this module, Elixir provides more low-level
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operations that work directly with binaries. Some
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of those can be found in the `Kernel` module, as:
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* `Kernel.binary_part/3` - retrieves part of the binary
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* `Kernel.bit_size/1` and `Kernel.byte_size/1` - size related functions
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* `Kernel.is_bitstring/1` and `Kernel.is_binary/1` - type checking function
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* Plus a number of functions for working with binaries (bytes)
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[in the `:binary` module](http://erlang.org/doc/man/binary.html)
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## Codepoints and graphemes
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As per the Unicode Standard, a codepoint is an Unicode
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Character, which may be represented by one or more bytes.
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For example, the character "é" is represented with two
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bytes:
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iex> byte_size("é")
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2
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However, this module returns the proper length:
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iex> String.length("é")
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1
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Furthermore, this module also presents the concept of
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graphemes, which are multiple characters that may be
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"perceived as a single character" by readers. For example,
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the same "é" character written above could be represented
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by the letter "e" followed by the accent ́:
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iex> string = "\x{0065}\x{0301}"
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iex> byte_size(string)
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3
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iex> String.length(string)
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1
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Although the example above is made of two characters, it is
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perceived by users as one.
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Graphemes can also be two characters that are interpreted
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as one by some languages. For example, some languages may
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consider "ch" as a grapheme. However, since this information
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depends on the locale, it is not taken into account by this
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module.
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In general, the functions in this module rely on the Unicode
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Standard, but does not contain any of the locale specific
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behaviour.
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More information about graphemes can be found in the [Unicode
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Standard Annex #29](http://www.unicode.org/reports/tr29/).
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This current Elixir version implements Extended Grapheme Cluster
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algorithm.
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## Integer codepoints
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Although codepoints could be represented as integers, this
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module represents all codepoints as strings. For example:
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iex> String.codepoints("josé")
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["j", "o", "s", "é"]
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There are a couple of ways to retrieve a character integer
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codepoint. One may use the `?` special macro:
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iex> ?j
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106
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iex> ?é
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233
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Or also via pattern matching:
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iex> << eacute :: utf8 >> = "é"
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iex> eacute
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233
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As we have seen above, codepoints can be inserted into
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a string by their hexadecimal code:
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"jos\x{0065}\x{0301}" #=>
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"josé"
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## Self-synchronization
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The UTF-8 encoding is self-synchronizing. This means that
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if malformed data (i.e., data that is not possible according
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to the definition of the encoding) is encountered, only one
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codepoint needs to be rejected.
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This module relies on this behaviour to ignore such invalid
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characters. For example, `length/1` is going to return
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a correct result even if an invalid codepoint is fed into it.
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In other words, this module expects invalid data to be detected
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when retrieving data from the external source. For example, a
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driver that reads strings from a database will be the one
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responsible to check the validity of the encoding.
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"""
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@type t :: binary
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@type codepoint :: t
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@type grapheme :: t
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@doc """
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Checks if a string is printable considering it is encoded
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as UTF-8. Returns `true` if so, `false` otherwise.
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## Examples
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iex> String.printable?("abc")
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true
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"""
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@spec printable?(t) :: boolean
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def printable?(<< h :: utf8, t :: binary >>)
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when h in ?\040..?\176
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when h in 0xA0..0xD7FF
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when h in 0xE000..0xFFFD
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when h in 0x10000..0x10FFFF do
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printable?(t)
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end
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def printable?(<<?\n, t :: binary>>), do: printable?(t)
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def printable?(<<?\r, t :: binary>>), do: printable?(t)
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def printable?(<<?\t, t :: binary>>), do: printable?(t)
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def printable?(<<?\v, t :: binary>>), do: printable?(t)
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def printable?(<<?\b, t :: binary>>), do: printable?(t)
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def printable?(<<?\f, t :: binary>>), do: printable?(t)
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def printable?(<<?\e, t :: binary>>), do: printable?(t)
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def printable?(<<?\d, t :: binary>>), do: printable?(t)
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def printable?(<<?\a, t :: binary>>), do: printable?(t)
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def printable?(<<>>), do: true
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def printable?(b) when is_binary(b), do: false
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@doc """
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Divides a string into substrings at each Unicode whitespace
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occurrence with leading and trailing whitespace ignored.
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## Examples
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iex> String.split("foo bar")
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["foo", "bar"]
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iex> String.split("foo" <> <<194, 133>> <> "bar")
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["foo", "bar"]
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iex> String.split(" foo bar ")
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["foo", "bar"]
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"""
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@spec split(t) :: [t]
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defdelegate split(binary), to: String.Unicode
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@doc ~S"""
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Divides a string into substrings based on a pattern.
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Returns a list of these substrings. The pattern can
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be a string, a list of strings or a regular expression.
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The string is split into as many parts as possible by
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default, but can be controlled via the `parts: num` option.
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If you pass `parts: :infinity`, it will return all possible parts.
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Empty strings are only removed from the result if the
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`trim` option is set to `true`.
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## Examples
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Splitting with a string pattern:
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iex> String.split("a,b,c", ",")
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["a", "b", "c"]
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iex> String.split("a,b,c", ",", parts: 2)
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["a", "b,c"]
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iex> String.split(" a b c ", " ", trim: true)
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["a", "b", "c"]
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A list of patterns:
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iex> String.split("1,2 3,4", [" ", ","])
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["1", "2", "3", "4"]
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A regular expression:
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iex> String.split("a,b,c", ~r{,})
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["a", "b", "c"]
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iex> String.split("a,b,c", ~r{,}, parts: 2)
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["a", "b,c"]
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iex> String.split(" a b c ", ~r{\s}, trim: true)
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["a", "b", "c"]
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Splitting on empty patterns returns codepoints:
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iex> String.split("abc", ~r{})
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["a", "b", "c", ""]
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iex> String.split("abc", "")
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["a", "b", "c", ""]
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iex> String.split("abc", "", trim: true)
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["a", "b", "c"]
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iex> String.split("abc", "", parts: 2)
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["a", "bc"]
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"""
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@spec split(t, t | [t] | Regex.t) :: [t]
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@spec split(t, t | [t] | Regex.t, Keyword.t) :: [t]
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def split(binary, pattern, options \\ [])
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def split("", _pattern, _options), do: [""]
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def split(binary, "", options), do: split(binary, ~r""u, options)
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def split(binary, pattern, options) do
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if Regex.regex?(pattern) do
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Regex.split(pattern, binary, options)
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else
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splits =
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case Keyword.get(options, :parts, :infinity) do
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num when is_number(num) and num > 0 ->
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split_parts(binary, pattern, num - 1)
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_ ->
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:binary.split(binary, pattern, [:global])
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end
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if Keyword.get(options, :trim, false) do
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for split <- splits, split != "", do: split
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else
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splits
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end
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end
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end
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defp split_parts("", _pattern, _num), do: [""]
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defp split_parts(binary, pattern, num), do: split_parts(binary, pattern, num, [])
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defp split_parts("", _pattern, _num, parts), do: Enum.reverse([""|parts])
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defp split_parts(binary, _pattern, 0, parts), do: Enum.reverse([binary|parts])
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defp split_parts(binary, pattern, num, parts) do
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case :binary.split(binary, pattern) do
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[head] -> Enum.reverse([head|parts])
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[head, rest] -> split_parts(rest, pattern, num - 1, [head|parts])
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end
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end
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@doc """
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Splits a string into two at the specified offset. When the offset given is
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negative, location is counted from the end of the string.
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The offset is capped to the length of the string.
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Returns a tuple with two elements.
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## Examples
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iex> String.split_at "sweetelixir", 5
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{"sweet", "elixir"}
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iex> String.split_at "sweetelixir", -6
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{"sweet", "elixir"}
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iex> String.split_at "abc", 0
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{"", "abc"}
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iex> String.split_at "abc", 1000
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{"abc", ""}
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iex> String.split_at "abc", -1000
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{"", "abc"}
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"""
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@spec split_at(t, integer) :: {t, t}
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def split_at(string, offset)
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def split_at(binary, index) when index == 0, do:
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{"", binary}
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def split_at(binary, index) when index > 0, do:
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do_split_at(next_grapheme(binary), 0, index, "")
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def split_at(binary, index) when index < 0, do:
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do_split_at(next_grapheme(binary), 0, max(0, byte_size(binary)+index), "")
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defp do_split_at(nil, _, _, acc), do:
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{acc, ""}
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defp do_split_at({grapheme, rest}, current_pos, target_pos, acc) when current_pos < target_pos, do:
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do_split_at(next_grapheme(rest), current_pos+1, target_pos, acc <> grapheme)
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defp do_split_at({grapheme, rest}, pos, pos, acc), do:
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{acc, grapheme <> rest}
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@doc """
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Convert all characters on the given string to uppercase.
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## Examples
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iex> String.upcase("abcd")
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"ABCD"
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iex> String.upcase("ab 123 xpto")
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"AB 123 XPTO"
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iex> String.upcase("josé")
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"JOSÉ"
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"""
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@spec upcase(t) :: t
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defdelegate upcase(binary), to: String.Unicode
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@doc """
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Convert all characters on the given string to lowercase.
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## Examples
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iex> String.downcase("ABCD")
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"abcd"
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iex> String.downcase("AB 123 XPTO")
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"ab 123 xpto"
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iex> String.downcase("JOSÉ")
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"josé"
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"""
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@spec downcase(t) :: t
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defdelegate downcase(binary), to: String.Unicode
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@doc """
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Converts the first character in the given string to
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uppercase and the remaining to lowercase.
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This relies on the titlecase information provided
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by the Unicode Standard. Note this function makes
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no attempt to capitalize all words in the string
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(usually known as titlecase).
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## Examples
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iex> String.capitalize("abcd")
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"Abcd"
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iex> String.capitalize("fin")
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"Fin"
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iex> String.capitalize("josé")
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"José"
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"""
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@spec capitalize(t) :: t
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def capitalize(string) when is_binary(string) do
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{char, rest} = String.Unicode.titlecase_once(string)
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char <> downcase(rest)
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end
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@doc """
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Returns a string where trailing Unicode whitespace
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has been removed.
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## Examples
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iex> String.rstrip(" abc ")
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" abc"
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"""
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@spec rstrip(t) :: t
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defdelegate rstrip(binary), to: String.Unicode
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@doc """
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Returns a string where trailing `char` have been removed.
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## Examples
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iex> String.rstrip(" abc _", ?_)
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" abc "
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"""
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@spec rstrip(t, char) :: t
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def rstrip("", _char), do: ""
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# Do a quick check before we traverse the whole
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# binary. :binary.last is a fast operation (it
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# does not traverse the whole binary).
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def rstrip(string, char) when char in 0..127 do
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if :binary.last(string) == char do
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do_rstrip(string, "", char)
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else
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string
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end
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end
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def rstrip(string, char) when is_integer(char) do
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do_rstrip(string, "", char)
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end
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defp do_rstrip(<<char :: utf8, string :: binary>>, buffer, char) do
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<<do_rstrip(string, <<char :: utf8, buffer :: binary>>, char) :: binary>>
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end
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defp do_rstrip(<<char :: utf8, string :: binary>>, buffer, another_char) do
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<<buffer :: binary, char :: utf8, do_rstrip(string, "", another_char) :: binary>>
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end
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defp do_rstrip(<<>>, _, _) do
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<<>>
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end
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@doc """
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Returns a string where leading Unicode whitespace
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has been removed.
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## Examples
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iex> String.lstrip(" abc ")
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"abc "
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"""
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defdelegate lstrip(binary), to: String.Unicode
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@doc """
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Returns a string where leading `char` have been removed.
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## Examples
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iex> String.lstrip("_ abc _", ?_)
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" abc _"
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"""
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@spec lstrip(t, char) :: t
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def lstrip(<<char :: utf8, rest :: binary>>, char) when is_integer(char) do
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<<lstrip(rest, char) :: binary>>
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end
|
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def lstrip(other, char) when is_integer(char) do
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other
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end
|
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|
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@doc """
|
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Returns a string where leading/trailing Unicode whitespace
|
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has been removed.
|
||
|
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## Examples
|
||
|
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iex> String.strip(" abc ")
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"abc"
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"""
|
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@spec strip(t) :: t
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def strip(string) do
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rstrip(lstrip(string))
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end
|
||
|
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@doc """
|
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Returns a string where leading/trailing `char` have been
|
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removed.
|
||
|
||
## Examples
|
||
|
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iex> String.strip("a abc a", ?a)
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" abc "
|
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|
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"""
|
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@spec strip(t, char) :: t
|
||
|
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def strip(string, char) do
|
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rstrip(lstrip(string, char), char)
|
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end
|
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|
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@doc ~S"""
|
||
Returns a new string of length `len` with `subject` right justified and
|
||
padded with `padding`. If `padding` is not present, it defaults to
|
||
whitespace. When `len` is less than the length of `subject`, `subject` is
|
||
returned.
|
||
|
||
## Examples
|
||
|
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iex> String.rjust("abc", 5)
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" abc"
|
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|
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iex> String.rjust("abc", 5, ?-)
|
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"--abc"
|
||
|
||
"""
|
||
@spec rjust(t, pos_integer) :: t
|
||
@spec rjust(t, pos_integer, char) :: t
|
||
|
||
def rjust(subject, len) do
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rjust(subject, len, ?\s)
|
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end
|
||
|
||
def rjust(subject, len, padding) when is_integer(padding) do
|
||
do_justify(subject, len, padding, :right)
|
||
end
|
||
|
||
@doc ~S"""
|
||
Returns a new string of length `len` with `subject` left justified and padded
|
||
with `padding`. If `padding` is not present, it defaults to whitespace. When
|
||
`len` is less than the length of `subject`, `subject` is returned.
|
||
|
||
## Examples
|
||
|
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iex> String.ljust("abc", 5)
|
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"abc "
|
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|
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iex> String.ljust("abc", 5, ?-)
|
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"abc--"
|
||
|
||
"""
|
||
@spec ljust(t, pos_integer) :: t
|
||
@spec ljust(t, pos_integer, char) :: t
|
||
|
||
def ljust(subject, len) do
|
||
ljust(subject, len, ?\s)
|
||
end
|
||
|
||
def ljust(subject, len, padding) when is_integer(padding) do
|
||
do_justify(subject, len, padding, :left)
|
||
end
|
||
|
||
defp do_justify(subject, 0, _padding, _type) do
|
||
subject
|
||
end
|
||
|
||
defp do_justify(subject, len, padding, type) when is_integer(padding) do
|
||
subject_len = length(subject)
|
||
|
||
cond do
|
||
subject_len >= len ->
|
||
subject
|
||
subject_len < len ->
|
||
fill = duplicate(<<padding :: utf8>>, len - subject_len)
|
||
|
||
case type do
|
||
:left -> subject <> fill
|
||
:right -> fill <> subject
|
||
end
|
||
end
|
||
end
|
||
|
||
@doc ~S"""
|
||
Returns a new binary based on `subject` by replacing the parts
|
||
matching `pattern` by `replacement`. By default, it replaces
|
||
all entries, except if the `global` option is set to `false`.
|
||
|
||
A `pattern` may be a string or a regex.
|
||
|
||
## Examples
|
||
|
||
iex> String.replace("a,b,c", ",", "-")
|
||
"a-b-c"
|
||
|
||
iex> String.replace("a,b,c", ",", "-", global: false)
|
||
"a-b,c"
|
||
|
||
The pattern can also be a regex. In those cases, one can give `\N`
|
||
in the `replacement` string to access a specific capture in the regex:
|
||
|
||
iex> String.replace("a,b,c", ~r/,(.)/, ",\\1\\1")
|
||
"a,bb,cc"
|
||
|
||
Notice we had to escape the escape character `\`. By giving `&`,
|
||
one can inject the whole matched pattern in the replacement string.
|
||
|
||
When strings are used as a pattern, a developer can also use the
|
||
replaced part inside the `replacement` via the `:insert_replaced` option:
|
||
|
||
iex> String.replace("a,b,c", "b", "[]", insert_replaced: 1)
|
||
"a,[b],c"
|
||
|
||
iex> String.replace("a,b,c", ",", "[]", insert_replaced: 2)
|
||
"a[],b[],c"
|
||
|
||
iex> String.replace("a,b,c", ",", "[]", insert_replaced: [1, 1])
|
||
"a[,,]b[,,]c"
|
||
|
||
"""
|
||
@spec replace(t, t, t) :: t
|
||
@spec replace(t, t, t, Keyword.t) :: t
|
||
|
||
def replace(subject, pattern, replacement, options \\ []) when is_binary(replacement) do
|
||
if Regex.regex?(pattern) do
|
||
Regex.replace(pattern, subject, replacement, global: options[:global])
|
||
else
|
||
opts = translate_replace_options(options)
|
||
:binary.replace(subject, pattern, replacement, opts)
|
||
end
|
||
end
|
||
|
||
defp translate_replace_options(options) do
|
||
opts = if Keyword.get(options, :global) != false, do: [:global], else: []
|
||
|
||
if insert = Keyword.get(options, :insert_replaced) do
|
||
opts = [{:insert_replaced, insert}|opts]
|
||
end
|
||
|
||
opts
|
||
end
|
||
|
||
@doc """
|
||
Reverses the given string. Works on graphemes.
|
||
|
||
## Examples
|
||
|
||
iex> String.reverse("abcd")
|
||
"dcba"
|
||
|
||
iex> String.reverse("hello world")
|
||
"dlrow olleh"
|
||
|
||
iex> String.reverse("hello ∂og")
|
||
"go∂ olleh"
|
||
|
||
"""
|
||
@spec reverse(t) :: t
|
||
def reverse(string) do
|
||
do_reverse(next_grapheme(string), [])
|
||
end
|
||
|
||
defp do_reverse({grapheme, rest}, acc) do
|
||
do_reverse(next_grapheme(rest), [grapheme|acc])
|
||
end
|
||
|
||
defp do_reverse(nil, acc), do: IO.iodata_to_binary(acc)
|
||
|
||
@doc """
|
||
Returns a binary `subject` duplicated `n` times.
|
||
|
||
## Examples
|
||
|
||
iex> String.duplicate("abc", 0)
|
||
""
|
||
|
||
iex> String.duplicate("abc", 1)
|
||
"abc"
|
||
|
||
iex> String.duplicate("abc", 2)
|
||
"abcabc"
|
||
|
||
"""
|
||
@spec duplicate(t, pos_integer) :: t
|
||
def duplicate(subject, n) when is_integer(n) and n >= 0 do
|
||
:binary.copy(subject, n)
|
||
end
|
||
|
||
@doc """
|
||
Returns all codepoints in the string.
|
||
|
||
## Examples
|
||
|
||
iex> String.codepoints("josé")
|
||
["j", "o", "s", "é"]
|
||
|
||
iex> String.codepoints("оптими зации")
|
||
["о","п","т","и","м","и"," ","з","а","ц","и","и"]
|
||
|
||
iex> String.codepoints("ἅἪῼ")
|
||
["ἅ","Ἢ","ῼ"]
|
||
|
||
"""
|
||
@spec codepoints(t) :: [codepoint]
|
||
defdelegate codepoints(string), to: String.Unicode
|
||
|
||
@doc """
|
||
Returns the next codepoint in a String.
|
||
|
||
The result is a tuple with the codepoint and the
|
||
remaining of the string or `nil` in case
|
||
the string reached its end.
|
||
|
||
As with other functions in the String module, this
|
||
function does not check for the validity of the codepoint.
|
||
That said, if an invalid codepoint is found, it will
|
||
be returned by this function.
|
||
|
||
## Examples
|
||
|
||
iex> String.next_codepoint("josé")
|
||
{"j", "osé"}
|
||
|
||
"""
|
||
@compile {:inline, next_codepoint: 1}
|
||
@spec next_codepoint(t) :: {codepoint, t} | nil
|
||
defdelegate next_codepoint(string), to: String.Unicode
|
||
|
||
@doc ~S"""
|
||
Checks whether `str` contains only valid characters.
|
||
|
||
## Examples
|
||
|
||
iex> String.valid?("a")
|
||
true
|
||
|
||
iex> String.valid?("ø")
|
||
true
|
||
|
||
iex> String.valid?(<<0xffff :: 16>>)
|
||
false
|
||
|
||
iex> String.valid?("asd" <> <<0xffff :: 16>>)
|
||
false
|
||
|
||
"""
|
||
@spec valid?(t) :: boolean
|
||
|
||
noncharacters = Enum.to_list(?\x{FDD0}..?\x{FDEF}) ++
|
||
[ ?\x{0FFFE}, ?\x{0FFFF}, ?\x{1FFFE}, ?\x{1FFFF}, ?\x{2FFFE}, ?\x{2FFFF},
|
||
?\x{3FFFE}, ?\x{3FFFF}, ?\x{4FFFE}, ?\x{4FFFF}, ?\x{5FFFE}, ?\x{5FFFF},
|
||
?\x{6FFFE}, ?\x{6FFFF}, ?\x{7FFFE}, ?\x{7FFFF}, ?\x{8FFFE}, ?\x{8FFFF},
|
||
?\x{9FFFE}, ?\x{9FFFF}, ?\x{10FFFE}, ?\x{10FFFF} ]
|
||
|
||
for noncharacter <- noncharacters do
|
||
def valid?(<< unquote(noncharacter) :: utf8, _ :: binary >>), do: false
|
||
end
|
||
|
||
def valid?(<<_ :: utf8, t :: binary>>), do: valid?(t)
|
||
def valid?(<<>>), do: true
|
||
def valid?(_), do: false
|
||
|
||
@doc ~S"""
|
||
Checks whether `str` is a valid character.
|
||
|
||
All characters are codepoints, but some codepoints
|
||
are not valid characters. They may be reserved, private,
|
||
or other.
|
||
|
||
More info at: http://en.wikipedia.org/wiki/Mapping_of_Unicode_characters#Noncharacters
|
||
|
||
## Examples
|
||
|
||
iex> String.valid_character?("a")
|
||
true
|
||
|
||
iex> String.valid_character?("ø")
|
||
true
|
||
|
||
iex> String.valid_character?("\x{ffff}")
|
||
false
|
||
|
||
"""
|
||
@spec valid_character?(t) :: boolean
|
||
|
||
def valid_character?(<<_ :: utf8>> = codepoint), do: valid?(codepoint)
|
||
def valid_character?(_), do: false
|
||
|
||
@doc ~S"""
|
||
Splits the string into chunks of characters that share a common trait.
|
||
|
||
The trait can be one of two options:
|
||
|
||
* `:valid` – the string is split into chunks of valid and invalid character
|
||
sequences
|
||
|
||
* `:printable` – the string is split into chunks of printable and
|
||
non-printable character sequences
|
||
|
||
Returns a list of binaries each of which contains only one kind of
|
||
characters.
|
||
|
||
If the given string is empty, an empty list is returned.
|
||
|
||
## Examples
|
||
|
||
iex> String.chunk(<<?a, ?b, ?c, 0>>, :valid)
|
||
["abc\000"]
|
||
|
||
iex> String.chunk(<<?a, ?b, ?c, 0, 0x0ffff::utf8>>, :valid)
|
||
["abc\000", <<0x0ffff::utf8>>]
|
||
|
||
iex> String.chunk(<<?a, ?b, ?c, 0, 0x0ffff::utf8>>, :printable)
|
||
["abc", <<0, 0x0ffff::utf8>>]
|
||
|
||
"""
|
||
@spec chunk(t, :valid | :printable) :: [t]
|
||
|
||
def chunk(string, trait)
|
||
|
||
def chunk("", _), do: []
|
||
|
||
def chunk(str, trait) when trait in [:valid, :printable] do
|
||
{cp, _} = next_codepoint(str)
|
||
pred_fn = make_chunk_pred(trait)
|
||
do_chunk(str, pred_fn.(cp), pred_fn)
|
||
end
|
||
|
||
|
||
defp do_chunk(str, flag, pred_fn), do: do_chunk(str, [], <<>>, flag, pred_fn)
|
||
|
||
defp do_chunk(<<>>, acc, <<>>, _, _), do: Enum.reverse(acc)
|
||
|
||
defp do_chunk(<<>>, acc, chunk, _, _), do: Enum.reverse(acc, [chunk])
|
||
|
||
defp do_chunk(str, acc, chunk, flag, pred_fn) do
|
||
{cp, rest} = next_codepoint(str)
|
||
if pred_fn.(cp) != flag do
|
||
do_chunk(rest, [chunk|acc], cp, not flag, pred_fn)
|
||
else
|
||
do_chunk(rest, acc, chunk <> cp, flag, pred_fn)
|
||
end
|
||
end
|
||
|
||
defp make_chunk_pred(:valid), do: &valid?/1
|
||
defp make_chunk_pred(:printable), do: &printable?/1
|
||
|
||
@doc """
|
||
Returns unicode graphemes in the string as per Extended Grapheme
|
||
Cluster algorithm outlined in the [Unicode Standard Annex #29,
|
||
Unicode Text Segmentation](http://www.unicode.org/reports/tr29/).
|
||
|
||
## Examples
|
||
|
||
iex> String.graphemes("Ā̀stute")
|
||
["Ā̀","s","t","u","t","e"]
|
||
|
||
"""
|
||
@spec graphemes(t) :: [grapheme]
|
||
defdelegate graphemes(string), to: String.Graphemes
|
||
|
||
@doc """
|
||
Returns the next grapheme in a String.
|
||
|
||
The result is a tuple with the grapheme and the
|
||
remaining of the string or `nil` in case
|
||
the String reached its end.
|
||
|
||
## Examples
|
||
|
||
iex> String.next_grapheme("josé")
|
||
{"j", "osé"}
|
||
|
||
"""
|
||
@compile {:inline, next_grapheme: 1}
|
||
@spec next_grapheme(t) :: {grapheme, t} | nil
|
||
defdelegate next_grapheme(string), to: String.Graphemes
|
||
|
||
@doc """
|
||
Returns the first grapheme from an utf8 string,
|
||
nil if the string is empty.
|
||
|
||
## Examples
|
||
|
||
iex> String.first("elixir")
|
||
"e"
|
||
|
||
iex> String.first("եոգլի")
|
||
"ե"
|
||
|
||
"""
|
||
@spec first(t) :: grapheme | nil
|
||
def first(string) do
|
||
case next_grapheme(string) do
|
||
{char, _} -> char
|
||
nil -> nil
|
||
end
|
||
end
|
||
|
||
@doc """
|
||
Returns the last grapheme from an utf8 string,
|
||
`nil` if the string is empty.
|
||
|
||
## Examples
|
||
|
||
iex> String.last("elixir")
|
||
"r"
|
||
|
||
iex> String.last("եոգլի")
|
||
"ի"
|
||
|
||
"""
|
||
@spec last(t) :: grapheme | nil
|
||
def last(string) do
|
||
do_last(next_grapheme(string), nil)
|
||
end
|
||
|
||
defp do_last({char, rest}, _) do
|
||
do_last(next_grapheme(rest), char)
|
||
end
|
||
|
||
defp do_last(nil, last_char), do: last_char
|
||
|
||
@doc """
|
||
Returns the number of unicode graphemes in an utf8 string.
|
||
|
||
## Examples
|
||
|
||
iex> String.length("elixir")
|
||
6
|
||
|
||
iex> String.length("եոգլի")
|
||
5
|
||
|
||
"""
|
||
@spec length(t) :: non_neg_integer
|
||
def length(string) do
|
||
do_length(next_grapheme(string))
|
||
end
|
||
|
||
defp do_length({_, rest}) do
|
||
1 + do_length(next_grapheme(rest))
|
||
end
|
||
|
||
defp do_length(nil), do: 0
|
||
|
||
@doc """
|
||
Returns the grapheme in the `position` of the given utf8 `string`.
|
||
If `position` is greater than `string` length, then it returns `nil`.
|
||
|
||
## Examples
|
||
|
||
iex> String.at("elixir", 0)
|
||
"e"
|
||
|
||
iex> String.at("elixir", 1)
|
||
"l"
|
||
|
||
iex> String.at("elixir", 10)
|
||
nil
|
||
|
||
iex> String.at("elixir", -1)
|
||
"r"
|
||
|
||
iex> String.at("elixir", -10)
|
||
nil
|
||
|
||
"""
|
||
@spec at(t, integer) :: grapheme | nil
|
||
|
||
def at(string, position) when position >= 0 do
|
||
do_at(next_grapheme(string), position, 0)
|
||
end
|
||
|
||
def at(string, position) when position < 0 do
|
||
real_pos = length(string) - abs(position)
|
||
case real_pos >= 0 do
|
||
true -> do_at(next_grapheme(string), real_pos, 0)
|
||
false -> nil
|
||
end
|
||
end
|
||
|
||
defp do_at({_ , rest}, desired_pos, current_pos) when desired_pos > current_pos do
|
||
do_at(next_grapheme(rest), desired_pos, current_pos + 1)
|
||
end
|
||
|
||
defp do_at({char, _}, desired_pos, current_pos) when desired_pos == current_pos do
|
||
char
|
||
end
|
||
|
||
defp do_at(nil, _, _), do: nil
|
||
|
||
@doc """
|
||
Returns a substring starting at the offset given by the first, and
|
||
a length given by the second.
|
||
If the offset is greater than string length, then it returns `""`.
|
||
|
||
## Examples
|
||
|
||
iex> String.slice("elixir", 1, 3)
|
||
"lix"
|
||
|
||
iex> String.slice("elixir", 1, 10)
|
||
"lixir"
|
||
|
||
iex> String.slice("elixir", 10, 3)
|
||
""
|
||
|
||
iex> String.slice("elixir", -4, 4)
|
||
"ixir"
|
||
|
||
iex> String.slice("elixir", -10, 3)
|
||
""
|
||
|
||
iex> String.slice("a", 0, 1500)
|
||
"a"
|
||
|
||
iex> String.slice("a", 1, 1500)
|
||
""
|
||
|
||
iex> String.slice("a", 2, 1500)
|
||
""
|
||
|
||
"""
|
||
@spec slice(t, integer, integer) :: grapheme
|
||
|
||
def slice(_, _, 0) do
|
||
""
|
||
end
|
||
|
||
def slice(string, start, len) when start >= 0 and len >= 0 do
|
||
do_slice(next_grapheme(string), start, start + len - 1, 0, "")
|
||
end
|
||
|
||
def slice(string, start, len) when start < 0 and len >= 0 do
|
||
real_start_pos = length(string) - abs(start)
|
||
case real_start_pos >= 0 do
|
||
true -> do_slice(next_grapheme(string), real_start_pos, real_start_pos + len - 1, 0, "")
|
||
false -> ""
|
||
end
|
||
end
|
||
|
||
@doc """
|
||
Returns a substring from the offset given by the start of the
|
||
range to the offset given by the end of the range.
|
||
|
||
If the start of the range is not a valid offset for the given
|
||
string or if the range is in reverse order, returns `""`.
|
||
|
||
## Examples
|
||
|
||
iex> String.slice("elixir", 1..3)
|
||
"lix"
|
||
|
||
iex> String.slice("elixir", 1..10)
|
||
"lixir"
|
||
|
||
iex> String.slice("elixir", 10..3)
|
||
""
|
||
|
||
iex> String.slice("elixir", -4..-1)
|
||
"ixir"
|
||
|
||
iex> String.slice("elixir", 2..-1)
|
||
"ixir"
|
||
|
||
iex> String.slice("elixir", -4..6)
|
||
"ixir"
|
||
|
||
iex> String.slice("elixir", -1..-4)
|
||
""
|
||
|
||
iex> String.slice("elixir", -10..-7)
|
||
""
|
||
|
||
iex> String.slice("a", 0..1500)
|
||
"a"
|
||
|
||
iex> String.slice("a", 1..1500)
|
||
""
|
||
|
||
iex> String.slice("a", 2..1500)
|
||
""
|
||
|
||
"""
|
||
@spec slice(t, Range.t) :: t
|
||
|
||
def slice(string, range)
|
||
|
||
def slice(string, first..last) when first >= 0 and last >= 0 do
|
||
do_slice(next_grapheme(string), first, last, 0, "")
|
||
end
|
||
|
||
def slice(string, first..last) do
|
||
total = length(string)
|
||
|
||
if first < 0 do
|
||
first = total + first
|
||
end
|
||
|
||
if last < 0 do
|
||
last = total + last
|
||
end
|
||
|
||
if first >= 0 do
|
||
do_slice(next_grapheme(string), first, last, 0, "")
|
||
else
|
||
""
|
||
end
|
||
end
|
||
|
||
defp do_slice(_, start_pos, last_pos, _, _) when start_pos > last_pos do
|
||
""
|
||
end
|
||
|
||
defp do_slice({_, rest}, start_pos, last_pos, current_pos, acc) when current_pos < start_pos do
|
||
do_slice(next_grapheme(rest), start_pos, last_pos, current_pos + 1, acc)
|
||
end
|
||
|
||
defp do_slice({char, rest}, start_pos, last_pos, current_pos, acc) when current_pos >= start_pos and current_pos < last_pos do
|
||
do_slice(next_grapheme(rest), start_pos, last_pos, current_pos + 1, acc <> char)
|
||
end
|
||
|
||
defp do_slice({char, _}, start_pos, last_pos, current_pos, acc) when current_pos >= start_pos and current_pos == last_pos do
|
||
acc <> char
|
||
end
|
||
|
||
defp do_slice(nil, _, _, _, acc) do
|
||
acc
|
||
end
|
||
|
||
@doc """
|
||
Returns `true` if `string` starts with any of the prefixes given, otherwise
|
||
`false`. `prefixes` can be either a single prefix or a list of prefixes.
|
||
|
||
## Examples
|
||
|
||
iex> String.starts_with? "elixir", "eli"
|
||
true
|
||
|
||
iex> String.starts_with? "elixir", ["erlang", "elixir"]
|
||
true
|
||
|
||
iex> String.starts_with? "elixir", ["erlang", "ruby"]
|
||
false
|
||
|
||
"""
|
||
@spec starts_with?(t, t | [t]) :: boolean
|
||
|
||
def starts_with?(string, prefixes) when is_list(prefixes) do
|
||
Enum.any?(prefixes, &do_starts_with(string, &1))
|
||
end
|
||
|
||
def starts_with?(string, prefix) do
|
||
do_starts_with(string, prefix)
|
||
end
|
||
|
||
defp do_starts_with(string, "") when is_binary(string) do
|
||
true
|
||
end
|
||
|
||
defp do_starts_with(string, prefix) when is_binary(prefix) do
|
||
Kernel.match?({0, _}, :binary.match(string, prefix))
|
||
end
|
||
|
||
@doc """
|
||
Returns `true` if `string` ends with any of the suffixes given, otherwise
|
||
`false`. `suffixes` can be either a single suffix or a list of suffixes.
|
||
|
||
## Examples
|
||
|
||
iex> String.ends_with? "language", "age"
|
||
true
|
||
|
||
iex> String.ends_with? "language", ["youth", "age"]
|
||
true
|
||
|
||
iex> String.ends_with? "language", ["youth", "elixir"]
|
||
false
|
||
|
||
"""
|
||
@spec ends_with?(t, t | [t]) :: boolean
|
||
|
||
def ends_with?(string, suffixes) when is_list(suffixes) do
|
||
Enum.any?(suffixes, &do_ends_with(string, &1))
|
||
end
|
||
|
||
def ends_with?(string, suffix) do
|
||
do_ends_with(string, suffix)
|
||
end
|
||
|
||
defp do_ends_with(string, "") when is_binary(string) do
|
||
true
|
||
end
|
||
|
||
defp do_ends_with(string, suffix) when is_binary(suffix) do
|
||
string_size = byte_size(string)
|
||
suffix_size = byte_size(suffix)
|
||
scope = {string_size - suffix_size, suffix_size}
|
||
(suffix_size <= string_size) and (:nomatch != :binary.match(string, suffix, [scope: scope]))
|
||
end
|
||
|
||
@doc """
|
||
Check if `string` matches the given regular expression.
|
||
|
||
## Examples
|
||
|
||
iex> String.match?("foo", ~r/foo/)
|
||
true
|
||
|
||
iex> String.match?("bar", ~r/foo/)
|
||
false
|
||
|
||
"""
|
||
@spec match?(t, Regex.t) :: boolean
|
||
def match?(string, regex) do
|
||
Regex.match?(regex, string)
|
||
end
|
||
|
||
@doc """
|
||
Check if `string` contains any of the given `contents`.
|
||
|
||
`matches` can be either a single string or a list of strings.
|
||
|
||
## Examples
|
||
|
||
iex> String.contains? "elixir of life", "of"
|
||
true
|
||
|
||
iex> String.contains? "elixir of life", ["life", "death"]
|
||
true
|
||
|
||
iex> String.contains? "elixir of life", ["death", "mercury"]
|
||
false
|
||
|
||
"""
|
||
@spec contains?(t, t | [t]) :: boolean
|
||
|
||
def contains?(string, contents) when is_list(contents) do
|
||
Enum.any?(contents, &do_contains(string, &1))
|
||
end
|
||
|
||
def contains?(string, content) do
|
||
do_contains(string, content)
|
||
end
|
||
|
||
defp do_contains(string, "") when is_binary(string) do
|
||
true
|
||
end
|
||
|
||
defp do_contains(string, match) when is_binary(match) do
|
||
:nomatch != :binary.match(string, match)
|
||
end
|
||
|
||
@doc """
|
||
Converts a string into a char list.
|
||
|
||
## Examples
|
||
|
||
iex> String.to_char_list("æß")
|
||
'æß'
|
||
|
||
Notice that this function expect a list of integer representing
|
||
UTF-8 codepoints. If you have a raw binary, you must instead use
|
||
[the `:binary` module](http://erlang.org/doc/man/binary.html).
|
||
"""
|
||
@spec to_char_list(t) :: char_list
|
||
def to_char_list(string) when is_binary(string) do
|
||
case :unicode.characters_to_list(string) do
|
||
result when is_list(result) ->
|
||
result
|
||
|
||
{:error, encoded, rest} ->
|
||
raise UnicodeConversionError, encoded: encoded, rest: rest, kind: :invalid
|
||
|
||
{:incomplete, encoded, rest} ->
|
||
raise UnicodeConversionError, encoded: encoded, rest: rest, kind: :incomplete
|
||
end
|
||
end
|
||
|
||
@doc """
|
||
Converts a string to an atom.
|
||
|
||
Currently Elixir does not support conversions from strings
|
||
which contains Unicode codepoints greater than 0xFF.
|
||
|
||
Inlined by the compiler.
|
||
|
||
## Examples
|
||
|
||
iex> String.to_atom("my_atom")
|
||
:my_atom
|
||
|
||
"""
|
||
@spec to_atom(String.t) :: atom
|
||
def to_atom(string) do
|
||
:erlang.binary_to_atom(string, :utf8)
|
||
end
|
||
|
||
@doc """
|
||
Converts a string to an existing atom.
|
||
|
||
Currently Elixir does not support conversions from strings
|
||
which contains Unicode codepoints greater than 0xFF.
|
||
|
||
Inlined by the compiler.
|
||
|
||
## Examples
|
||
|
||
iex> :my_atom
|
||
iex> String.to_existing_atom("my_atom")
|
||
:my_atom
|
||
|
||
iex> String.to_existing_atom("this_atom_will_never_exist")
|
||
** (ArgumentError) argument error
|
||
|
||
"""
|
||
@spec to_existing_atom(String.t) :: atom
|
||
def to_existing_atom(string) do
|
||
:erlang.binary_to_existing_atom(string, :utf8)
|
||
end
|
||
|
||
@doc """
|
||
Returns a integer whose text representation is `string`.
|
||
|
||
Inlined by the compiler.
|
||
|
||
## Examples
|
||
|
||
iex> String.to_integer("123")
|
||
123
|
||
|
||
"""
|
||
@spec to_integer(String.t) :: integer
|
||
def to_integer(string) do
|
||
:erlang.binary_to_integer(string)
|
||
end
|
||
|
||
@doc """
|
||
Returns an integer whose text representation is `string` in base `base`.
|
||
|
||
Inlined by the compiler.
|
||
|
||
## Examples
|
||
|
||
iex> String.to_integer("3FF", 16)
|
||
1023
|
||
|
||
"""
|
||
@spec to_integer(String.t, pos_integer) :: integer
|
||
def to_integer(string, base) do
|
||
:erlang.binary_to_integer(string, base)
|
||
end
|
||
|
||
@doc """
|
||
Returns a float whose text representation is `string`.
|
||
|
||
Inlined by the compiler.
|
||
|
||
## Examples
|
||
|
||
iex> String.to_float("2.2017764e+0")
|
||
2.2017764
|
||
|
||
"""
|
||
@spec to_float(String.t) :: float
|
||
def to_float(string) do
|
||
:erlang.binary_to_float(string)
|
||
end
|
||
end
|