View Source String (Elixir v1.10.3)
Strings in Elixir are UTF-8 encoded binaries.
Strings in Elixir are a sequence of Unicode characters,
typically written between double quoted strings, such
as "hello" and "héllò".
In case a string must have a double-quote in itself,
the double quotes must be escaped with a backslash,
for example: "this is a string with \"double quotes\"".
You can concatenate two strings with the <>/2 operator:
iex> "hello" <> " " <> "world"
"hello world"Interpolation
Strings in Elixir also support interpolation. This allows
you to place some value in the middle of a string by using
the #{} syntax:
iex> name = "joe"
iex> "hello #{name}"
"hello joe"Any Elixir expression is valid inside the interpolation.
If a string is given, the string is interpolated as is.
If any other value is given, Elixir will attempt to convert
it to a string using the String.Chars protocol. This
allows, for example, to output an integer from the interpolation:
iex> "2 + 2 = #{2 + 2}"
"2 + 2 = 4"In case the value you want to interpolate cannot be converted to a string, because it doesn't have an human textual representation, a protocol error will be raised.
Escape characters
Besides allowing double-quotes to be escaped with a backslash, strings also support the following escape characters:
\a- Bell\b- Backspace\t- Horizontal tab\n- Line feed (New lines)\v- Vertical tab\f- Form feed\r- Carriage return\e- Command Escape\#- Returns the#character itself, skipping interpolation\xNN- A byte represented by the hexadecimalNN\uNNNN- A Unicode code point represented byNNNN
Note it is generally not advised to use \xNN in Elixir
strings, as introducing an invalid byte sequence would
make the string invalid. If you have to introduce a
character by its hexdecimal representation, it is best
to work with Unicode code points, such as \uNNNN. In fact,
understanding Unicode code points can be essential when doing
low-level manipulations of string, so let's explore them in
detail next.
Code points and grapheme cluster
The functions in this module act according to the Unicode Standard, version 12.1.0.
As per the standard, a code point is a single Unicode Character, which may be represented by one or more bytes.
For example, although the code point "é" is a single character, its underlying representation uses two bytes:
iex> String.length("é")
1
iex> byte_size("é")
2Furthermore, this module also presents the concept of grapheme cluster (from now on referenced as graphemes). Graphemes can consist of multiple code points that may be perceived as a single character by readers. For example, "é" can be represented either as a single "e with acute" code point or as the letter "e" followed by a "combining acute accent" (two code points):
iex> string = "\u0065\u0301"
iex> byte_size(string)
3
iex> String.length(string)
1
iex> String.codepoints(string)
["e", "́"]
iex> String.graphemes(string)
["é"]Although the example above is made of two characters, it is perceived by users as one.
Graphemes can also be two characters that are interpreted as one by some languages. For example, some languages may consider "ch" as a single character. However, since this information depends on the locale, it is not taken into account by this module.
In general, the functions in this module rely on the Unicode Standard, but do not contain any of the locale specific behaviour. More information about graphemes can be found in the Unicode Standard Annex #29.
For converting a binary to a different encoding and for Unicode
normalization mechanisms, see Erlang's :unicode module.
String and binary operations
To act according to the Unicode Standard, many functions in this module run in linear time, as they need to traverse the whole string considering the proper Unicode code points.
For example, String.length/1 will take longer as
the input grows. On the other hand, Kernel.byte_size/1 always runs
in constant time (i.e. regardless of the input size).
This means often there are performance costs in using the functions in this module, compared to the more low-level operations that work directly with binaries:
Kernel.binary_part/3- retrieves part of the binaryKernel.bit_size/1andKernel.byte_size/1- size related functionsKernel.is_bitstring/1andKernel.is_binary/1- type-check function- Plus a number of functions for working with binaries (bytes)
in the
:binarymodule
There are many situations where using the String module can
be avoided in favor of binary functions or pattern matching.
For example, imagine you have a string prefix and you want to
remove this prefix from another string named full.
One may be tempted to write:
iex> take_prefix = fn full, prefix ->
...> base = String.length(prefix)
...> String.slice(full, base, String.length(full) - base)
...> end
iex> take_prefix.("Mr. John", "Mr. ")
"John"Although the function above works, it performs poorly. To
calculate the length of the string, we need to traverse it
fully, so we traverse both prefix and full strings, then
slice the full one, traversing it again.
A first attempt at improving it could be with ranges:
iex> take_prefix = fn full, prefix ->
...> base = String.length(prefix)
...> String.slice(full, base..-1)
...> end
iex> take_prefix.("Mr. John", "Mr. ")
"John"While this is much better (we don't traverse full twice),
it could still be improved. In this case, since we want to
extract a substring from a string, we can use Kernel.byte_size/1
and Kernel.binary_part/3 as there is no chance we will slice in
the middle of a code point made of more than one byte:
iex> take_prefix = fn full, prefix ->
...> base = byte_size(prefix)
...> binary_part(full, base, byte_size(full) - base)
...> end
iex> take_prefix.("Mr. John", "Mr. ")
"John"Or simply use pattern matching:
iex> take_prefix = fn full, prefix ->
...> base = byte_size(prefix)
...> <<_::binary-size(base), rest::binary>> = full
...> rest
...> end
iex> take_prefix.("Mr. John", "Mr. ")
"John"On the other hand, if you want to dynamically slice a string
based on an integer value, then using String.slice/3 is the
best option as it guarantees we won't incorrectly split a valid
code point into multiple bytes.
Integer code points
Although code points could be represented as integers, this module represents all code points as strings. For example:
iex> String.codepoints("olá")
["o", "l", "á"]There are a couple of ways to retrieve a character integer
code point. One may use the ? construct:
iex> ?o
111
iex> ?á
225Or also via pattern matching:
iex> <<aacute::utf8>> = "á"
iex> aacute
225As we have seen above, code points can be inserted into a string by their hexadecimal code:
iex> "ol\u00E1"
"olá"Finally, to convert a String into a list of integers
code points, usually known as "char lists", you can call
Strig.to_charlist:
iex> String.to_charlist("olá")
[111, 108, 225]Self-synchronization
The UTF-8 encoding is self-synchronizing. This means that if malformed data (i.e., data that is not possible according to the definition of the encoding) is encountered, only one code point needs to be rejected.
This module relies on this behaviour to ignore such invalid
characters. For example, length/1 will return
a correct result even if an invalid code point is fed into it.
In other words, this module expects invalid data to be detected
elsewhere, usually when retrieving data from the external source.
For example, a driver that reads strings from a database will be
responsible to check the validity of the encoding. String.chunk/2
can be used for breaking a string into valid and invalid parts.
Compile binary patterns
Many functions in this module work with patterns. For example,
String.split/2 can split a string into multiple strings given
a pattern. This pattern can be a string, a list of strings or
a compiled pattern:
iex> String.split("foo bar", " ")
["foo", "bar"]
iex> String.split("foo bar!", [" ", "!"])
["foo", "bar", ""]
iex> pattern = :binary.compile_pattern([" ", "!"])
iex> String.split("foo bar!", pattern)
["foo", "bar", ""]The compiled pattern is useful when the same match will be done over and over again. Note though that the compiled pattern cannot be stored in a module attribute as the pattern is generated at runtime and does not survive compile time.
Link to this section Summary
Types
A single Unicode code point encoded in UTF-8. It may be one or more bytes.
Multiple code points that may be perceived as a single character by readers
A UTF-8 encoded binary.
Functions
Returns the grapheme at the position of the given UTF-8 string.
If position is greater than string length, then it returns nil.
Computes the bag distance between two strings.
Converts the first character in the given string to
uppercase and the remainder to lowercase according to mode.
Splits the string into chunks of characters that share a common trait.
Returns all code points in the string.
Checks if string contains any of the given contents.
Converts all characters in the given string to lowercase according to mode.
Returns a string subject duplicated n times.
Returns true if string ends with any of the suffixes given.
Returns true if string1 is canonically equivalent to 'string2'.
Returns the first grapheme from a UTF-8 string,
nil if the string is empty.
Returns Unicode graphemes in the string as per Extended Grapheme Cluster algorithm.
Computes the Jaro distance (similarity) between two strings.
Returns the last grapheme from a UTF-8 string,
nil if the string is empty.
Returns the number of Unicode graphemes in a UTF-8 string.
Checks if string matches the given regular expression.
Returns a keyword list that represents an edit script.
Returns the next code point in a string.
Returns the next grapheme in a string.
Returns the size of the next grapheme.
Converts all characters in string to Unicode normalization
form identified by form.
Returns a new string padded with a leading filler
which is made of elements from the padding.
Returns a new string padded with a trailing filler
which is made of elements from the padding.
Checks if a string contains only printable characters up to character_limit.
Returns a new string created by replacing occurrences of pattern in
subject with replacement.
Replaces all leading occurrences of match by replacement of match in string.
Replaces prefix in string by replacement if it matches match.
Replaces suffix in string by replacement if it matches match.
Replaces all trailing occurrences of match by replacement in string.
Reverses the graphemes in given string.
Returns a substring from the offset given by the start of the range to the offset given by the end of the range.
Returns a substring starting at the offset start, and of
length len.
Divides a string into substrings at each Unicode whitespace occurrence with leading and trailing whitespace ignored. Groups of whitespace are treated as a single occurrence. Divisions do not occur on non-breaking whitespace.
Divides a string into parts based on a pattern.
Splits a string into two at the specified offset. When the offset given is negative, location is counted from the end of the string.
Returns an enumerable that splits a string on demand.
Returns true if string starts with any of the prefixes given.
Converts a string to an atom.
Converts a string into a charlist.
Converts a string to an existing atom.
Returns a float whose text representation is string.
Returns an integer whose text representation is string.
Returns an integer whose text representation is string in base base.
Returns a string where all leading and trailing Unicode whitespaces have been removed.
Returns a string where all leading and trailing to_trim characters have been
removed.
Returns a string where all leading Unicode whitespaces have been removed.
Returns a string where all leading to_trim characters have been removed.
Returns a string where all trailing Unicode whitespaces has been removed.
Returns a string where all trailing to_trim characters have been removed.
Converts all characters in the given string to uppercase according to mode.
Checks whether string contains only valid characters.
Link to this section Types
@type codepoint() :: t()
A single Unicode code point encoded in UTF-8. It may be one or more bytes.
@type grapheme() :: t()
Multiple code points that may be perceived as a single character by readers
@type pattern() :: t() | [t()] | :binary.cp()
@type t() :: binary()
A UTF-8 encoded binary.
The types String.t() and binary() are equivalent to analysis tools.
Although, for those reading the documentation, String.t() implies
it is a UTF-8 encoded binary.
Link to this section Functions
Returns the grapheme at the position of the given UTF-8 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)
nilComputes the bag distance between two strings.
Returns a float value between 0 and 1 representing the bag
distance between string1 and string2.
The bag distance is meant to be an efficient approximation of the distance between two strings to quickly rule out strings that are largely different.
The algorithm is outlined in the "String Matching with Metric Trees Using an Approximate Distance" paper by Ilaria Bartolini, Paolo Ciaccia, and Marco Patella.
Examples
iex> String.bag_distance("abc", "")
0.0
iex> String.bag_distance("abcd", "a")
0.25
iex> String.bag_distance("abcd", "ab")
0.5
iex> String.bag_distance("abcd", "abc")
0.75
iex> String.bag_distance("abcd", "abcd")
1.0Converts the first character in the given string to
uppercase and the remainder to lowercase according to mode.
mode may be :default, :ascii or :greek. The :default mode considers
all non-conditional transformations outlined in the Unicode standard. :ascii
lowercases only the letters A to Z. :greek includes the context sensitive
mappings found in Greek.
Examples
iex> String.capitalize("abcd")
"Abcd"
iex> String.capitalize("fin")
"Fin"
iex> String.capitalize("olá")
"Olá"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\0"]
iex> String.chunk(<<?a, ?b, ?c, 0, 0xFFFF::utf16>>, :valid)
["abc\0", <<0xFFFF::utf16>>]
iex> String.chunk(<<?a, ?b, ?c, 0, 0x0FFFF::utf8>>, :printable)
["abc", <<0, 0x0FFFF::utf8>>]Returns all code points in the string.
For details about code points and graphemes, see the String module documentation.
Examples
iex> String.codepoints("olá")
["o", "l", "á"]
iex> String.codepoints("оптими зации")
["о", "п", "т", "и", "м", "и", " ", "з", "а", "ц", "и", "и"]
iex> String.codepoints("ἅἪῼ")
["ἅ", "Ἢ", "ῼ"]
iex> String.codepoints("é")
["é"]
iex> String.codepoints("é")
["e", "́"]Checks if string contains any of the given contents.
contents can be either a string, a list of strings,
or a compiled pattern.
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"])
falseThe argument can also be a compiled pattern:
iex> pattern = :binary.compile_pattern(["life", "death"])
iex> String.contains?("elixir of life", pattern)
trueAn empty string will always match:
iex> String.contains?("elixir of life", "")
true
iex> String.contains?("elixir of life", ["", "other"])
trueBe aware that this function can match within or across grapheme boundaries.
For example, take the grapheme "é" which is made of the characters
"e" and the acute accent. The following returns true:
iex> String.contains?(String.normalize("é", :nfd), "e")
trueHowever, if "é" is represented by the single character "e with acute"
accent, then it will return false:
iex> String.contains?(String.normalize("é", :nfc), "e")
falseConverts all characters in the given string to lowercase according to mode.
mode may be :default, :ascii or :greek. The :default mode considers
all non-conditional transformations outlined in the Unicode standard. :ascii
lowercases only the letters A to Z. :greek includes the context sensitive
mappings found in Greek.
Examples
iex> String.downcase("ABCD")
"abcd"
iex> String.downcase("AB 123 XPTO")
"ab 123 xpto"
iex> String.downcase("OLÁ")
"olá"The :ascii mode ignores Unicode characters and provides a more
performant implementation when you know the string contains only
ASCII characters:
iex> String.downcase("OLÁ", :ascii)
"olÁ"And :greek properly handles the context sensitive sigma in Greek:
iex> String.downcase("ΣΣ")
"σσ"
iex> String.downcase("ΣΣ", :greek)
"σς"@spec duplicate(t(), non_neg_integer()) :: t()
Returns a string subject duplicated n times.
Inlined by the compiler.
Examples
iex> String.duplicate("abc", 0)
""
iex> String.duplicate("abc", 1)
"abc"
iex> String.duplicate("abc", 2)
"abcabc"Returns true if string ends with any of the suffixes given.
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"])
falseAn empty suffix will always match:
iex> String.ends_with?("language", "")
true
iex> String.ends_with?("language", ["", "other"])
trueReturns true if string1 is canonically equivalent to 'string2'.
It performs Normalization Form Canonical Decomposition (NFD) on the strings before comparing them. This function is equivalent to:
String.normalize(string1, :nfd) == String.normalize(string2, :nfd)If you plan to compare multiple strings, multiple times in a row, you may normalize them upfront and compare them directly to avoid multiple normalization passes.
Examples
iex> String.equivalent?("abc", "abc")
true
iex> String.equivalent?("man\u0303ana", "mañana")
true
iex> String.equivalent?("abc", "ABC")
false
iex> String.equivalent?("nø", "nó")
falseReturns the first grapheme from a UTF-8 string,
nil if the string is empty.
Examples
iex> String.first("elixir")
"e"
iex> String.first("եոգլի")
"ե"Returns Unicode graphemes in the string as per Extended Grapheme Cluster algorithm.
The algorithm is outlined in the Unicode Standard Annex #29, Unicode Text Segmentation.
For details about code points and graphemes, see the String module documentation.
Examples
iex> String.graphemes("Ńaïve")
["Ń", "a", "ï", "v", "e"]
iex> String.graphemes("\u00e9")
["é"]
iex> String.graphemes("\u0065\u0301")
["é"]Computes the Jaro distance (similarity) between two strings.
Returns a float value between 0.0 (equates to no similarity) and 1.0
(is an exact match) representing Jaro
distance between string1 and string2.
The Jaro distance metric is designed and best suited for short
strings such as person names. Elixir itself uses this function
to provide the "did you mean?" functionality. For instance, when you
are calling a function in a module and you have a typo in the
function name, we attempt to suggest the most similar function
name available, if any, based on the jaro_distance/2 score.
Examples
iex> String.jaro_distance("Dwayne", "Duane")
0.8222222222222223
iex> String.jaro_distance("even", "odd")
0.0
iex> String.jaro_distance("same", "same")
1.0Returns the last grapheme from a UTF-8 string,
nil if the string is empty.
Examples
iex> String.last("elixir")
"r"
iex> String.last("եոգլի")
"ի"@spec length(t()) :: non_neg_integer()
Returns the number of Unicode graphemes in a UTF-8 string.
Examples
iex> String.length("elixir")
6
iex> String.length("եոգլի")
5Checks if string matches the given regular expression.
Examples
iex> String.match?("foo", ~r/foo/)
true
iex> String.match?("bar", ~r/foo/)
falseReturns a keyword list that represents an edit script.
Check List.myers_difference/2 for more information.
Examples
iex> string1 = "fox hops over the dog"
iex> string2 = "fox jumps over the lazy cat"
iex> String.myers_difference(string1, string2)
[eq: "fox ", del: "ho", ins: "jum", eq: "ps over the ", del: "dog", ins: "lazy cat"]Returns the next code point in a string.
The result is a tuple with the code point and the
remainder of the string or nil in case
the string reached its end.
As with other functions in the String module, next_codepoint/1
works with binaries that are invalid UTF-8. If the string starts
with a sequence of bytes that is not valid in UTF-8 encoding, the
first element of the returned tuple is a binary with the first byte.
Examples
iex> String.next_codepoint("olá")
{"o", "lá"}
iex> invalid = "\x80\x80OK" # first two bytes are invalid in UTF-8
iex> {_, rest} = String.next_codepoint(invalid)
{<<128>>, <<128, 79, 75>>}
iex> String.next_codepoint(rest)
{<<128>>, "OK"}Comparison with binary pattern matching
Binary pattern matching provides a similar way to decompose a string:
iex> <<codepoint::utf8, rest::binary>> = "Elixir"
"Elixir"
iex> codepoint
69
iex> rest
"lixir"though not entirely equivalent because codepoint comes as
an integer, and the pattern won't match invalid UTF-8.
Binary pattern matching, however, is simpler and more efficient, so pick the option that better suits your use case.
Returns the next grapheme in a string.
The result is a tuple with the grapheme and the
remainder of the string or nil in case
the String reached its end.
Examples
iex> String.next_grapheme("olá")
{"o", "lá"}@spec next_grapheme_size(t()) :: {pos_integer(), t()} | nil
Returns the size of the next grapheme.
The result is a tuple with the next grapheme size and
the remainder of the string or nil in case the string
reached its end.
Examples
iex> String.next_grapheme_size("olá")
{1, "lá"}Converts all characters in string to Unicode normalization
form identified by form.
Invalid Unicode codepoints are skipped and the remaining of
the string is converted. If you want the algorith to stop
and return on invalid codepoint, use :unicode.characters_to_nfd_binary/1
and :unicode.characters_to_nfc_binary/1 instead.
Forms
The supported forms are:
:nfd- Normalization Form Canonical Decomposition. Characters are decomposed by canonical equivalence, and multiple combining characters are arranged in a specific order.:nfc- Normalization Form Canonical Composition. Characters are decomposed and then recomposed by canonical equivalence.
Examples
iex> String.normalize("yêṩ", :nfd)
"yêṩ"
iex> String.normalize("leña", :nfc)
"leña"@spec pad_leading(t(), non_neg_integer(), t() | [t()]) :: t()
Returns a new string padded with a leading filler
which is made of elements from the padding.
Passing a list of strings as padding will take one element of the list
for every missing entry. If the list is shorter than the number of inserts,
the filling will start again from the beginning of the list.
Passing a string padding is equivalent to passing the list of graphemes in it.
If no padding is given, it defaults to whitespace.
When count is less than or equal to the length of string,
given string is returned.
Raises ArgumentError if the given padding contains a non-string element.
Examples
iex> String.pad_leading("abc", 5)
" abc"
iex> String.pad_leading("abc", 4, "12")
"1abc"
iex> String.pad_leading("abc", 6, "12")
"121abc"
iex> String.pad_leading("abc", 5, ["1", "23"])
"123abc"@spec pad_trailing(t(), non_neg_integer(), t() | [t()]) :: t()
Returns a new string padded with a trailing filler
which is made of elements from the padding.
Passing a list of strings as padding will take one element of the list
for every missing entry. If the list is shorter than the number of inserts,
the filling will start again from the beginning of the list.
Passing a string padding is equivalent to passing the list of graphemes in it.
If no padding is given, it defaults to whitespace.
When count is less than or equal to the length of string,
given string is returned.
Raises ArgumentError if the given padding contains a non-string element.
Examples
iex> String.pad_trailing("abc", 5)
"abc "
iex> String.pad_trailing("abc", 4, "12")
"abc1"
iex> String.pad_trailing("abc", 6, "12")
"abc121"
iex> String.pad_trailing("abc", 5, ["1", "23"])
"abc123"@spec printable?(t(), 0) :: true
@spec printable?(t(), pos_integer() | :infinity) :: boolean()
Checks if a string contains only printable characters up to character_limit.
Takes an optional character_limit as a second argument. If character_limit is 0, this
function will return true.
Examples
iex> String.printable?("abc")
true
iex> String.printable?("abc" <> <<0>>)
false
iex> String.printable?("abc" <> <<0>>, 2)
true
iex> String.printable?("abc" <> <<0>>, 0)
trueReturns a new string created by replacing occurrences of pattern in
subject with replacement.
The subject is always a string.
The pattern may be a string, a regular expression, or a compiled pattern.
The replacement may be a string or a function that receives the matched
pattern and must return the replacement as a string or iodata.
By default it replaces all occurrences but this behaviour can be controlled
through the :global option; see the "Options" section below.
Options
:global- (boolean) iftrue, all occurrences ofpatternare replaced withreplacement, otherwise only the first occurrence is replaced. Defaults totrue
Examples
iex> String.replace("a,b,c", ",", "-")
"a-b-c"
iex> String.replace("a,b,c", ",", "-", global: false)
"a-b,c"The pattern may also be a list of strings and the replacement may also be a function that receives the matches:
iex> String.replace("a,b,c", ["a", "c"], fn <<char>> -> <<char + 1>> end)
"b,b,d"When the pattern is a regular expression, one can give \N or
\g{N} in the replacement string to access a specific capture in the
regular expression:
iex> String.replace("a,b,c", ~r/,(.)/, ",\\1\\g{1}")
"a,bb,cc"Notice we had to escape the backslash escape character (i.e., we used \\N
instead of just \N to escape the backslash; same thing for \\g{N}). By
giving \0, one can inject the whole match in the replacement string.
A compiled pattern can also be given:
iex> pattern = :binary.compile_pattern(",")
iex> String.replace("a,b,c", pattern, "[]")
"a[]b[]c"When an empty string is provided as a pattern, the function will treat it as
an implicit empty string between each grapheme and the string will be
interspersed. If an empty string is provided as replacement the subject
will be returned:
iex> String.replace("ELIXIR", "", ".")
".E.L.I.X.I.R."
iex> String.replace("ELIXIR", "", "")
"ELIXIR"Replaces all leading occurrences of match by replacement of match in string.
Returns the string untouched if there are no occurrences.
If match is "", this function raises an ArgumentError exception: this
happens because this function replaces all the occurrences of match at
the beginning of string, and it's impossible to replace "multiple"
occurrences of "".
Examples
iex> String.replace_leading("hello world", "hello ", "")
"world"
iex> String.replace_leading("hello hello world", "hello ", "")
"world"
iex> String.replace_leading("hello world", "hello ", "ola ")
"ola world"
iex> String.replace_leading("hello hello world", "hello ", "ola ")
"ola ola world"Replaces prefix in string by replacement if it matches match.
Returns the string untouched if there is no match. If match is an empty
string (""), replacement is just prepended to string.
Examples
iex> String.replace_prefix("world", "hello ", "")
"world"
iex> String.replace_prefix("hello world", "hello ", "")
"world"
iex> String.replace_prefix("hello hello world", "hello ", "")
"hello world"
iex> String.replace_prefix("world", "hello ", "ola ")
"world"
iex> String.replace_prefix("hello world", "hello ", "ola ")
"ola world"
iex> String.replace_prefix("hello hello world", "hello ", "ola ")
"ola hello world"
iex> String.replace_prefix("world", "", "hello ")
"hello world"Replaces suffix in string by replacement if it matches match.
Returns the string untouched if there is no match. If match is an empty
string (""), replacement is just appended to string.
Examples
iex> String.replace_suffix("hello", " world", "")
"hello"
iex> String.replace_suffix("hello world", " world", "")
"hello"
iex> String.replace_suffix("hello world world", " world", "")
"hello world"
iex> String.replace_suffix("hello", " world", " mundo")
"hello"
iex> String.replace_suffix("hello world", " world", " mundo")
"hello mundo"
iex> String.replace_suffix("hello world world", " world", " mundo")
"hello world mundo"
iex> String.replace_suffix("hello", "", " world")
"hello world"Replaces all trailing occurrences of match by replacement in string.
Returns the string untouched if there are no occurrences.
If match is "", this function raises an ArgumentError exception: this
happens because this function replaces all the occurrences of match at
the end of string, and it's impossible to replace "multiple" occurrences of
"".
Examples
iex> String.replace_trailing("hello world", " world", "")
"hello"
iex> String.replace_trailing("hello world world", " world", "")
"hello"
iex> String.replace_trailing("hello world", " world", " mundo")
"hello mundo"
iex> String.replace_trailing("hello world world", " world", " mundo")
"hello mundo mundo"Reverses the graphemes in given string.
Examples
iex> String.reverse("abcd")
"dcba"
iex> String.reverse("hello world")
"dlrow olleh"
iex> String.reverse("hello ∂og")
"go∂ olleh"Keep in mind reversing the same string twice does not necessarily yield the original string:
iex> "̀e"
"̀e"
iex> String.reverse("̀e")
"è"
iex> String.reverse(String.reverse("̀e"))
"è"In the first example the accent is before the vowel, so it is considered two graphemes. However, when you reverse it once, you have the vowel followed by the accent, which becomes one grapheme. Reversing it again will keep it as one single grapheme.
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 "".
If the start or end of the range is negative, the whole string is traversed first in order to convert the negative indices into positive ones.
Remember this function works with Unicode graphemes and considers
the slices to represent grapheme offsets. If you want to split
on raw bytes, check Kernel.binary_part/3 instead.
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)
""@spec slice(t(), integer(), non_neg_integer()) :: grapheme()
Returns a substring starting at the offset start, and of
length len.
If the offset is greater than string length, then it returns "".
Remember this function works with Unicode graphemes and considers
the slices to represent grapheme offsets. If you want to split
on raw bytes, check Kernel.binary_part/3 instead.
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)
""Divides a string into substrings at each Unicode whitespace occurrence with leading and trailing whitespace ignored. Groups of whitespace are treated as a single occurrence. Divisions do not occur on non-breaking whitespace.
Examples
iex> String.split("foo bar")
["foo", "bar"]
iex> String.split("foo" <> <<194, 133>> <> "bar")
["foo", "bar"]
iex> String.split(" foo bar ")
["foo", "bar"]
iex> String.split("no\u00a0break")
["no\u00a0break"]Divides a string into parts based on a pattern.
Returns a list of these parts. The pattern can be a string, a list of strings, a regular expression, or a compiled pattern.
The string is split into as many parts as possible by
default, but can be controlled via the :parts option.
Empty strings are only removed from the result if the
:trim option is set to true.
When the pattern used is a regular expression, the string is
split using Regex.split/3.
Options
:parts(positive integer or:infinity) - the string is split into at most as many parts as this option specifies. If:infinity, the string will be split into all possible parts. Defaults to:infinity.:trim(boolean) - iftrue, empty strings are removed from the resulting list.
This function also accepts all options accepted by Regex.split/3
if pattern is a regular expression.
Examples
Splitting with a string pattern:
iex> String.split("a,b,c", ",")
["a", "b", "c"]
iex> String.split("a,b,c", ",", parts: 2)
["a", "b,c"]
iex> String.split(" a b c ", " ", trim: true)
["a", "b", "c"]A list of patterns:
iex> String.split("1,2 3,4", [" ", ","])
["1", "2", "3", "4"]A regular expression:
iex> String.split("a,b,c", ~r{,})
["a", "b", "c"]
iex> String.split("a,b,c", ~r{,}, parts: 2)
["a", "b,c"]
iex> String.split(" a b c ", ~r{\s}, trim: true)
["a", "b", "c"]
iex> String.split("abc", ~r{b}, include_captures: true)
["a", "b", "c"]A compiled pattern:
iex> pattern = :binary.compile_pattern([" ", ","])
iex> String.split("1,2 3,4", pattern)
["1", "2", "3", "4"]Splitting on empty string returns graphemes:
iex> String.split("abc", "")
["", "a", "b", "c", ""]
iex> String.split("abc", "", trim: true)
["a", "b", "c"]
iex> String.split("abc", "", parts: 1)
["abc"]
iex> String.split("abc", "", parts: 3)
["", "a", "bc"]Be aware that this function can split within or across grapheme boundaries. For example, take the grapheme "é" which is made of the characters "e" and the acute accent. The following will split the string into two parts:
iex> String.split(String.normalize("é", :nfd), "e")
["", "́"]However, if "é" is represented by the single character "e with acute" accent, then it will split the string into just one part:
iex> String.split(String.normalize("é", :nfc), "e")
["é"]Splits a string into two at the specified offset. When the offset given is negative, location is counted from the end of the string.
The offset is capped to the length of the string. Returns a tuple with two elements.
Note: keep in mind this function splits on graphemes and for such it
has to linearly traverse the string. If you want to split a string or
a binary based on the number of bytes, use Kernel.binary_part/3
instead.
Examples
iex> String.split_at("sweetelixir", 5)
{"sweet", "elixir"}
iex> String.split_at("sweetelixir", -6)
{"sweet", "elixir"}
iex> String.split_at("abc", 0)
{"", "abc"}
iex> String.split_at("abc", 1000)
{"abc", ""}
iex> String.split_at("abc", -1000)
{"", "abc"}@spec splitter(t(), pattern(), keyword()) :: Enumerable.t()
Returns an enumerable that splits a string on demand.
This is in contrast to split/3 which splits the
entire string upfront.
This function does not support regular expressions by design. When using regular expressions, it is often more efficient to have the regular expressions traverse the string at once than in parts, like this function does.
Options
- :trim - when
true, does not emit empty patterns
Examples
iex> String.splitter("1,2 3,4 5,6 7,8,...,99999", [" ", ","]) |> Enum.take(4)
["1", "2", "3", "4"]
iex> String.splitter("abcd", "") |> Enum.take(10)
["", "a", "b", "c", "d", ""]
iex> String.splitter("abcd", "", trim: true) |> Enum.take(10)
["a", "b", "c", "d"]A compiled pattern can also be given:
iex> pattern = :binary.compile_pattern([" ", ","])
iex> String.splitter("1,2 3,4 5,6 7,8,...,99999", pattern) |> Enum.take(4)
["1", "2", "3", "4"]Returns true if string starts with any of the prefixes given.
prefix can be either a string, a list of strings, or a compiled
pattern.
Examples
iex> String.starts_with?("elixir", "eli")
true
iex> String.starts_with?("elixir", ["erlang", "elixir"])
true
iex> String.starts_with?("elixir", ["erlang", "ruby"])
falseA compiled pattern can also be given:
iex> pattern = :binary.compile_pattern(["erlang", "elixir"])
iex> String.starts_with?("elixir", pattern)
trueAn empty string will always match:
iex> String.starts_with?("elixir", "")
true
iex> String.starts_with?("elixir", ["", "other"])
trueConverts a string to an atom.
Warning: this function creates atoms dynamically and atoms are
not garbage-collected. Therefore, string should not be an
untrusted value, such as input received from a socket or during
a web request. Consider using to_existing_atom/1 instead.
By default, the maximum number of atoms is 1_048_576. This limit
can be raised or lowered using the VM option +t.
The maximum atom size is of 255 Unicode code points.
Inlined by the compiler.
Examples
iex> String.to_atom("my_atom")
:my_atomConverts a string into a charlist.
Specifically, this function takes a UTF-8 encoded binary and returns a list of its integer
code points. It is similar to codepoints/1 except that the latter returns a list of code points as
strings.
In case you need to work with bytes, take a look at the
:binary module.
Examples
iex> String.to_charlist("æß")
'æß'Converts a string to an existing atom.
The maximum atom size is of 255 Unicode code points.
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 errorReturns a float whose text representation is string.
string must be the string representation of a float including a decimal point.
In order to parse a string without decimal point as a float then Float.parse/1
should be used. Otherwise, an ArgumentError will be raised.
Inlined by the compiler.
Examples
iex> String.to_float("2.2017764e+0")
2.2017764
iex> String.to_float("3.0")
3.0
String.to_float("3")
** (ArgumentError) argument errorReturns an integer whose text representation is string.
string must be the string representation of an integer.
Otherwise, an ArgumentError will be raised. If you want
to parse a string that may contain an ill-formatted integer,
use Integer.parse/1.
Inlined by the compiler.
Examples
iex> String.to_integer("123")
123Passing a string that does not represent an integer leads to an error:
String.to_integer("invalid data")
** (ArgumentError) argument errorReturns an integer whose text representation is string in base base.
Inlined by the compiler.
Examples
iex> String.to_integer("3FF", 16)
1023Returns a string where all leading and trailing Unicode whitespaces have been removed.
Examples
iex> String.trim("\n abc\n ")
"abc"Returns a string where all leading and trailing to_trim characters have been
removed.
Examples
iex> String.trim("a abc a", "a")
" abc "Returns a string where all leading Unicode whitespaces have been removed.
Examples
iex> String.trim_leading("\n abc ")
"abc "Returns a string where all leading to_trim characters have been removed.
Examples
iex> String.trim_leading("__ abc _", "_")
" abc _"
iex> String.trim_leading("1 abc", "11")
"1 abc"Returns a string where all trailing Unicode whitespaces has been removed.
Examples
iex> String.trim_trailing(" abc\n ")
" abc"Returns a string where all trailing to_trim characters have been removed.
Examples
iex> String.trim_trailing("_ abc __", "_")
"_ abc "
iex> String.trim_trailing("abc 1", "11")
"abc 1"Converts all characters in the given string to uppercase according to mode.
mode may be :default, :ascii or :greek. The :default mode considers
all non-conditional transformations outlined in the Unicode standard. :ascii
uppercases only the letters a to z. :greek includes the context sensitive
mappings found in Greek.
Examples
iex> String.upcase("abcd")
"ABCD"
iex> String.upcase("ab 123 xpto")
"AB 123 XPTO"
iex> String.upcase("olá")
"OLÁ"The :ascii mode ignores Unicode characters and provides a more
performant implementation when you know the string contains only
ASCII characters:
iex> String.upcase("olá", :ascii)
"OLá"Checks whether string contains only valid characters.
Examples
iex> String.valid?("a")
true
iex> String.valid?("ø")
true
iex> String.valid?(<<0xFFFF::16>>)
false
iex> String.valid?(<<0xEF, 0xB7, 0x90>>)
true
iex> String.valid?("asd" <> <<0xFFFF::16>>)
false