# Strings

`Core.AbstractChar` — Type

The `AbstractChar` type is the supertype of all character implementations in Julia. A character represents a Unicode code point, and can be converted to an integer via the `codepoint` function in order to obtain the numerical value of the code point, or constructed from the same integer. These numerical values determine how characters are compared with `<` and `==`, for example. New `T <: AbstractChar` types should define a `codepoint(::T)` method and a `T(::UInt32)` constructor, at minimum.

A given `AbstractChar` subtype may be capable of representing only a subset of Unicode, in which case conversion from an unsupported `UInt32` value may throw an error. Conversely, the built-in `Char` type represents a superset of Unicode (in order to losslessly encode invalid byte streams), in which case conversion of a non-Unicode value to `UInt32` throws an error. The `isvalid` function can be used to check which codepoints are representable in a given `AbstractChar` type.

Internally, an `AbstractChar` type may use a variety of encodings. Conversion via `codepoint(char)` will not reveal this encoding because it always returns the Unicode value of the character. `print(io, c)` of any `c::AbstractChar` produces an encoding determined by `io` (UTF-8 for all built-in `IO` types), via conversion to `Char` if necessary.

`write(io, c)`, in contrast, may emit an encoding depending on `typeof(c)`, and `read(io, typeof(c))` should read the same encoding as `write`. New `AbstractChar` types must provide their own implementations of `write` and `read`.

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`Core.Char` — Type

    Char(c::Union{Number,AbstractChar})

`Char` is a 32-bit `AbstractChar` type that is the default representation of characters in Julia. `Char` is the type used for character literals like `'x'` and it is also the element type of `String`.

In order to losslessly represent arbitrary byte streams stored in a `String`, a `Char` value may store information that cannot be converted to a Unicode codepoint — converting such a `Char` to `UInt32` will throw an error. The `isvalid(c::Char)` function can be used to query whether `c` represents a valid Unicode character.

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`Base.codepoint` — Function

    codepoint(c::AbstractChar) -> Integer

Return the Unicode codepoint (an unsigned integer) corresponding to the character `c` (or throw an exception if `c` does not represent a valid character). For `Char`, this is a `UInt32` value, but `AbstractChar` types that represent only a subset of Unicode may return a different-sized integer (e.g. `UInt8`).

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`Base.length` — Method

    length(s::AbstractString) -> Int
    length(s::AbstractString, i::Integer, j::Integer) -> Int

Return the number of characters in string `s` from indices `i` through `j`.

This is computed as the number of code unit indices from `i` to `j` which are valid character indices. With only a single string argument, this computes the number of characters in the entire string. With `i` and `j` arguments it computes the number of indices between `i` and `j` inclusive that are valid indices in the string `s`. In addition to in-bounds values, `i` may take the out-of-bounds value `ncodeunits(s) + 1` and `j` may take the out-of-bounds value `0`.

Note

The time complexity of this operation is linear in general. That is, it will take the time proportional to the number of bytes or characters in the string because it counts the value on the fly. This is in contrast to the method for arrays, which is a constant-time operation.

See also `isvalid`, `ncodeunits`, `lastindex`, `thisind`, `nextind`, `prevind`.

Examples

    julia> length("jμΛIα")
    5

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`Base.sizeof` — Method

    sizeof(str::AbstractString)

Size, in bytes, of the string `str`. Equal to the number of code units in `str` multiplied by the size, in bytes, of one code unit in `str`.

Examples

    julia> sizeof("")
    0

    julia> sizeof("∀")
    3

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`Base.:*` — Method

    *(s::Union{AbstractString, AbstractChar}, t::Union{AbstractString, AbstractChar}...) -> AbstractString

Concatenate strings and/or characters, producing a `String`. This is equivalent to calling the `string` function on the arguments. Concatenation of built-in string types always produces a value of type `String` but other string types may choose to return a string of a different type as appropriate.

Examples

    julia> "Hello " * "world"
    "Hello world"

    julia> 'j' * "ulia"
    "julia"

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`Base.:^` — Method

    ^(s::Union{AbstractString,AbstractChar}, n::Integer)

Repeat a string or character `n` times. This can also be written as `repeat(s, n)`.

See also `repeat`.

Examples

    julia> "Test "^3
    "Test Test Test "

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`Base.string` — Function

    string(n::Integer; base::Integer = 10, pad::Integer = 1)

Convert an integer `n` to a string in the given `base`, optionally specifying a number of digits to pad to.

See also `digits`, `bitstring`, `count_zeros`.

Examples

    julia> string(5, base = 13, pad = 4)
    "0005"

    julia> string(-13, base = 5, pad = 4)
    "-0023"

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    string(xs...)

Create a string from any values using the `print` function.

`string` should usually not be defined directly. Instead, define a method `print(io::IO, x::MyType)`. If `string(x)` for a certain type needs to be highly efficient, then it may make sense to add a method to `string` and define `print(io::IO, x::MyType) = print(io, string(x))` to ensure the functions are consistent.

See also: `String`, `repr`, `sprint`, `show`.

Examples

    julia> string("a", 1, true)
    "a1true"

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`Base.repeat` — Method

    repeat(s::AbstractString, r::Integer)

Repeat a string `r` times. This can be written as `s^r`.

See also `^`.

Examples

    julia> repeat("ha", 3)
    "hahaha"

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`Base.repeat` — Method

    repeat(c::AbstractChar, r::Integer) -> String

Repeat a character `r` times. This can equivalently be accomplished by calling `c^r`.

Examples

    julia> repeat('A', 3)
    "AAA"

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`Base.repr` — Method

    repr(x; context=nothing)

Create a string from any value using the `show` function. You should not add methods to `repr`; define a `show` method instead.

The optional keyword argument `context` can be set to a `:key=>value` pair, a tuple of `:key=>value` pairs, or an `IO` or `IOContext` object whose attributes are used for the I/O stream passed to `show`.

Note that `repr(x)` is usually similar to how the value of `x` would be entered in Julia. See also `repr(MIME("text/plain"), x)` to instead return a "pretty-printed" version of `x` designed more for human consumption, equivalent to the REPL display of `x`.

Julia 1.7

Passing a tuple to keyword `context` requires Julia 1.7 or later.

Examples

    julia> repr(1)
    "1"

    julia> repr(zeros(3))
    "[0.0, 0.0, 0.0]"

    julia> repr(big(1/3))
    "0.333333333333333314829616256247390992939472198486328125"

    julia> repr(big(1/3), context=:compact => true)
    "0.333333"

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`Core.String` — Method

    String(s::AbstractString)

Convert a string to a contiguous byte array representation encoded as UTF-8 bytes. This representation is often appropriate for passing strings to C.

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`Base.SubString` — Type

    SubString(s::AbstractString, i::Integer, j::Integer=lastindex(s))
    SubString(s::AbstractString, r::UnitRange{<:Integer})

Like `getindex`, but returns a view into the parent string `s` within range `i:j` or `r` respectively instead of making a copy.

Examples

    julia> SubString("abc", 1, 2)
    "ab"

    julia> SubString("abc", 1:2)
    "ab"

    julia> SubString("abc", 2)
    "bc"

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`Base.transcode` — Function

    transcode(T, src)

Convert string data between Unicode encodings. `src` is either a `String` or a `Vector{UIntXX}` of UTF-XX code units, where `XX` is 8, 16, or 32. `T` indicates the encoding of the return value: `String` to return a (UTF-8 encoded) `String` or `UIntXX` to return a `Vector{UIntXX}` of UTF-`XX` data. (The alias `Cwchar_t` can also be used as the integer type, for converting `wchar_t*` strings used by external C libraries.)

The `transcode` function succeeds as long as the input data can be reasonably represented in the target encoding; it always succeeds for conversions between UTF-XX encodings, even for invalid Unicode data.

Only conversion to/from UTF-8 is currently supported.

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`Base.unsafe_string` — Function

    unsafe_string(p::Ptr{UInt8}, [length::Integer])

Copy a string from the address of a C-style (NUL-terminated) string encoded as UTF-8. (The pointer can be safely freed afterwards.) If `length` is specified (the length of the data in bytes), the string does not have to be NUL-terminated.

This function is labeled "unsafe" because it will crash if `p` is not a valid memory address to data of the requested length.

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`Base.ncodeunits` — Method

    ncodeunits(s::AbstractString) -> Int

Return the number of code units in a string. Indices that are in bounds to access this string must satisfy `1 ≤ i ≤ ncodeunits(s)`. Not all such indices are valid – they may not be the start of a character, but they will return a code unit value when calling `codeunit(s,i)`.

Examples

    julia> ncodeunits("The Julia Language")
    18

    julia> ncodeunits("∫eˣ")
    6

    julia> ncodeunits('∫'), ncodeunits('e'), ncodeunits('ˣ')
    (3, 1, 2)

See also `codeunit`, `checkbounds`, `sizeof`, `length`, `lastindex`.

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`Base.codeunit` — Function

    codeunit(s::AbstractString) -> Type{<:Union{UInt8, UInt16, UInt32}}

Return the code unit type of the given string object. For ASCII, Latin-1, or UTF-8 encoded strings, this would be `UInt8`; for UCS-2 and UTF-16 it would be `UInt16`; for UTF-32 it would be `UInt32`. The code unit type need not be limited to these three types, but it's hard to think of widely used string encodings that don't use one of these units. `codeunit(s)` is the same as `typeof(codeunit(s,1))` when `s` is a non-empty string.

See also `ncodeunits`.

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    codeunit(s::AbstractString, i::Integer) -> Union{UInt8, UInt16, UInt32}

Return the code unit value in the string `s` at index `i`. Note that

    codeunit(s, i) :: codeunit(s)

I.e. the value returned by `codeunit(s, i)` is of the type returned by `codeunit(s)`.

Examples

    julia> a = codeunit("Hello", 2)
    0x65

    julia> typeof(a)
    UInt8

See also `ncodeunits`, `checkbounds`.

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`Base.codeunits` — Function

    codeunits(s::AbstractString)

Obtain a vector-like object containing the code units of a string. Returns a `CodeUnits` wrapper by default, but `codeunits` may optionally be defined for new string types if necessary.

Examples

    julia> codeunits("Juλia")
    6-element Base.CodeUnits{UInt8, String}:
     0x4a
     0x75
     0xce
     0xbb
     0x69
     0x61

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`Base.ascii` — Function

    ascii(s::AbstractString)

Convert a string to `String` type and check that it contains only ASCII data, otherwise throwing an `ArgumentError` indicating the position of the first non-ASCII byte.

Examples

    julia> ascii("abcdeγfgh")
    ERROR: ArgumentError: invalid ASCII at index 6 in "abcdeγfgh"
    Stacktrace:
    [...]

    julia> ascii("abcdefgh")
    "abcdefgh"

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`Base.Regex` — Type

    Regex(pattern[, flags])

A type representing a regular expression. `Regex` objects can be used to match strings with `match`.

`Regex` objects can be created using the `@r_str` string macro. The `Regex(pattern[, flags])` constructor is usually used if the `pattern` string needs to be interpolated. See the documentation of the string macro for details on flags.

Note

To escape interpolated variables use `\Q` and `\E` (e.g. `Regex("\\Q$x\\E")`)

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`Base.@r_str` — Macro

    @r_str -> Regex

Construct a regex, such as `r"^[a-z]*$"`, without interpolation and unescaping (except for quotation mark `"` which still has to be escaped). The regex also accepts one or more flags, listed after the ending quote, to change its behaviour:

- `i` enables case-insensitive matching
- `m` treats the `^` and `$` tokens as matching the start and end of individual lines, as opposed to the whole string.
- `s` allows the `.` modifier to match newlines.
- `x` enables "comment mode": whitespace is enabled except when escaped with `\`, and `#` is treated as starting a comment.
- `a` disables `UCP` mode (enables ASCII mode). By default `\B`, `\b`, `\D`, `\d`, `\S`, `\s`, `\W`, `\w`, etc. match based on Unicode character properties. With this option, these sequences only match ASCII characters.

See `Regex` if interpolation is needed.

Examples

    julia> match(r"a+.*b+.*?d$"ism, "Goodbye,\nOh, angry,\nBad world\n")
    RegexMatch("angry,\nBad world")

This regex has the first three flags enabled.

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`Base.SubstitutionString` — Type

    SubstitutionString(substr)

Stores the given string `substr` as a `SubstitutionString`, for use in regular expression substitutions. Most commonly constructed using the `@s_str` macro.

    julia> SubstitutionString("Hello \\g<name>, it's \\1")
    s"Hello \g<name>, it's \1"

    julia> subst = s"Hello \g<name>, it's \1"
    s"Hello \g<name>, it's \1"

    julia> typeof(subst)
    SubstitutionString{String}

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`Base.@s_str` — Macro

    @s_str -> SubstitutionString

Construct a substitution string, used for regular expression substitutions. Within the string, sequences of the form `\N` refer to the Nth capture group in the regex, and `\g<groupname>` refers to a named capture group with name `groupname`.

    julia> msg = "#Hello# from Julia";

    julia> replace(msg, r"#(.+)# from (?<from>\w+)" => s"FROM: \g<from>; MESSAGE: \1")
    "FROM: Julia; MESSAGE: Hello"

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`Base.@raw_str` — Macro

    @raw_str -> String

Create a raw string without interpolation and unescaping. The exception is that quotation marks still must be escaped. Backslashes escape both quotation marks and other backslashes, but only when a sequence of backslashes precedes a quote character. Thus, 2n backslashes followed by a quote encodes n backslashes and the end of the literal while 2n+1 backslashes followed by a quote encodes n backslashes followed by a quote character.

Examples

    julia> println(raw"\ $x")
    \ $x

    julia> println(raw"\"")
    "

    julia> println(raw"\\\"")
    \"

    julia> println(raw"\\x \\\"")
    \\x \"

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`Base.@b_str` — Macro

    @b_str

Create an immutable byte (`UInt8`) vector using string syntax.

Examples

    julia> v = b"12\x01\x02"
    4-element Base.CodeUnits{UInt8, String}:
     0x31
     0x32
     0x01
     0x02

    julia> v[2]
    0x32

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`Base.Docs.@html_str` — Macro

    @html_str -> Docs.HTML

Create an `HTML` object from a literal string.

Examples

    julia> html"Julia"
    HTML{String}("Julia")

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`Base.Docs.@text_str` — Macro

    @text_str -> Docs.Text

Create a `Text` object from a literal string.

Examples

    julia> text"Julia"
    Julia

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`Base.isvalid` — Method

    isvalid(value) -> Bool

Returns `true` if the given value is valid for its type, which currently can be either `AbstractChar` or `String` or `SubString{String}`.

Examples

    julia> isvalid(Char(0xd800))
    false

    julia> isvalid(SubString(String(UInt8[0xfe,0x80,0x80,0x80,0x80,0x80]),1,2))
    false

    julia> isvalid(Char(0xd799))
    true

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`Base.isvalid` — Method

    isvalid(T, value) -> Bool

Returns `true` if the given value is valid for that type. Types currently can be either `AbstractChar` or `String`. Values for `AbstractChar` can be of type `AbstractChar` or `UInt32`. Values for `String` can be of that type, `SubString{String}`, `Vector{UInt8}`, or a contiguous subarray thereof.

Examples

    julia> isvalid(Char, 0xd800)
    false

    julia> isvalid(String, SubString("thisisvalid",1,5))
    true

    julia> isvalid(Char, 0xd799)
    true

Julia 1.6

Support for subarray values was added in Julia 1.6.

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`Base.isvalid` — Method

    isvalid(s::AbstractString, i::Integer) -> Bool

Predicate indicating whether the given index is the start of the encoding of a character in `s` or not. If `isvalid(s, i)` is true then `s[i]` will return the character whose encoding starts at that index, if it's false, then `s[i]` will raise an invalid index error or a bounds error depending on if `i` is in bounds. In order for `isvalid(s, i)` to be an O(1) function, the encoding of `s` must be self-synchronizing. This is a basic assumption of Julia's generic string support.

See also `getindex`, `iterate`, `thisind`, `nextind`, `prevind`, `length`.

Examples

    julia> str = "αβγdef";

    julia> isvalid(str, 1)
    true

    julia> str[1]
    'α': Unicode U+03B1 (category Ll: Letter, lowercase)

    julia> isvalid(str, 2)
    false

    julia> str[2]
    ERROR: StringIndexError: invalid index [2], valid nearby indices [1]=>'α', [3]=>'β'
    Stacktrace:
    [...]

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`Base.match` — Function

    match(r::Regex, s::AbstractString[, idx::Integer[, addopts]])

Search for the first match of the regular expression `r` in `s` and return a `RegexMatch` object containing the match, or nothing if the match failed. The matching substring can be retrieved by accessing `m.match` and the captured sequences can be retrieved by accessing `m.captures` The optional `idx` argument specifies an index at which to start the search.

Examples

    julia> rx = r"a(.)a"
    r"a(.)a"

    julia> m = match(rx, "cabac")
    RegexMatch("aba", 1="b")

    julia> m.captures
    1-element Vector{Union{Nothing, SubString{String}}}:
     "b"

    julia> m.match
    "aba"

    julia> match(rx, "cabac", 3) === nothing
    true

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`Base.eachmatch` — Function

    eachmatch(r::Regex, s::AbstractString; overlap::Bool=false)

Search for all matches of the regular expression `r` in `s` and return an iterator over the matches. If `overlap` is `true`, the matching sequences are allowed to overlap indices in the original string, otherwise they must be from distinct character ranges.

Examples

    julia> rx = r"a.a"
    r"a.a"

    julia> m = eachmatch(rx, "a1a2a3a")
    Base.RegexMatchIterator(r"a.a", "a1a2a3a", false)

    julia> collect(m)
    2-element Vector{RegexMatch}:
     RegexMatch("a1a")
     RegexMatch("a3a")

    julia> collect(eachmatch(rx, "a1a2a3a", overlap = true))
    3-element Vector{RegexMatch}:
     RegexMatch("a1a")
     RegexMatch("a2a")
     RegexMatch("a3a")

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`Base.RegexMatch` — Type

    RegexMatch

A type representing a single match to a `Regex` found in a string. Typically created from the `match` function.

The `match` field stores the substring of the entire matched string. The `captures` field stores the substrings for each capture group, indexed by number. To index by capture group name, the entire match object should be indexed instead, as shown in the examples. The location of the start of the match is stored in the `offset` field. The `offsets` field stores the locations of the start of each capture group, with 0 denoting a group that was not captured.

This type can be used as an iterator over the capture groups of the `Regex`, yielding the substrings captured in each group. Because of this, the captures of a match can be destructured. If a group was not captured, `nothing` will be yielded instead of a substring.

Methods that accept a `RegexMatch` object are defined for `iterate`, `length`, `eltype`, `keys`, `haskey`, and `getindex`, where keys are the the names or numbers of a capture group. See `keys` for more information.

Examples

    julia> m = match(r"(?<hour>\d+):(?<minute>\d+)(am|pm)?", "11:30 in the morning")
    RegexMatch("11:30", hour="11", minute="30", 3=nothing)

    julia> hr, min, ampm = m;

    julia> hr
    "11"

    julia> m["minute"]
    "30"

    julia> m.match
    "11:30"

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`Base.keys` — Method

    keys(m::RegexMatch) -> Vector

Return a vector of keys for all capture groups of the underlying regex. A key is included even if the capture group fails to match. That is, `idx` will be in the return value even if `m[idx] == nothing`.

Unnamed capture groups will have integer keys corresponding to their index. Named capture groups will have string keys.

Julia 1.6

This method was added in Julia 1.6

Examples

    julia> keys(match(r"(?<hour>\d+):(?<minute>\d+)(am|pm)?", "11:30"))
    3-element Vector{Any}:
      "hour"
      "minute"
     3

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`Base.isless` — Method

    isless(a::AbstractString, b::AbstractString) -> Bool

Test whether string `a` comes before string `b` in alphabetical order (technically, in lexicographical order by Unicode code points).

Examples

    julia> isless("a", "b")
    true

    julia> isless("β", "α")
    false

    julia> isless("a", "a")
    false

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`Base.:==` — Method

    ==(a::AbstractString, b::AbstractString) -> Bool

Test whether two strings are equal character by character (technically, Unicode code point by code point).

Examples

    julia> "abc" == "abc"
    true

    julia> "abc" == "αβγ"
    false

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`Base.cmp` — Method

    cmp(a::AbstractString, b::AbstractString) -> Int

Compare two strings. Return `0` if both strings have the same length and the character at each index is the same in both strings. Return `-1` if `a` is a prefix of `b`, or if `a` comes before `b` in alphabetical order. Return `1` if `b` is a prefix of `a`, or if `b` comes before `a` in alphabetical order (technically, lexicographical order by Unicode code points).

Examples

    julia> cmp("abc", "abc")
    0

    julia> cmp("ab", "abc")
    -1

    julia> cmp("abc", "ab")
    1

    julia> cmp("ab", "ac")
    -1

    julia> cmp("ac", "ab")
    1

    julia> cmp("α", "a")
    1

    julia> cmp("b", "β")
    -1

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`Base.lpad` — Function

    lpad(s, n::Integer, p::Union{AbstractChar,AbstractString}=' ') -> String

Stringify `s` and pad the resulting string on the left with `p` to make it `n` characters (in `textwidth`) long. If `s` is already `n` characters long, an equal string is returned. Pad with spaces by default.

Examples

    julia> lpad("March", 10)
    "     March"

Julia 1.7

In Julia 1.7, this function was changed to use `textwidth` rather than a raw character (codepoint) count.

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`Base.rpad` — Function

    rpad(s, n::Integer, p::Union{AbstractChar,AbstractString}=' ') -> String

Stringify `s` and pad the resulting string on the right with `p` to make it `n` characters (in `textwidth`) long. If `s` is already `n` characters long, an equal string is returned. Pad with spaces by default.

Examples

    julia> rpad("March", 20)
    "March               "

Julia 1.7

In Julia 1.7, this function was changed to use `textwidth` rather than a raw character (codepoint) count.

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`Base.findfirst` — Method

    findfirst(pattern::AbstractString, string::AbstractString)
    findfirst(pattern::AbstractPattern, string::String)

Find the first occurrence of `pattern` in `string`. Equivalent to `findnext(pattern, string, firstindex(s))`.

Examples

    julia> findfirst("z", "Hello to the world") # returns nothing, but not printed in the REPL

    julia> findfirst("Julia", "JuliaLang")
    1:5

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`Base.findnext` — Method

    findnext(pattern::AbstractString, string::AbstractString, start::Integer)
    findnext(pattern::AbstractPattern, string::String, start::Integer)

Find the next occurrence of `pattern` in `string` starting at position `start`. `pattern` can be either a string, or a regular expression, in which case `string` must be of type `String`.

The return value is a range of indices where the matching sequence is found, such that `s[findnext(x, s, i)] == x`:

`findnext("substring", string, i)` == `start:stop` such that `string[start:stop] == "substring"` and `i <= start`, or `nothing` if unmatched.

Examples

    julia> findnext("z", "Hello to the world", 1) === nothing
    true

    julia> findnext("o", "Hello to the world", 6)
    8:8

    julia> findnext("Lang", "JuliaLang", 2)
    6:9

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`Base.findnext` — Method

    findnext(ch::AbstractChar, string::AbstractString, start::Integer)

Find the next occurrence of character `ch` in `string` starting at position `start`.

Julia 1.3

This method requires at least Julia 1.3.

Examples

    julia> findnext('z', "Hello to the world", 1) === nothing
    true

    julia> findnext('o', "Hello to the world", 6)
    8

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`Base.findlast` — Method

    findlast(pattern::AbstractString, string::AbstractString)

Find the last occurrence of `pattern` in `string`. Equivalent to `findprev(pattern, string, lastindex(string))`.

Examples

    julia> findlast("o", "Hello to the world")
    15:15

    julia> findfirst("Julia", "JuliaLang")
    1:5

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`Base.findlast` — Method

    findlast(ch::AbstractChar, string::AbstractString)

Find the last occurrence of character `ch` in `string`.

Julia 1.3

This method requires at least Julia 1.3.

Examples

    julia> findlast('p', "happy")
    4

    julia> findlast('z', "happy") === nothing
    true

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`Base.findprev` — Method

    findprev(pattern::AbstractString, string::AbstractString, start::Integer)

Find the previous occurrence of `pattern` in `string` starting at position `start`.

The return value is a range of indices where the matching sequence is found, such that `s[findprev(x, s, i)] == x`:

`findprev("substring", string, i)` == `start:stop` such that `string[start:stop] == "substring"` and `stop <= i`, or `nothing` if unmatched.

Examples

    julia> findprev("z", "Hello to the world", 18) === nothing
    true

    julia> findprev("o", "Hello to the world", 18)
    15:15

    julia> findprev("Julia", "JuliaLang", 6)
    1:5

source
`Base.occursin` — Function

    occursin(needle::Union{AbstractString,AbstractPattern,AbstractChar}, haystack::AbstractString)

Determine whether the first argument is a substring of the second. If `needle` is a regular expression, checks whether `haystack` contains a match.

Examples

    julia> occursin("Julia", "JuliaLang is pretty cool!")
    true

    julia> occursin('a', "JuliaLang is pretty cool!")
    true

    julia> occursin(r"a.a", "aba")
    true

    julia> occursin(r"a.a", "abba")
    false

See also `contains`.

source

    occursin(haystack)

Create a function that checks whether its argument occurs in `haystack`, i.e. a function equivalent to `needle -> occursin(needle, haystack)`.

The returned function is of type `Base.Fix2{typeof(occursin)}`.

Julia 1.6

This method requires Julia 1.6 or later.

source
`Base.reverse` — Method

    reverse(s::AbstractString) -> AbstractString

Reverses a string. Technically, this function reverses the codepoints in a string and its main utility is for reversed-order string processing, especially for reversed regular-expression searches. See also `reverseind` to convert indices in `s` to indices in `reverse(s)` and vice-versa, and `graphemes` from module `Unicode` to operate on user-visible "characters" (graphemes) rather than codepoints. See also `Iterators.reverse` for reverse-order iteration without making a copy. Custom string types must implement the `reverse` function themselves and should typically return a string with the same type and encoding. If they return a string with a different encoding, they must also override `reverseind` for that string type to satisfy `s[reverseind(s,i)] == reverse(s)[i]`.

Examples

    julia> reverse("JuliaLang")
    "gnaLailuJ"

Note

The examples below may be rendered differently on different systems. The comments indicate how they're supposed to be rendered

Combining characters can lead to surprising results:

    julia> reverse("ax̂e") # hat is above x in the input, above e in the output
    "êxa"

    julia> using Unicode

    julia> join(reverse(collect(graphemes("ax̂e")))) # reverses graphemes; hat is above x in both in- and output
    "ex̂a"

source
`Base.replace` — Method

    replace(s::AbstractString, pat=>r, [pat2=>r2, ...]; [count::Integer])

Search for the given pattern `pat` in `s`, and replace each occurrence with `r`. If `count` is provided, replace at most `count` occurrences. `pat` may be a single character, a vector or a set of characters, a string, or a regular expression. If `r` is a function, each occurrence is replaced with `r(s)` where `s` is the matched substring (when `pat` is a `AbstractPattern` or `AbstractString`) or character (when `pat` is an `AbstractChar` or a collection of `AbstractChar`). If `pat` is a regular expression and `r` is a `SubstitutionString`, then capture group references in `r` are replaced with the corresponding matched text. To remove instances of `pat` from `string`, set `r` to the empty `String` (`""`).

Multiple patterns can be specified, and they will be applied left-to-right simultaneously, so only one pattern will be applied to any character, and the patterns will only be applied to the input text, not the replacements.

Julia 1.7

Support for multiple patterns requires version 1.7.

Examples

    julia> replace("Python is a programming language.", "Python" => "Julia")
    "Julia is a programming language."

    julia> replace("The quick foxes run quickly.", "quick" => "slow", count=1)
    "The slow foxes run quickly."

    julia> replace("The quick foxes run quickly.", "quick" => "", count=1)
    "The  foxes run quickly."

    julia> replace("The quick foxes run quickly.", r"fox(es)?" => s"bus\1")
    "The quick buses run quickly."

    julia> replace("abcabc", "a" => "b", "b" => "c", r".+" => "a")
    "bca"

source
`Base.split` — Function

    split(str::AbstractString, dlm; limit::Integer=0, keepempty::Bool=true)
    split(str::AbstractString; limit::Integer=0, keepempty::Bool=false)

Split `str` into an array of substrings on occurrences of the delimiter(s) `dlm`. `dlm` can be any of the formats allowed by `findnext`'s first argument (i.e. as a string, regular expression or a function), or as a single character or collection of characters.

If `dlm` is omitted, it defaults to `isspace`.

The optional keyword arguments are:

- `limit`: the maximum size of the result. `limit=0` implies no maximum (default)
- `keepempty`: whether empty fields should be kept in the result. Default is `false` without a `dlm` argument, `true` with a `dlm` argument.

See also `rsplit`.

Examples

    julia> a = "Ma.rch"
    "Ma.rch"

    julia> split(a, ".")
    2-element Vector{SubString{String}}:
     "Ma"
     "rch"

source
`Base.rsplit` — Function

    rsplit(s::AbstractString; limit::Integer=0, keepempty::Bool=false)
    rsplit(s::AbstractString, chars; limit::Integer=0, keepempty::Bool=true)

Similar to `split`, but starting from the end of the string.

Examples

    julia> a = "M.a.r.c.h"
    "M.a.r.c.h"

    julia> rsplit(a, ".")
    5-element Vector{SubString{String}}:
     "M"
     "a"
     "r"
     "c"
     "h"

    julia> rsplit(a, "."; limit=1)
    1-element Vector{SubString{String}}:
     "M.a.r.c.h"

    julia> rsplit(a, "."; limit=2)
    2-element Vector{SubString{String}}:
     "M.a.r.c"
     "h"

source
`Base.strip` — Function

    strip([pred=isspace,] str::AbstractString) -> SubString
    strip(str::AbstractString, chars) -> SubString

Remove leading and trailing characters from `str`, either those specified by `chars` or those for which the function `pred` returns `true`.

The default behaviour is to remove leading and trailing whitespace and delimiters: see `isspace` for precise details.

The optional `chars` argument specifies which characters to remove: it can be a single character, vector or set of characters.

See also `lstrip` and `rstrip`.

Julia 1.2

The method which accepts a predicate function requires Julia 1.2 or later.

Examples

    julia> strip("{3, 5}\n", ['{', '}', '\n'])
    "3, 5"

source
`Base.lstrip` — Function

    lstrip([pred=isspace,] str::AbstractString) -> SubString
    lstrip(str::AbstractString, chars) -> SubString

Remove leading characters from `str`, either those specified by `chars` or those for which the function `pred` returns `true`.

The default behaviour is to remove leading whitespace and delimiters: see `isspace` for precise details.

The optional `chars` argument specifies which characters to remove: it can be a single character, or a vector or set of characters.

See also `strip` and `rstrip`.

Examples

    julia> a = lpad("March", 20)
    "               March"

    julia> lstrip(a)
    "March"

source
`Base.rstrip` — Function

    rstrip([pred=isspace,] str::AbstractString) -> SubString
    rstrip(str::AbstractString, chars) -> SubString

Remove trailing characters from `str`, either those specified by `chars` or those for which the function `pred` returns `true`.

The default behaviour is to remove trailing whitespace and delimiters: see `isspace` for precise details.

The optional `chars` argument specifies which characters to remove: it can be a single character, or a vector or set of characters.

See also `strip` and `lstrip`.

Examples

    julia> a = rpad("March", 20)
    "March               "

    julia> rstrip(a)
    "March"

source
`Base.startswith` — Function

    startswith(s::AbstractString, prefix::AbstractString)

Return `true` if `s` starts with `prefix`. If `prefix` is a vector or set of characters, test whether the first character of `s` belongs to that set.

See also `endswith`, `contains`.

Examples

    julia> startswith("JuliaLang", "Julia")
    true

source

    startswith(prefix)

Create a function that checks whether its argument starts with `prefix`, i.e. a function equivalent to `y -> startswith(y, prefix)`.

The returned function is of type `Base.Fix2{typeof(startswith)}`, which can be used to implement specialized methods.

Julia 1.5

The single argument `startswith(prefix)` requires at least Julia 1.5.

Examples

    julia> startswith_julia = startswith("Julia");

    julia> startswith_julia("Julia")
    true

    julia> startswith_julia("NotJulia")
    false

source

    startswith(s::AbstractString, prefix::Regex)

Return `true` if `s` starts with the regex pattern, `prefix`.

Note

`startswith` does not compile the anchoring into the regular expression, but instead passes the anchoring as `match_option` to PCRE. If compile time is amortized, `occursin(r"^...", s)` is faster than `startswith(s, r"...")`.

See also `occursin` and `endswith`.

Julia 1.2

This method requires at least Julia 1.2.

Examples

    julia> startswith("JuliaLang", r"Julia|Romeo")
    true

source
`Base.endswith` — Function

    endswith(s::AbstractString, suffix::AbstractString)

Return `true` if `s` ends with `suffix`. If `suffix` is a vector or set of characters, test whether the last character of `s` belongs to that set.

See also `startswith`, `contains`.

Examples

    julia> endswith("Sunday", "day")
    true

source

    endswith(suffix)

Create a function that checks whether its argument ends with `suffix`, i.e. a function equivalent to `y -> endswith(y, suffix)`.

The returned function is of type `Base.Fix2{typeof(endswith)}`, which can be used to implement specialized methods.

Julia 1.5

The single argument `endswith(suffix)` requires at least Julia 1.5.

Examples

    julia> endswith_julia = endswith("Julia");

    julia> endswith_julia("Julia")
    true

    julia> endswith_julia("JuliaLang")
    false

source

    endswith(s::AbstractString, suffix::Regex)

Return `true` if `s` ends with the regex pattern, `suffix`.

Note

`endswith` does not compile the anchoring into the regular expression, but instead passes the anchoring as `match_option` to PCRE. If compile time is amortized, `occursin(r"...$", s)` is faster than `endswith(s, r"...")`.

See also `occursin` and `startswith`.

Julia 1.2

This method requires at least Julia 1.2.

Examples

    julia> endswith("JuliaLang", r"Lang|Roberts")
    true

source
`Base.contains` — Function

    contains(haystack::AbstractString, needle)

Return `true` if `haystack` contains `needle`. This is the same as `occursin(needle, haystack)`, but is provided for consistency with `startswith(haystack, needle)` and `endswith(haystack, needle)`.

See also `occursin`, `in`, `issubset`.

Examples

    julia> contains("JuliaLang is pretty cool!", "Julia")
    true

    julia> contains("JuliaLang is pretty cool!", 'a')
    true

    julia> contains("aba", r"a.a")
    true

    julia> contains("abba", r"a.a")
    false

Julia 1.5

The `contains` function requires at least Julia 1.5.

source

    contains(needle)

Create a function that checks whether its argument contains `needle`, i.e. a function equivalent to `haystack -> contains(haystack, needle)`.

The returned function is of type `Base.Fix2{typeof(contains)}`, which can be used to implement specialized methods.

source
`Base.first` — Method

    first(s::AbstractString, n::Integer)

Get a string consisting of the first `n` characters of `s`.

Examples

    julia> first("∀ϵ≠0: ϵ²>0", 0)
    ""

    julia> first("∀ϵ≠0: ϵ²>0", 1)
    "∀"

    julia> first("∀ϵ≠0: ϵ²>0", 3)
    "∀ϵ≠"

source
`Base.last` — Method

    last(s::AbstractString, n::Integer)

Get a string consisting of the last `n` characters of `s`.

Examples

    julia> last("∀ϵ≠0: ϵ²>0", 0)
    ""

    julia> last("∀ϵ≠0: ϵ²>0", 1)
    "0"

    julia> last("∀ϵ≠0: ϵ²>0", 3)
    "²>0"

source
`Base.Unicode.uppercase` — Function

    uppercase(s::AbstractString)

Return `s` with all characters converted to uppercase.

See also `lowercase`, `titlecase`, `uppercasefirst`.

Examples

    julia> uppercase("Julia")
    "JULIA"

source
`Base.Unicode.lowercase` — Function

    lowercase(s::AbstractString)

Return `s` with all characters converted to lowercase.

See also `uppercase`, `titlecase`, `lowercasefirst`.

Examples

    julia> lowercase("STRINGS AND THINGS")
    "strings and things"

source
`Base.Unicode.titlecase` — Function

    titlecase(s::AbstractString; [wordsep::Function], strict::Bool=true) -> String

Capitalize the first character of each word in `s`; if `strict` is true, every other character is converted to lowercase, otherwise they are left unchanged. By default, all non-letters beginning a new grapheme are considered as word separators; a predicate can be passed as the `wordsep` keyword to determine which characters should be considered as word separators. See also `uppercasefirst` to capitalize only the first character in `s`.

See also `uppercase`, `lowercase`, `uppercasefirst`.

Examples

    julia> titlecase("the JULIA programming language")
    "The Julia Programming Language"

    julia> titlecase("ISS - international space station", strict=false)
    "ISS - International Space Station"

    julia> titlecase("a-a b-b", wordsep = c->c==' ')
    "A-a B-b"

source
`Base.Unicode.uppercasefirst` — Function

    uppercasefirst(s::AbstractString) -> String

Return `s` with the first character converted to uppercase (technically "title case" for Unicode). See also `titlecase` to capitalize the first character of every word in `s`.

See also `lowercasefirst`, `uppercase`, `lowercase`, `titlecase`.

Examples

    julia> uppercasefirst("python")
    "Python"

source
`Base.Unicode.lowercasefirst` — Function

    lowercasefirst(s::AbstractString)

Return `s` with the first character converted to lowercase.

See also `uppercasefirst`, `uppercase`, `lowercase`, `titlecase`.

Examples

    julia> lowercasefirst("Julia")
    "julia"

source
`Base.join` — Function

    join([io::IO,] iterator [, delim [, last]])

Join any `iterator` into a single string, inserting the given delimiter (if any) between adjacent items. If `last` is given, it will be used instead of `delim` between the last two items. Each item of `iterator` is converted to a string via `print(io::IOBuffer, x)`. If `io` is given, the result is written to `io` rather than returned as a `String`.

Examples

    julia> join(["apples", "bananas", "pineapples"], ", ", " and ")
    "apples, bananas and pineapples"

    julia> join([1,2,3,4,5])
    "12345"

source
`Base.chop` — Function

    chop(s::AbstractString; head::Integer = 0, tail::Integer = 1)

Remove the first `head` and the last `tail` characters from `s`. The call `chop(s)` removes the last character from `s`. If it is requested to remove more characters than `length(s)` then an empty string is returned.

See also `chomp`, `startswith`, `first`.

Examples

    julia> a = "March"
    "March"

    julia> chop(a)
    "Marc"

    julia> chop(a, head = 1, tail = 2)
    "ar"

    julia> chop(a, head = 5, tail = 5)
    ""

source
`Base.chomp` — Function

    chomp(s::AbstractString) -> SubString

Remove a single trailing newline from a string.

See also `chop`.

Examples

    julia> chomp("Hello\n")
    "Hello"

source
`Base.thisind` — Function

    thisind(s::AbstractString, i::Integer) -> Int

If `i` is in bounds in `s` return the index of the start of the character whose encoding code unit `i` is part of. In other words, if `i` is the start of a character, return `i`; if `i` is not the start of a character, rewind until the start of a character and return that index. If `i` is equal to 0 or `ncodeunits(s)+1` return `i`. In all other cases throw `BoundsError`.

Examples

    julia> thisind("α", 0)
    0

    julia> thisind("α", 1)
    1

    julia> thisind("α", 2)
    1

    julia> thisind("α", 3)
    3

    julia> thisind("α", 4)
    ERROR: BoundsError: attempt to access 2-codeunit String at index [4]
    [...]

    julia> thisind("α", -1)
    ERROR: BoundsError: attempt to access 2-codeunit String at index [-1]
    [...]

source
`Base.nextind` — Function

    nextind(str::AbstractString, i::Integer, n::Integer=1) -> Int

- Case `n == 1`

  If `i` is in bounds in `s` return the index of the start of the character whose encoding starts after index `i`. In other words, if `i` is the start of a character, return the start of the next character; if `i` is not the start of a character, move forward until the start of a character and return that index. If `i` is equal to `0` return `1`. If `i` is in bounds but greater or equal to `lastindex(str)` return `ncodeunits(str)+1`. Otherwise throw `BoundsError`.

- Case `n > 1`

  Behaves like applying `n` times `nextind` for `n==1`. The only difference is that if `n` is so large that applying `nextind` would reach `ncodeunits(str)+1` then each remaining iteration increases the returned value by `1`. This means that in this case `nextind` can return a value greater than `ncodeunits(str)+1`.

- Case `n == 0`

  Return `i` only if `i` is a valid index in `s` or is equal to `0`. Otherwise `StringIndexError` or `BoundsError` is thrown.

Examples

    julia> nextind("α", 0)
    1

    julia> nextind("α", 1)
    3

    julia> nextind("α", 3)
    ERROR: BoundsError: attempt to access 2-codeunit String at index [3]
    [...]

    julia> nextind("α", 0, 2)
    3

    julia> nextind("α", 1, 2)
    4

source
`Base.prevind` — Function

    prevind(str::AbstractString, i::Integer, n::Integer=1) -> Int

- Case `n == 1`

  If `i` is in bounds in `s` return the index of the start of the character whose encoding starts before index `i`. In other words, if `i` is the start of a character, return the start of the previous character; if `i` is not the start of a character, rewind until the start of a character and return that index. If `i` is equal to `1` return `0`. If `i` is equal to `ncodeunits(str)+1` return `lastindex(str)`. Otherwise throw `BoundsError`.

- Case `n > 1`

  Behaves like applying `n` times `prevind` for `n==1`. The only difference is that if `n` is so large that applying `prevind` would reach `0` then each remaining iteration decreases the returned value by `1`. This means that in this case `prevind` can return a negative value.

- Case `n == 0`

  Return `i` only if `i` is a valid index in `str` or is equal to `ncodeunits(str)+1`. Otherwise `StringIndexError` or `BoundsError` is thrown.

Examples

    julia> prevind("α", 3)
    1

    julia> prevind("α", 1)
    0

    julia> prevind("α", 0)
    ERROR: BoundsError: attempt to access 2-codeunit String at index [0]
    [...]

    julia> prevind("α", 2, 2)
    0

    julia> prevind("α", 2, 3)
    -1

source
`Base.Unicode.textwidth` — Function

    textwidth(c)

Give the number of columns needed to print a character.

Examples

    julia> textwidth('α')
    1

    julia> textwidth('⛵')
    2

source

    textwidth(s::AbstractString)

Give the number of columns needed to print a string.

Examples

    julia> textwidth("March")
    5

source
`Base.isascii` — Function

    isascii(c::Union{AbstractChar,AbstractString}) -> Bool

Test whether a character belongs to the ASCII character set, or whether this is true for all elements of a string.

Examples

    julia> isascii('a')
    true

    julia> isascii('α')
    false

    julia> isascii("abc")
    true

    julia> isascii("αβγ")
    false

source
`Base.Unicode.iscntrl` — Function

    iscntrl(c::AbstractChar) -> Bool

Tests whether a character is a control character. Control characters are the non-printing characters of the Latin-1 subset of Unicode.

Examples

    julia> iscntrl('\x01')
    true

    julia> iscntrl('a')
    false

source
`Base.Unicode.isdigit` — Function

    isdigit(c::AbstractChar) -> Bool

Tests whether a character is a decimal digit (0-9).

Examples

    julia> isdigit('❤')
    false

    julia> isdigit('9')
    true

    julia> isdigit('α')
    false

source
`Base.Unicode.isletter` — Function

    isletter(c::AbstractChar) -> Bool

Test whether a character is a letter. A character is classified as a letter if it belongs to the Unicode general category Letter, i.e. a character whose category code begins with 'L'.

Examples

    julia> isletter('❤')
    false

    julia> isletter('α')
    true

    julia> isletter('9')
    false

source
`Base.Unicode.islowercase` — Function

    islowercase(c::AbstractChar) -> Bool

Tests whether a character is a lowercase letter (according to the Unicode standard's `Lowercase` derived property).

See also `isuppercase`.

Examples

    julia> islowercase('α')
    true

    julia> islowercase('Γ')
    false

    julia> islowercase('❤')
    false

source
`Base.Unicode.isnumeric` — Function

    isnumeric(c::AbstractChar) -> Bool

Tests whether a character is numeric. A character is classified as numeric if it belongs to the Unicode general category Number, i.e. a character whose category code begins with 'N'.

Note that this broad category includes characters such as ¾ and ௰. Use `isdigit` to check whether a character a decimal digit between 0 and 9.

Examples

    julia> isnumeric('௰')
    true

    julia> isnumeric('9')
    true

    julia> isnumeric('α')
    false

    julia> isnumeric('❤')
    false

source
`Base.Unicode.isprint` — Function

    isprint(c::AbstractChar) -> Bool

Tests whether a character is printable, including spaces, but not a control character.

Examples

    julia> isprint('\x01')
    false

    julia> isprint('A')
    true

source
`Base.Unicode.ispunct` — Function

    ispunct(c::AbstractChar) -> Bool

Tests whether a character belongs to the Unicode general category Punctuation, i.e. a character whose category code begins with 'P'.

Examples

    julia> ispunct('α')
    false

    julia> ispunct('/')
    true

    julia> ispunct(';')
    true

source
`Base.Unicode.isspace` — Function

    isspace(c::AbstractChar) -> Bool

Tests whether a character is any whitespace character. Includes ASCII characters '\t', '\n', '\v', '\f', '\r', and ' ', Latin-1 character U+0085, and characters in Unicode category Zs.

Examples

    julia> isspace('\n')
    true

    julia> isspace('\r')
    true

    julia> isspace(' ')
    true

    julia> isspace('\x20')
    true

source
`Base.Unicode.isuppercase` — Function

    isuppercase(c::AbstractChar) -> Bool

Tests whether a character is an uppercase letter (according to the Unicode standard's `Uppercase` derived property).

See also `islowercase`.

Examples

    julia> isuppercase('γ')
    false

    julia> isuppercase('Γ')
    true

    julia> isuppercase('❤')
    false

source
`Base.Unicode.isxdigit` — Function

    isxdigit(c::AbstractChar) -> Bool

Test whether a character is a valid hexadecimal digit. Note that this does not include `x` (as in the standard `0x` prefix).

Examples

    julia> isxdigit('a')
    true

    julia> isxdigit('x')
    false

source
`Base.escape_string` — Function

    escape_string(str::AbstractString[, esc]; keep = ())::AbstractString
    escape_string(io, str::AbstractString[, esc]; keep = ())::Nothing

General escaping of traditional C and Unicode escape sequences. The first form returns the escaped string, the second prints the result to `io`.

Backslashes (`\`) are escaped with a double-backslash (`"\\"`). Non-printable characters are escaped either with their standard C escape codes, `"\0"` for NUL (if unambiguous), unicode code point (`"\u"` prefix) or hex (`"\x"` prefix).

The optional `esc` argument specifies any additional characters that should also be escaped by a prepending backslash (`"` is also escaped by default in the first form).

The argument `keep` specifies a collection of characters which are to be kept as they are. Notice that `esc` has precedence here.

See also `unescape_string` for the reverse operation.

Julia 1.7

The `keep` argument is available as of Julia 1.7.

Examples

    julia> escape_string("aaa\nbbb")
    "aaa\\nbbb"

    julia> escape_string("aaa\nbbb"; keep = '\n')
    "aaa\nbbb"

    julia> escape_string("\xfe\xff") # invalid utf-8
    "\\xfe\\xff"

    julia> escape_string(string('\u2135','\0')) # unambiguous
    "ℵ\\0"

    julia> escape_string(string('\u2135','\0','0')) # \0 would be ambiguous
    "ℵ\\x000"

source
`Base.unescape_string` — Function

    unescape_string(str::AbstractString, keep = ())::AbstractString
    unescape_string(io, s::AbstractString, keep = ())::Nothing

General unescaping of traditional C and Unicode escape sequences. The first form returns the escaped string, the second prints the result to `io`. The argument `keep` specifies a collection of characters which (along with backlashes) are to be kept as they are.

The following escape sequences are recognised:

- Escaped backslash (`\\`)
- Escaped double-quote (`\"`)
- Standard C escape sequences (`\a`, `\b`, `\t`, `\n`, `\v`, `\f`, `\r`, `\e`)
- Unicode BMP code points (`\u` with 1-4 trailing hex digits)
- All Unicode code points (`\U` with 1-8 trailing hex digits; max value = 0010ffff)
- Hex bytes (`\x` with 1-2 trailing hex digits)
- Octal bytes (`\` with 1-3 trailing octal digits)

See also `escape_string`.

Examples

    julia> unescape_string("aaa\\nbbb") # C escape sequence
    "aaa\nbbb"

    julia> unescape_string("\\u03c0") # unicode
    "π"

    julia> unescape_string("\\101") # octal
    "A"

    julia> unescape_string("aaa \\g \\n", ['g']) # using `keep` argument
    "aaa \\g \n"

source

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This document was generated with Documenter.jl on Thursday 21 October 2021. Using Julia version 1.7.0-rc2.