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Core.AbstractChar
— TypeThe 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
.
Core.Char
— TypeChar(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.
Base.codepoint
— Functioncodepoint(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
).
Base.length
— Methodlength(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
.
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
Base.sizeof
— Methodsizeof(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
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"
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 "
Base.string
— Functionstring(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"
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"
Base.repeat
— Methodrepeat(s::AbstractString, r::Integer)
Repeat a string r
times. This can be written as s^r
.
See also ^
.
Examples
julia> repeat("ha", 3)
"hahaha"
Base.repeat
— Methodrepeat(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"
Base.repr
— Methodrepr(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
.
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"
Core.String
— MethodString(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.
Base.SubString
— TypeSubString(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"
Base.transcode
— Functiontranscode(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.
Examples
julia> str = "αβγ"
"αβγ"
julia> transcode(UInt16, str)
3-element Vector{UInt16}:
0x03b1
0x03b2
0x03b3
julia> transcode(String, transcode(UInt16, str))
"αβγ"
Base.unsafe_string
— Functionunsafe_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.
Base.ncodeunits
— Methodncodeunits(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
.
Base.codeunit
— Functioncodeunit(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
.
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
.
Base.codeunits
— Functioncodeunits(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
Base.ascii
— Functionascii(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.
See also the isascii
predicate to filter or replace non-ASCII characters.
Examples
julia> ascii("abcdeγfgh")
ERROR: ArgumentError: invalid ASCII at index 6 in "abcdeγfgh"
Stacktrace:
[...]
julia> ascii("abcdefgh")
"abcdefgh"
Base.Regex
— TypeRegex(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.
To escape interpolated variables use \Q
and \E
(e.g. Regex("\\Q$x\\E")
)
Base.@r_str
— Macro@r_str -> Regex
Construct a regex, such as r"^[a-z]*$"
, 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 matchingm
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
disablesUCP
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.
Base.SubstitutionString
— TypeSubstitutionString(substr)
Stores the given string substr
as a SubstitutionString
, for use in regular expression substitutions. Most commonly constructed using the @s_str
macro.
Examples
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}
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
.
Examples
julia> msg = "#Hello# from Julia";
julia> replace(msg, r"#(.+)# from (?<from>\w+)" => s"FROM: \g<from>; MESSAGE: \1")
"FROM: Julia; MESSAGE: Hello"
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 \"
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
Base.Docs.@html_str
— Macro@html_str -> Docs.HTML
Create an HTML
object from a literal string.
Examples
julia> html"Julia"
HTML{String}("Julia")
Base.Docs.@text_str
— Macro@text_str -> Docs.Text
Create a Text
object from a literal string.
Examples
julia> text"Julia"
Julia
Base.isvalid
— Methodisvalid(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
Base.isvalid
— Methodisvalid(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
Support for subarray values was added in Julia 1.6.
Base.isvalid
— Methodisvalid(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:
[...]
Base.match
— Functionmatch(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
Base.eachmatch
— Functioneachmatch(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")
Base.RegexMatch
— TypeRegexMatch
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"
Base.keys
— Methodkeys(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.
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
Base.isless
— Methodisless(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
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
Base.cmp
— Methodcmp(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
Base.lpad
— Functionlpad(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"
In Julia 1.7, this function was changed to use textwidth
rather than a raw character (codepoint) count.
Base.rpad
— Functionrpad(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 "
In Julia 1.7, this function was changed to use textwidth
rather than a raw character (codepoint) count.
Base.findfirst
— Methodfindfirst(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
Base.findnext
— Methodfindnext(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
Base.findnext
— Methodfindnext(ch::AbstractChar, string::AbstractString, start::Integer)
Find the next occurrence of character ch
in string
starting at position start
.
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
Base.findlast
— Methodfindlast(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
Base.findlast
— Methodfindlast(ch::AbstractChar, string::AbstractString)
Find the last occurrence of character ch
in string
.
This method requires at least Julia 1.3.
Examples
julia> findlast('p', "happy")
4
julia> findlast('z', "happy") === nothing
true
Base.findprev
— Methodfindprev(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
Base.occursin
— Functionoccursin(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
.
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)}
.
This method requires Julia 1.6 or later.
Base.reverse
— Methodreverse(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"
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"
Base.replace
— Methodreplace(A, old_new::Pair...; [count::Integer])
Return a copy of collection A
where, for each pair old=>new
in old_new
, all occurrences of old
are replaced by new
. Equality is determined using isequal
. If count
is specified, then replace at most count
occurrences in total.
The element type of the result is chosen using promotion (see promote_type
) based on the element type of A
and on the types of the new
values in pairs. If count
is omitted and the element type of A
is a Union
, the element type of the result will not include singleton types which are replaced with values of a different type: for example, Union{T,Missing}
will become T
if missing
is replaced.
See also replace!
, splice!
, delete!
, insert!
.
Version 1.7 is required to replace elements of a Tuple
.
Examples
julia> replace([1, 2, 1, 3], 1=>0, 2=>4, count=2)
4-element Vector{Int64}:
0
4
1
3
julia> replace([1, missing], missing=>0)
2-element Vector{Int64}:
1
0
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.
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"
Base.split
— Functionsplit(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 isfalse
without adlm
argument,true
with adlm
argument.
Examples
julia> a = "Ma.rch"
"Ma.rch"
julia> split(a, ".")
2-element Vector{SubString{String}}:
"Ma"
"rch"
Base.rsplit
— Functionrsplit(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"
Base.strip
— Functionstrip([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.
The method which accepts a predicate function requires Julia 1.2 or later.
Examples
julia> strip("{3, 5}\n", ['{', '}', '\n'])
"3, 5"
Base.lstrip
— Functionlstrip([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.
Examples
julia> a = lpad("March", 20)
" March"
julia> lstrip(a)
"March"
Base.rstrip
— Functionrstrip([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.
Examples
julia> a = rpad("March", 20)
"March "
julia> rstrip(a)
"March"
Base.startswith
— Functionstartswith(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.
Examples
julia> startswith("JuliaLang", "Julia")
true
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.
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
startswith(s::AbstractString, prefix::Regex)
Return true
if s
starts with the regex pattern, prefix
.
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
.
This method requires at least Julia 1.2.
Examples
julia> startswith("JuliaLang", r"Julia|Romeo")
true
Base.endswith
— Functionendswith(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
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.
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
endswith(s::AbstractString, suffix::Regex)
Return true
if s
ends with the regex pattern, suffix
.
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
.
This method requires at least Julia 1.2.
Examples
julia> endswith("JuliaLang", r"Lang|Roberts")
true
Base.contains
— Functioncontains(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
The contains
function requires at least Julia 1.5.
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.
Base.first
— Methodfirst(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≠"
Base.last
— Methodlast(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"
Base.Unicode.uppercase
— Functionuppercase(s::AbstractString)
Return s
with all characters converted to uppercase.
See also lowercase
, titlecase
, uppercasefirst
.
Examples
julia> uppercase("Julia")
"JULIA"
Base.Unicode.lowercase
— Functionlowercase(s::AbstractString)
Return s
with all characters converted to lowercase.
See also uppercase
, titlecase
, lowercasefirst
.
Examples
julia> lowercase("STRINGS AND THINGS")
"strings and things"
Base.Unicode.titlecase
— Functiontitlecase(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"
Base.Unicode.uppercasefirst
— Functionuppercasefirst(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"
Base.Unicode.lowercasefirst
— Functionlowercasefirst(s::AbstractString)
Return s
with the first character converted to lowercase.
See also uppercasefirst
, uppercase
, lowercase
, titlecase
.
Examples
julia> lowercasefirst("Julia")
"julia"
Base.join
— Functionjoin([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"
Base.chop
— Functionchop(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)
""
Base.chomp
— Functionchomp(s::AbstractString) -> SubString
Remove a single trailing newline from a string.
See also chop
.
Examples
julia> chomp("Hello\n")
"Hello"
Base.thisind
— Functionthisind(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]
[...]
Base.nextind
— Functionnextind(str::AbstractString, i::Integer, n::Integer=1) -> Int
Case
n == 1
If
i
is in bounds ins
return the index of the start of the character whose encoding starts after indexi
. In other words, ifi
is the start of a character, return the start of the next character; ifi
is not the start of a character, move forward until the start of a character and return that index. Ifi
is equal to0
return1
. Ifi
is in bounds but greater or equal tolastindex(str)
returnncodeunits(str)+1
. Otherwise throwBoundsError
.Case
n > 1
Behaves like applying
n
timesnextind
forn==1
. The only difference is that ifn
is so large that applyingnextind
would reachncodeunits(str)+1
then each remaining iteration increases the returned value by1
. This means that in this casenextind
can return a value greater thanncodeunits(str)+1
.Case
n == 0
Return
i
only ifi
is a valid index ins
or is equal to0
. OtherwiseStringIndexError
orBoundsError
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
Base.prevind
— Functionprevind(str::AbstractString, i::Integer, n::Integer=1) -> Int
Case
n == 1
If
i
is in bounds ins
return the index of the start of the character whose encoding starts before indexi
. In other words, ifi
is the start of a character, return the start of the previous character; ifi
is not the start of a character, rewind until the start of a character and return that index. Ifi
is equal to1
return0
. Ifi
is equal toncodeunits(str)+1
returnlastindex(str)
. Otherwise throwBoundsError
.Case
n > 1
Behaves like applying
n
timesprevind
forn==1
. The only difference is that ifn
is so large that applyingprevind
would reach0
then each remaining iteration decreases the returned value by1
. This means that in this caseprevind
can return a negative value.Case
n == 0
Return
i
only ifi
is a valid index instr
or is equal toncodeunits(str)+1
. OtherwiseStringIndexError
orBoundsError
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
Base.Unicode.textwidth
— Functiontextwidth(c)
Give the number of columns needed to print a character.
Examples
julia> textwidth('α')
1
julia> textwidth('⛵')
2
textwidth(s::AbstractString)
Give the number of columns needed to print a string.
Examples
julia> textwidth("March")
5
Base.isascii
— Functionisascii(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
For example, isascii
can be used as a predicate function for filter
or replace
to remove or replace non-ASCII characters, respectively:
julia> filter(isascii, "abcdeγfgh") # discard non-ASCII chars
"abcdefgh"
julia> replace("abcdeγfgh", !isascii=>' ') # replace non-ASCII chars with spaces
"abcde fgh"
Base.Unicode.iscntrl
— Functioniscntrl(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
Base.Unicode.isdigit
— Functionisdigit(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
Base.Unicode.isletter
— Functionisletter(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
Base.Unicode.islowercase
— Functionislowercase(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
Base.Unicode.isnumeric
— Functionisnumeric(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
Base.Unicode.isprint
— Functionisprint(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
Base.Unicode.ispunct
— Functionispunct(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
Base.Unicode.isspace
— Functionisspace(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
Base.Unicode.isuppercase
— Functionisuppercase(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
Base.Unicode.isxdigit
— Functionisxdigit(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
Base.escape_string
— Functionescape_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.
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"
Base.unescape_string
— Functionunescape_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"