Implement titlecase function. Fix #19465.

NEWS.md

@@ -62,6 +62,8 @@ Library improvements
 
   * New `accumulate` and `accumulate!` functions, which generalize `cumsum` and `cumprod`. Also known as a [scan](https://en.wikipedia.org/wiki/Prefix_sum) operation ([#18931]).
 
+  * New `titlecase` function, which capitalizes the first character of each word within a string ([#19469]).
+
 Compiler/Runtime improvements
 -----------------------------
 
@@ -706,8 +708,10 @@ Language tooling improvements
 [#18442]: https://github.com/JuliaLang/julia/issues/18442
 [#18473]: https://github.com/JuliaLang/julia/issues/18473
 [#18839]: https://github.com/JuliaLang/julia/issues/18839
+[#18931]: https://github.com/JuliaLang/julia/issues/18931
 [#18977]: https://github.com/JuliaLang/julia/issues/18977
 [#19018]: https://github.com/JuliaLang/julia/issues/19018
 [#19233]: https://github.com/JuliaLang/julia/issues/19233
 [#19288]: https://github.com/JuliaLang/julia/issues/19288
 [#19305]: https://github.com/JuliaLang/julia/issues/19305
+[#19469]: https://github.com/JuliaLang/julia/issues/19469

base/exports.jl

@@ -873,6 +873,7 @@ export
     strip,
     strwidth,
     summary,
+    titlecase,
     transcode,
     ucfirst,
     unescape_string,

base/strings/basic.jl

@@ -376,7 +376,7 @@ byte_string_classify(s::String) = byte_string_classify(s.data)
 isvalid(::Type{String}, s::Union{Vector{UInt8},String}) = byte_string_classify(s) != 0
 isvalid(s::String) = isvalid(String, s)
 
-## uppercase and lowercase transformations ##
+## uppercase, lowercase, and titlecase transformations ##
 
 """
     uppercase(s::AbstractString)
@@ -402,6 +402,31 @@ julia> lowercase("STRINGS AND THINGS")
 """
 lowercase(s::AbstractString) = map(lowercase, s)
 
+"""
+    titlecase(s::AbstractString)
+
+Capitalizes the first character of each word in `s`.
+
+```jldoctest
+julia> titlecase("the julia programming language")
+"The Julia Programming Language"
+```
+"""
+function titlecase(s::AbstractString)
+    startword = true
+    b = IOBuffer()
+    for c in s
+        if isspace(c)
+            print(b, c)
+            startword = true
+        else
+            print(b, startword ? titlecase(c) : c)
+            startword = false
+        end
+    end
+    return String(take!(b))
+end
+
 """
     ucfirst(s::AbstractString)
 

base/strings/utf8proc.jl

@@ -3,7 +3,7 @@
 # Various Unicode functionality from the utf8proc library
 module UTF8proc
 
-import Base: show, ==, hash, string, Symbol, isless, length, eltype, start, next, done, convert, isvalid, lowercase, uppercase
+import Base: show, ==, hash, string, Symbol, isless, length, eltype, start, next, done, convert, isvalid, lowercase, uppercase, titlecase
 
 export isgraphemebreak
 
@@ -159,6 +159,7 @@ charwidth(c::Char) = Int(ccall(:utf8proc_charwidth, Cint, (UInt32,), c))
 
 lowercase(c::Char) = isascii(c) ? ('A' <= c <= 'Z' ? c + 0x20 : c) : Char(ccall(:utf8proc_tolower, UInt32, (UInt32,), c))
 uppercase(c::Char) = isascii(c) ? ('a' <= c <= 'z' ? c - 0x20 : c) : Char(ccall(:utf8proc_toupper, UInt32, (UInt32,), c))
+titlecase(c::Char) = isascii(c) ? ('a' <= c <= 'z' ? c - 0x20 : c) : Char(ccall(:utf8proc_totitle, UInt32, (UInt32,), c))
 
 ############################################################################
 

doc/stdlib/strings.rst

@@ -407,6 +407,17 @@
        julia> lowercase("STRINGS AND THINGS")
        "strings and things"
 
+.. function:: titlecase(s::AbstractString)
+
+   .. Docstring generated from Julia source
+
+   Capitalizes the first character of each word in ``s``\ .
+
+   .. doctest::
+
+       julia> titlecase("the julia programming language")
+       "The Julia Programming Language"
+
 .. function:: ucfirst(s::AbstractString)
 
    .. Docstring generated from Julia source

test/strings/basic.jl

@@ -392,6 +392,12 @@ end
 @test lcfirst(GenericString("a")) == "a"
 @test ucfirst(GenericString("A")) == "A"
 
+# titlecase
+@test titlecase('lj') == 'Lj'
+@test titlecase("ljubljana") == "Ljubljana"
+@test titlecase("aBc ABC") == "ABc ABC"
+@test titlecase("abcD   EFG\n\thij") == "AbcD   EFG\n\tHij"
+
 # issue # 11464: uppercase/lowercase of GenericString becomes a String
 str = "abcdef\uff\uffff\u10ffffABCDEF"
 @test typeof(uppercase("abcdef")) == String