========================
New language features
---------------------
* Types written with `where` syntax can now be used to define constructors, e.g.
`(Foo{T} where T)(x) = ...`.
* `<--` and `<-->` are now available as infix operators, with the same precedence
and associativity as other arrow-like operators ([36666]).
* Compilation and type inference can now be enabled or disabled at the module level
using the experimental macro `Base.Experimental.compiler_options` ([37041]).
* The library name passed to `ccall` or `ccall` can now be an expression involving
global variables and function calls. The expression will be evaluated the first
time the `ccall` executes ([36458]).
* `ꜛ` (U+A71B), `ꜜ` (U+A71C) and `ꜝ` (U+A71D) can now also be used as operator
suffixes. They can be tab-completed from `\^uparrow`, `\^downarrow` and `\^!` in the REPL
([37542]).
* Standalone "dotted" operators now get parsed as `Expr(:., :op)`, which gets lowered to
`Base.BroadcastFunction(op)`. This means `.op` is functionally equivalent to
`(x...) -> (op).(x...)`, which can be useful for passing the broadcasted version of an
operator to higher-order functions, for example `map(.*, A, B)` for an elementwise
product of two arrays of arrays ([37583]).
* The syntax `import A as B` (plus `import A: x as y`, `import A.x as y`, and `using A: x as y`)
can now be used to rename imported modules and identifiers ([1255]).
* Unsigned literals (starting with `0x`) which are too big to fit in a `UInt128` object
are now interpreted as `BigInt` ([23546]).
* It is now possible to use `...` on the left-hand side of assignments for taking any
number of items from the front of an iterable collection, while also collecting the rest,
for example `a, b... = [1, 2, 3]`. This syntax is implemented using `Base.rest`,
which can be overloaded to customize its behavior for different collection types
([37410]).
Language changes
----------------
* The postfix conjugate transpose operator `'` now accepts Unicode modifiers as
suffixes, so e.g. `a'ᵀ` is parsed as `var"'ᵀ"(a)`, which can be defined by the
user. `a'ᵀ` parsed as `a' * ᵀ` before, so this is a minor breaking change ([37247]).
* Macros that return `:quote` expressions (e.g. via `Expr(:quote, ...)`) were previously
able to work without escaping (`esc(...)`) their output when needed. This has been
corrected, and now `esc` must be used in these macros as it is in other macros ([37540]).
* The `-->` operator now lowers to a `:call` expression, so it can be defined as
a function like other operators. The dotted version `.-->` is now parsed as well.
For backwards compatibility, `-->` still parses using its own expression head
instead of `:call`.
* The `a[begin, k]` syntax now calls `firstindex(a, 1)` rather than `first(axes(a, 1))` ([35779]),
but the former now defaults to the latter for any `a` ([38742]).
* `⌿` (U+233F) and `¦` (U+00A6) are now infix operators with times-like and plus-like precedence,
respectively. Previously they were parsed as identifier characters ([37973]).
Compiler/Runtime improvements
-----------------------------
* All platforms can now use `executable_path` within `jl_load_dynamic_library()`.
This allows executable-relative paths to be embedded within executables on all
platforms, not just MacOS, which the syntax is borrowed from ([35627]).
* Constant propagation now occurs through keyword arguments ([35976]).
* The precompilation cache is now created atomically ([36416]). Invoking _n_
Julia processes simultaneously may create _n_ temporary caches.
Command-line option changes
---------------------------
* There is no longer a concept of "home project": starting `julia --project=dir`
is now exactly equivalent to starting `julia` and then doing `pkg> activate
$dir` and `julia --project` is exactly equivalent to doing that where
`dir = Base.current_project()`. In particular, this means that if you do
`pkg> activate` after starting `julia` with the `--project` option (or with
`JULIA_PROJECT` set) it will take you to the default active project, which is
`v1.6` unless you have modified `LOAD_PATH` ([36434]).
Multi-threading changes
-----------------------
* Locks now automatically inhibit finalizers from running, to avoid deadlock ([38487]).
* New function `Base.Threads.foreach(f, channel::Channel)` for multithreaded `Channel` consumption ([34543]).
Build system changes
--------------------
* Windows Installer now has the option to 'Add Julia to Path'. To unselect this option
from the commandline simply remove the tasks you do not want to be installed: e.g.
`./julia-installer.exe /TASKS="desktopicon,startmenu,addtopath"`, adds a desktop
icon, a startmenu group icon, and adds Julia to system PATH.
New library functions
---------------------
* New function `Base.kron!` and corresponding overloads for various matrix types for performing Kronecker
product in-place ([31069]).
* New function `Base.readeach(io, T)` for iteratively performing `read(io, T)` ([36150]).
* `Iterators.map` is added. It provides another syntax `Iterators.map(f, iterators...)`
for writing `(f(args...) for args in zip(iterators...))`, i.e. a lazy `map` ([34352]).
* New function `sincospi` for simultaneously computing `sinpi(x)` and `cospi(x)` more
efficiently ([35816]).
* New function `cispi(x)` for more accurately computing `cis(pi * x)` ([38449]).
* New function `addenv` for adding environment mappings into a `Cmd` object, returning the new `Cmd` object.
* New function `insorted` for determining whether an element is in a sorted collection or not ([37490]).
* New function `Base.rest` for taking the rest of a collection, starting from a specific
iteration state, in a generic way ([37410]).
New library features
--------------------
* The `redirect_*` functions now accept `devnull` to discard all output redirected to it, and as an empty
input ([36146]).
* The `redirect_*` functions can now be called on `IOContext` objects ([36688]).
* `findfirst`, `findnext`, `findlast`, and `findall` now support `AbstractVector{<:Union{Int8,UInt8}}`
(pattern, array) arguments ([37283]).
* New constructor `NamedTuple(iterator)` that constructs a named tuple from a key-value pair iterator.
* A new `reinterpret(reshape, T, a::AbstractArray{S})` reinterprets `a` to have eltype `T` while potentially
inserting or consuming the first dimension depending on the ratio of `sizeof(T)` and `sizeof(S)`.
* New `append!(vector, collections...)` and `prepend!(vector, collections...)` methods accept multiple
collections to be appended or prepended ([36227]).
* `keys(io::IO)` has been added, which returns all keys of `io` if `io` is an `IOContext` and an empty
`Base.KeySet` otherwise ([37753]).
* `count` now accepts an optional `init` argument to control the accumulation type ([37461]).
* New method `occursin(haystack)` that returns a function that checks whether its argument occurs in
`haystack` ([38475]).
* New methods `∉(collection)`, `∋(item)`, and `∌(item)` returning corresponding containment-testing
functions ([38475]).
* The `nextprod` function now accepts tuples and other array types for its first argument ([35791]).
* The `reverse(A; dims)` function for multidimensional `A` can now reverse multiple dimensions at once
by passing a tuple for `dims`, and defaults to reversing all dimensions; there is also a multidimensional
in-place `reverse!(A; dims)` ([37367]).
* The function `isapprox(x,y)` now accepts the `norm` keyword argument also for numeric (i.e., non-array)
arguments `x` and `y` ([35883]).
* `ispow2(x)` now supports non-`Integer` arguments `x` ([37635]).
* `view`, `view`, and `views` now work on `AbstractString`s, returning a `SubString` when appropriate ([35879]).
* All `AbstractUnitRange{<:Integer}`s now work with `SubString`, `view`, `view` and `views` on strings ([35879]).
* `sum`, `prod`, `maximum`, and `minimum` now support `init` keyword argument ([36188], [35839]).
* `unique(f, itr; seen=Set{T}())` now allows you to declare the container type used for
keeping track of values returned by `f` on elements of `itr` ([36280]).
* `first` and `last` functions now accept an integer as second argument to get that many
leading or trailing elements of any iterable ([34868]).
* `CartesianIndices` now supports step different from `1`. It can also be constructed from three
`CartesianIndex`es `I`, `S`, `J` using `I:S:J`. `step` for `CartesianIndices` now returns a
`CartesianIndex` ([37829]).
* `RegexMatch` objects can now be probed for whether a named capture group exists within it through `haskey()` ([36717]).
* For consistency `haskey(r::RegexMatch, i::Integer)` has also been added and returns if the capture group
for `i` exists ([37300]).
Standard library changes
------------------------
* A new standard library `TOML` has been added for parsing and printing [TOML files](https://toml.io) ([#37034]).
* A new standard library `Downloads` has been added, which replaces the old `Base.download` function with
`Downloads.download`, providing cross-platform, multi-protocol, in-process download functionality implemented
with [libcurl](https://curl.haxx.se/libcurl/) ([#37340]).
* `Libdl` has been moved to `Base.Libc.Libdl`, however it is still accessible as an stdlib ([35628]).
* To download artifacts lazily, `LazyArtifacts` now must be explicitly listed as a dependency, to avoid needing the
support machinery to be available when it is not commonly needed ([37844]).
* It is no longer possible to create a `LinRange`, `StepRange`, or `StepRangeLen` with a `<: Integer` eltype but
non-integer step ([32439]).
* `intersect` on `CartesianIndices` now returns `CartesianIndices` instead of `Vector{<:CartesianIndex}` ([36643]).
* `push!(c::Channel, v)` now returns channel `c`. Previously, it returned the pushed value `v` ([34202]).
* The composition operator `∘` now returns a `Base.ComposedFunction` instead of an anonymous function ([37517]).
* Logging (such as `warn`) no longer catches exceptions in the logger itself ([36600]).
* `time` now reports if the time presented included any compilation time, which is shown as a percentage ([37678]).
* `varinfo` can now report non-exported objects within modules, look recursively into submodules, and return a sorted
results table ([38042]).
* `testset` now supports the option `verbose` to show the test result summary
of the children even if they all pass ([33755]).
* In `LinearIndices(::Tuple)` and `CartesianIndices(::Tuple)`, integers (as opposed to ranges of integers) in the
argument tuple now consistently describe 1-based ranges, e.g, `CartesianIndices((3, 1:3))` is equivalent to
`CartesianIndices((1:3, 1:3))`. This is how tuples of integers have always been documented to work, but a
bug had caused erroneous behaviors with heterogeneous tuples containing both integers and ranges ([37829], [37928]).
Package Manager
* `pkg> precompile` is now parallelized through depth-first precompilation of dependencies. Errors will only throw for
direct dependencies listed in the `Project.toml`.
* `pkg> precompile` is now automatically triggered whenever Pkg changes the active manifest. Auto-precompilation will
remember if a package has errored within the given environment and will not retry until it changes.
Auto-precompilation can be gracefully interrupted with a `ctrl-c` and disabled by setting the environment variable
`JULIA_PKG_PRECOMPILE_AUTO=0`.
* The `Pkg.BinaryPlatforms` module has been moved into `Base` as `Base.BinaryPlatforms` and heavily reworked.
Applications that want to be compatible with the old API should continue to import `Pkg.BinaryPlatforms`,
however new users should use `Base.BinaryPlatforms` directly ([37320]).
* The `Pkg.Artifacts` module has been imported as a separate standard library. It is still available as
`Pkg.Artifacts`, however starting from Julia v1.6+, packages may import simply `Artifacts` without importing
all of `Pkg` alongside ([37320]).
LinearAlgebra
* New method `LinearAlgebra.issuccess(::CholeskyPivoted)` for checking whether pivoted Cholesky factorization was
successful ([36002]).
* `UniformScaling` can now be indexed into using ranges to return dense matrices and vectors ([24359]).
* New function `LinearAlgebra.BLAS.get_num_threads()` for getting the number of BLAS threads ([36360]).
* `(+)(::UniformScaling)` is now defined, making `+I` a valid unary operation ([36784]).
* Instances of `UniformScaling` are no longer `isequal` to matrices. Previous
behaviour violated the rule that `isequal(x, y)` implies `hash(x) == hash(y)`.
* Transposing `*Triangular` matrices now returns matrices of the opposite triangular type, consistently
with `adjoint!(::*Triangular)` and `transpose!(::*Triangular)`. Packages containing methods with, e.g.,
`Adjoint{<:Any,<:LowerTriangular{<:Any,<:OwnMatrixType}}` should replace that by
`UpperTriangular{<:Any,<:Adjoint{<:Any,<:OwnMatrixType}}` in the method signature ([38168]).
Markdown
Printf
* Complete overhaul of internal code to use the ryu float printing algorithms (from Julia 1.4); leads to
consistent 2-5x performance improvements.
* New `Printf.tofloat` function allowing custom float types to more easily integrate with Printf formatting
by converting their type to `Float16`, `Float32`, `Float64`, or `BigFloat`.
* New `Printf.format"..."` and `Printf.Format(...)` functions that allow creating `Printf.Format` objects
that can be passed to `Printf.format` for easier dynamic printf formatting.
* `Printf.format(f::Printf.Format, args...)` as a non-macro function that applies a printf format `f` to
provided `args`.
Random
REPL
* The `AbstractMenu` extension interface of `REPL.TerminalMenus` has been extensively
overhauled. The new interface does not rely on global configuration variables, is more
consistent in delegating printing of the navigation/selection markers, and provides
improved support for dynamic menus. These changes are compatible with the previous
(deprecated) interface, so are non-breaking.
The new API offers several enhancements:
+ Menus are configured in their constructors via keyword arguments.
+ For custom menu types, the new `Config` and `MultiSelectConfig` replace the global `CONFIG` `Dict`.
+ `request(menu; cursor=1)` allows you to control the initial cursor position in the menu (defaults to first item).
+ `MultiSelectMenu` allows you to pass a list of initially-selected items with the `selected` keyword argument.
+ `writeLine` was deprecated to `writeline`, and `writeline` methods are not expected to print the cursor indicator.
The old `writeLine` continues to work, and any of its method extensions should print the cursor indicator as before.
+ `printMenu` has been deprecated to `printmenu`, and it both accepts a state input and returns a state output
that controls the number of terminal lines erased when the menu is next refreshed. This plus related changes
makes `printmenu` work properly when the number of menu items might change depending on user choices.
+ `numoptions`, returning the number of items in the menu, has been added as an alternative to implementing `options`.
+ `suppress_output` (primarily a testing option) has been added as a keyword argument to `request`,
rather than a configuration option.
* Tab completion now supports runs of consecutive sub/superscript characters,
e.g. `\^(3)` tab-completes to `⁽³⁾` ([38649]).
* Windows REPL now supports 24-bit colors, by correctly interpreting virtual terminal escapes.
SparseArrays
* Display large sparse matrices with a Unicode "spy" plot of their nonzero patterns,
and display small sparse matrices by an `Matrix`-like 2d layout of their contents ([33821]).
* New convenient `spdiagm([m, n,] v::AbstractVector)` methods which call
`spdiagm([m, n,] 0 => v)`, consistently with their dense `diagm` counterparts ([37684]).
Dates
* `Quarter` period is defined ([35519]).
* `canonicalize` can now take `Period` as an input ([37391]).
* Zero-valued `FixedPeriod`s and `OtherPeriod`s now compare equal, e.g.,
`Year(0) == Day(0)`. The behavior of non-zero `Period`s is not changed ([37486]).
Statistics
Sockets
Distributed
* Now supports invoking Windows workers via ssh (via new keyword argument `shell=:wincmd` in `addprocs`) ([30614]).
* Other new keyword arguments in `addprocs`: `ssh` to specify the ssh client path, `env` to pass environment
variables to workers, and `cmdline_cookie` to work around an ssh problem with Windows workers that run older
(pre-ConPTY) versions of Windows, Julia or OpenSSH ([30614]).
UUIDs
* Change `uuid1` and `uuid4` to use `Random.RandomDevice()` as default random number generator ([35872]).
* Added `parse(::Type{UUID}, ::AbstractString)` method.
Mmap
* On Unix systems, the `Mmap.madvise!` function (along with OS-specific `Mmap.MADV_*`
constants) has been added to give advice on handling of memory-mapped arrays ([37369]).
Deprecated or removed
---------------------
* The `Base.download` function has been deprecated (silently, by default) in favor of the new `Downloads.download`
standard library function ([37340]).
* The `Base.Grisu` code has been officially removed (float printing was switched to the ryu algorithm code in 1.4).
The code is available from [JuliaAttic](https://github.com/JuliaAttic/Grisu.jl) if needed.
External dependencies
---------------------
Tooling Improvements
---------------------
<!--- generated by NEWS-update.jl: -->
[1255]: https://github.com/JuliaLang/julia/issues/1255
[23546]: https://github.com/JuliaLang/julia/issues/23546
[24359]: https://github.com/JuliaLang/julia/issues/24359
[30614]: https://github.com/JuliaLang/julia/issues/30614
[31069]: https://github.com/JuliaLang/julia/issues/31069
[32439]: https://github.com/JuliaLang/julia/issues/32439
[33755]: https://github.com/JuliaLang/julia/issues/33755
[33821]: https://github.com/JuliaLang/julia/issues/33821
[34202]: https://github.com/JuliaLang/julia/issues/34202
[34352]: https://github.com/JuliaLang/julia/issues/34352
[34543]: https://github.com/JuliaLang/julia/issues/34543
[34868]: https://github.com/JuliaLang/julia/issues/34868
[35519]: https://github.com/JuliaLang/julia/issues/35519
[35627]: https://github.com/JuliaLang/julia/issues/35627
[35628]: https://github.com/JuliaLang/julia/issues/35628
[35779]: https://github.com/JuliaLang/julia/issues/35779
[35791]: https://github.com/JuliaLang/julia/issues/35791
[35816]: https://github.com/JuliaLang/julia/issues/35816
[35839]: https://github.com/JuliaLang/julia/issues/35839
[35872]: https://github.com/JuliaLang/julia/issues/35872
[35879]: https://github.com/JuliaLang/julia/issues/35879
[35883]: https://github.com/JuliaLang/julia/issues/35883
[35976]: https://github.com/JuliaLang/julia/issues/35976
[36002]: https://github.com/JuliaLang/julia/issues/36002
[36146]: https://github.com/JuliaLang/julia/issues/36146
[36150]: https://github.com/JuliaLang/julia/issues/36150
[36188]: https://github.com/JuliaLang/julia/issues/36188
[36227]: https://github.com/JuliaLang/julia/issues/36227
[36280]: https://github.com/JuliaLang/julia/issues/36280
[36360]: https://github.com/JuliaLang/julia/issues/36360
[36416]: https://github.com/JuliaLang/julia/issues/36416
[36434]: https://github.com/JuliaLang/julia/issues/36434
[36458]: https://github.com/JuliaLang/julia/issues/36458
[36600]: https://github.com/JuliaLang/julia/issues/36600
[36643]: https://github.com/JuliaLang/julia/issues/36643
[36666]: https://github.com/JuliaLang/julia/issues/36666
[36688]: https://github.com/JuliaLang/julia/issues/36688
[36717]: https://github.com/JuliaLang/julia/issues/36717
[36784]: https://github.com/JuliaLang/julia/issues/36784
[37034]: https://github.com/JuliaLang/julia/issues/37034
[37041]: https://github.com/JuliaLang/julia/issues/37041
[37247]: https://github.com/JuliaLang/julia/issues/37247
[37283]: https://github.com/JuliaLang/julia/issues/37283
[37300]: https://github.com/JuliaLang/julia/issues/37300
[37320]: https://github.com/JuliaLang/julia/issues/37320
[37340]: https://github.com/JuliaLang/julia/issues/37340
[37367]: https://github.com/JuliaLang/julia/issues/37367
[37369]: https://github.com/JuliaLang/julia/issues/37369
[37391]: https://github.com/JuliaLang/julia/issues/37391
[37410]: https://github.com/JuliaLang/julia/issues/37410
[37461]: https://github.com/JuliaLang/julia/issues/37461
[37486]: https://github.com/JuliaLang/julia/issues/37486
[37490]: https://github.com/JuliaLang/julia/issues/37490
[37517]: https://github.com/JuliaLang/julia/issues/37517
[37540]: https://github.com/JuliaLang/julia/issues/37540
[37542]: https://github.com/JuliaLang/julia/issues/37542
[37583]: https://github.com/JuliaLang/julia/issues/37583
[37635]: https://github.com/JuliaLang/julia/issues/37635
[37678]: https://github.com/JuliaLang/julia/issues/37678
[37684]: https://github.com/JuliaLang/julia/issues/37684
[37753]: https://github.com/JuliaLang/julia/issues/37753
[37829]: https://github.com/JuliaLang/julia/issues/37829
[37844]: https://github.com/JuliaLang/julia/issues/37844
[37973]: https://github.com/JuliaLang/julia/issues/37973
[38042]: https://github.com/JuliaLang/julia/issues/38042
[38062]: https://github.com/JuliaLang/julia/issues/38062
[38168]: https://github.com/JuliaLang/julia/issues/38168
[38449]: https://github.com/JuliaLang/julia/issues/38449
[38475]: https://github.com/JuliaLang/julia/issues/38475
[38487]: https://github.com/JuliaLang/julia/issues/38487
[38649]: https://github.com/JuliaLang/julia/issues/38649
[38742]: https://github.com/JuliaLang/julia/issues/38742