NEWS.md
Julia v1.6 Release Notes
========================
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, like 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 an `UInt128` object
are now interpreted as `BigInt` ([#23546]).
Language changes
----------------
* 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`.
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 propogation 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
`@v1.5` unless you have modified `LOAD_PATH`. ([#36434])
Multi-threading changes
-----------------------
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.
Library functions
-----------------
* 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)
New library functions
---------------------
* New function `Base.kron!` and corresponding overloads for various matrix types for performing Kronecker product in-place. ([#31069]).
* New function `Base.Threads.foreach(f, channel::Channel)` for multithreaded `Channel` consumption. ([#34543]).
* 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 `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 library features
--------------------
* The `redirect_*` functions can now be called on `IOContext` objects.
* 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]).
Standard library changes
------------------------
* 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]).
* `Libdl` has been moved to `Base.Libc.Libdl`, however it is still accessible as an stdlib ([#35628]).
* `first` and `last` functions now accept an integer as second argument to get that many
leading or trailing elements of any iterable ([#34868]).
* `intersect` on `CartesianIndices` now returns `CartesianIndices` instead of `Vector{<:CartesianIndex}` ([#36643]).
* `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])
* `push!(c::Channel, v)` now returns channel `c`. Previously, it returned the pushed value `v` ([#34202]).
* `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]).
* A new standard library `TOML` has been added for parsing and printing [TOML files](https://toml.io) ([#37034]).
* The composition operator `∘` now returns a `Base.ComposedFunction` instead of an anonymous function ([#37517]).
* 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]).
* 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])
* Logging (such as `@warn`) no longer catches exceptions in the logger itself ([#36600]).
* 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])
#### 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
* 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.
* 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
#### 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
---------------------
External dependencies
---------------------
Tooling Improvements
---------------------
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