NEWS.md

Julia v1.9 Release Notes

New language features

• It is now possible to assign to bindings in another module using setproperty!(::Module, ::Symbol, x). ([#44137])
• Slurping in assignments is now also allowed in non-final position. This is handled via Base.split_rest. ([#42902])
• Character literals now support the same syntax allowed in string literals; i.e. the syntax can represent invalid UTF-8 sequences as allowed by the Char type ([#44989]).
• Nested combinations of tuples and named tuples of symbols are now allowed as type parameters ([#46300]).

Language changes

• New builtins getglobal(::Module, ::Symbol[, order]) and setglobal!(::Module, ::Symbol, x[, order]) for reading from and writing to globals. getglobal should now be preferred for accessing globals over getfield. ([#44137])
• The @invoke macro introduced in 1.7 is now exported. Additionally, it now uses Core.Typeof(x) rather than Any when a type annotation is omitted for an argument x so that types passed as arguments are handled correctly. ([#45807])
• The invokelatest function and @invokelatest macro introduced in 1.7 are now exported. ([#45831])

Compiler/Runtime improvements

• The known quadratic behavior of type inference is now fixed and inference uses less memory in general. Certain edge cases with auto-generated long functions (e.g. ModelingToolkit.jl with partial differential equations and large causal models) should see significant compile-time improvements. ([#45276], [#45404])
• Non-concrete call sites can now be union-split to be inlined or statically-resolved even if there are multiple dispatch candidates. This may improve runtime performance in certain situations where object types are not fully known statically but mostly available at runtime (as like Julia-level type inference implementation itself) by statically resolving @nospecialize-d call sites and avoiding excessive compilation. ([#44512])
• All the previous usages of @pure-macro in Base has been replaced with the preferred Base.@assume_effects-based annotations. ([#44776])
• invoke(f, invokesig, args...) calls to a less-specific method than would normally be chosen for f(args...) are no longer spuriously invalidated when loading package precompile files. ([#46010])

Command-line option changes

• In Linux and Windows, --threads=auto now tries to infer usable number of CPUs from the process affinity which is set typically in HPC and cloud environments ([#42340]).
• --math-mode=fast is now a no-op ([#41638]). Users are encouraged to use the @fastmath macro instead, which has more well-defined semantics.
• The --threads command-line option now accepts auto|N[,auto|M] where M specifies the number of interactive threads to create (auto currently means 1) ([#42302]).
• New option --heap-size-hint=<size> gives a memory hint for triggering greedy garbage collection. The size might be specified in bytes, kilobytes(1000k), megabytes(300M), gigabytes(1.5G)

Multi-threading changes

• Threads.@spawn now accepts an optional first argument: :default or :interactive. An interactive task desires low latency and implicitly agrees to be short duration or to yield frequently. Interactive tasks will run on interactive threads, if any are specified when Julia is started ([#42302]).
• Threads started outside the Julia runtime (e.g. from C or Java) can now become able to call into Julia code by calling jl_adopt_thread. This is done automatically when entering Julia code via cfunction or a @ccallable entry point. As a consequence, the number of threads can now change during execution ([#46609]).

Build system changes

New library functions

• Iterators.flatmap was added ([#44792]).
• New helper Splat(f) which acts like x -> f(x...), with pretty printing for inspecting which function f was originally wrapped. ([#42717])
• New pkgversion(m::Module) function to get the version of the package that loaded a given module, similar to pkgdir(m::Module). ([#45607])
• New function stack(x) which generalises reduce(hcat, x::Vector{<:Vector}) to any dimensionality, and allows any iterators of iterators. Method stack(f, x) generalises mapreduce(f, hcat, x) and is efficient. ([#43334])

Library changes

• A known concurrency issue of iterate methods on Dict and other derived objects such as keys(::Dict), values(::Dict), and Set is fixed. These methods of iterate can now be called on a dictionary or set shared by arbitrary tasks provided that there are no tasks mutating the dictionary or set ([#44534]).
• Predicate function negation !f now returns a composed function (!) ∘ f instead of an anonymous function ([#44752]).
• RoundFromZero now works for non-BigFloat types ([#41246]).
• Dict can be now shrunk manually by sizehint! ([#45004]).
• @time now separates out % time spent recompiling invalidated methods ([#45015]).
• eachslice now works over multiple dimensions; eachslice, eachrow and eachcol return a Slices object, which allows dispatching to provide more efficient methods ([#32310]).
• @kwdef is now exported and added to the public API ([#46273])
• An issue with order of operations in fld1 is now fixed ([#28973]).

Standard library changes

Package Manager

LinearAlgebra

• The methods a / b and b \ a with a a scalar and b a vector, which were equivalent to a * pinv(b), have been removed due to the risk of confusion with elementwise division ([#44358]).
• We are now wholly reliant on libblastrampoline (LBT) for calling BLAS and LAPACK. OpenBLAS is shipped by default, but building the system image with other BLAS/LAPACK libraries is not supported. Instead, it is recommended that the LBT mechanism be used for swapping BLAS/LAPACK with vendor provided ones. ([#44360])
• lu now supports a new pivoting strategy RowNonZero() that chooses the first non-zero pivot element, for use with new arithmetic types and for pedagogy ([#44571]).
• normalize(x, p=2) now supports any normed vector space x, including scalars ([#44925]).

Markdown

Printf

• Error messages for bad format strings have been improved, to make it clearer what & where in the format string is wrong. ([#45366])

Random

• randn and randexp now work for any AbstractFloat type defining rand ([#44714]).

REPL

• Meta-e now opens the current input in an editor. The content (if modified) will be executed upon existing the editor.

• The contextual module which is active at the REPL can be changed (it is Main by default), via the REPL.activate(::Module) function or via typing the module in the REPL and pressing the keybinding Alt-m ([#33872]).

• An "IPython mode" which mimics the behaviour of the prompts and storing the evaluated result in Out can be activated with REPL.ipython_mode!(). See the manual for how to enable this at startup.

SparseArrays

Test

• New fail-fast mode for testsets that will terminate the test run early if a failure or error occurs. Set either via the @testset kwarg failfast=true or by setting env var JULIA_TEST_FAILFAST to "true" i.e. in CI runs to request the job failure be posted eagerly when issues occur ([#45317])

Dates

Downloads

Statistics

Sockets

Tar

Distributed

• The package environment (active project, LOAD_PATH, DEPOT_PATH) are now propagated when adding local workers (e.g. with addprocs(N::Int) or through the --procs=N command line flag) ([#43270]).
• addprocs for local workers now accept the env keyword argument for passing environment variables to the workers processes. This was already supported for remote workers ([#43270]).

UUIDs

Unicode

• graphemes(s, m:n) returns a substring of the m-th to n-th graphemes in s ([#44266]).

Mmap

DelimitedFiles

• DelimitedFiles has been promoted from being a standard library to a separate package. It now has to be explicitly installed to be used.

Deprecated or removed

• Unexported splat is deprecated in favor of exported Splat, which has pretty printing of the wrapped function. ([#42717])

External dependencies

Tooling Improvements

• Printing of MethodError and methods (such as from methods(my_func)) are now prettified and color consistent with printing of methods in stacktraces. ([#45069])