Julia v1.5 Release Notes
New language features
- Macro calls
@foo {...}can now also be written@foo{...}(without the space) (#34498). ⨟is now parsed as a binary operator with times precedence. It can be entered in the REPL with\bbsemifollowed by <kbd>TAB</kbd> (#34722).±and∓are now unary operators as well, like+or-. Attention has to be paid in macros and matrix constructors, which are whitespace sensitive, because expressions like[a ±b]now get parsed as[a ±(b)]instead of[±(a, b)](#34200).- Passing an identifier
xby itself as a keyword argument or named tuple element is equivalent tox=x, implicitly using the name of the variable as the keyword or named tuple field name. Similarly, passing ana.bexpression usesbas the keyword or field name (#29333). - Support for Unicode 13.0.0 (via utf8proc 2.5) (#35282).
- The compiler optimization level can now be set per-module using the experimental macro
Base.Experimental.@optlevel n. For code that is not performance-critical, setting this to 0 or 1 can provide significant latency improvements (#34896).
Language changes
- The interactive REPL now uses "soft scope" for top-level expressions: an assignment inside a scope block such as a
forloop automatically assigns to a global variable if one has been defined already. This matches the behavior of Julia versions 0.6 and prior, as well as IJulia. Note that this only affects expressions interactively typed or pasted directly into the default REPL (#28789, #33864). - Outside of the REPL (e.g. in a file), assigning to a variable within a top-level scope block is considered ambiguous if a global variable with the same name exists. A warning is given if that happens, to alert you that the code will work differently than in the REPL. A new command line option
--warn-scopecontrols this warning (#33864). - Converting arbitrary tuples to
NTuple, e.g.convert(NTuple, (1, ""))now gives an error, where it used to be incorrectly allowed. This is becauseNTuplerefers only to homogeneous tuples (this meaning has not changed) (#34272). - The syntax
(;)(which was deprecated in v1.4) now creates an empty named tuple (#30115). @inlinemacro can now be applied to short-form anonymous functions (#34953).- In triple-quoted string literals, whitespace stripping is now done before processing escape sequences instead of after. For example, the syntax
used to yield the string " a\nb", since the single space before""" │ │ │ - a\n b"""bset the indent level. Now the result is "a\n b", since the space beforebis no longer considered to occur at the start of a line. The old behavior is considered a bug (#35001). <:and>:can now be broadcasted over arrays with.<:and.>:(#35085)- The line number of function definitions is now added by the parser as an additional
LineNumberNodeat the start of each function body (#35138). - Statements of the form
a'now get lowered tovar"'"(a)instead ofBase.adjoint(a). This allows for shadowing this function in local scopes, although this is generally discouraged. By default, Base exportsvar"'"as an alias ofBase.adjoint, so custom types should still extendBase.adjoint(#34634).
Compiler/Runtime improvements
- Immutable structs (including tuples) that contain references can now be allocated on the stack, and allocated inline within arrays and other structs (#33886). This significantly reduces the number of heap allocations in some workloads. Code that requires assumptions about object layout and addresses (usually for interoperability with C or other languages) might need to be updated; for example any object that needs a stable address should be a
mutable struct. As a result, Arrayviews no longer allocate (#34126).
Command-line option changes
- Deprecation warnings are no longer shown by default. i.e. if the
--depwarn=...flag is not passed it defaults to--depwarn=no. The warnings are printed from tests run byPkg.test()(#35362). - Color now defaults to on when stdout and stderr are TTYs (#34347).
-t N,--threads Nstarts Julia withNthreads. This option takes precedence overJULIA_NUM_THREADS. The specified number of threads also propagates to worker processes spawned using the-p/--procsor--machine-filecommand line arguments. In order to set number of threads for worker processes spawned withaddprocsuse theexeflagskeyword argument, e.g.addprocs(...; exeflags=`--threads 4`)(#35108).
Multi-threading changes
- Parts of the multi-threading API are now considered stable, with caveats. This includes all documented identifiers from
Base.Threadsexcept theatomic_operations. @threadsnow allows an optional schedule argument. Use@threads :static ...to ensure that the same schedule will be used as in past versions; the default schedule is likely to change in the future.
Build system changes
- The build system now contains a pure-make caching system for expanding expensive operations at the latest possible moment, while still expanding it only once (#35626).
New library functions
- Packages can now provide custom hints to help users resolve errors by using the experimental
Base.Experimental.register_error_hintfunction. Packages that define custom exception types can support hints by calling theBase.Experimental.show_error_hintsfrom theirshowerrormethod (#35094). - The
@ccallmacro has been added to Base. It is a near drop-in replacement forccallwith more Julia-like syntax. It also wraps the newforeigncallAPI for varargs of different types, though it lacks the capability to specify an LLVM calling convention (#32748). - New functions
mergewithandmergewith!supersedemergeandmerge!withcombineargument. They don't have the restriction forcombineto be aFunctionand also provide one-argument method that returns a closure. The old methods ofmergeandmerge!are still available for backward compatibility (#34296). - The new
isdisjointfunction indicates whether two collections are disjoint (#34427). - Add function
ismutableand deprecateisimmutableto check whether something is mutable (#34652). includenow accepts an optionalmapexprfirst argument to transform the parsed expressions before they are evaluated (#34595).- New function
bitreversefor reversing the order of bits in a fixed-width integer (#34791). - New function
bitrotate(x, k)for rotating the bits in a fixed-width integer (#33937). - New function
contains(haystack, needle)and its one argument partially applied form have been added, it acts likeoccursin(needle, haystack)(#35132). - New function
Base.exit_on_sigintis added to control ifInterruptExceptionis thrown by Ctrl-C (#29411). - New function
popat!(vector, index, [default])for removing an element at an arbitrary index from aVector(#35513, #36070).
New library features
- Function composition now works also on one argument
∘(f) = f(#34251). - One argument methods
startswith(x)andendswith(x)have been added, returning partially-applied versions of the functions, similar to existing methods likeisequal(x)(#33193). isapprox(or≈) now has a one-argument "curried" methodisapprox(x)which returns a function, likeisequal(or==) (#32305).@NamedTuple{key1::Type1, ...}macro for convenientNamedTupledeclarations (#34548).Ref{NTuple{N,T}}can be passed toPtr{T}/Ref{T}ccallsignatures (#34199).x::Signed % Unsignedandx::Unsigned % Signedare supported for integer bitstypes.signed(unsigned_type)is supported for integer bitstypes,unsigned(signed_type)has been supported.accumulate,cumsum, andcumprodnow supportTuple(#34654) and arbitrary iterators (#34656).- In
splice!with no replacement, values to be removed can now be specified with an arbitrary iterable (instead of aUnitRange) (#34524). - The
@viewand@viewsmacros now support thea[begin]syntax that was introduced in Julia 1.4 (#35289). openfor files now accepts a keyword argumentlockcontrolling whether file operations will acquire locks for safe multi-threaded access. Setting it tofalseprovides better performance when only one thread will access the file (#35426).- The introspection macros (
@which,@code_typed, etc.) now work withdo-block syntax (#35283) and with dot syntax (#35522). countnow accepts thedimskeyword.- new in-place
count!function similar tosum!. peekis now exported and accepts a type to peek from a stream (#28811).
Standard library changes
- Empty ranges now compare equal, regardless of their startpoint and step (#32348).
- A 1-d
Zipiterator (whereBase.IteratorSizeisBase.HasShape{1}()) with defined length ofnhas now also size of(n,)(instead of throwing an error with truncated iterators) (#29927). - The
@timedmacro now returns aNamedTuple(#34149). - New
supertypes(T)function returns a tuple of all supertypes ofT(#34419). - Views of builtin ranges are now recomputed ranges (like indexing returns) instead of
SubArrays (#26872). - Sorting-related functions such as
sortthat take the keyword argumentslt,rev,orderandbynow do not discardorderifbyorltare passed. In the former case, the order fromorderis used to compare the values ofby(element). In the latter case, any order different fromForwardorReversewill raise an error about the ambiguity. closeon a file (IOStream) can now throw an exception if an error occurs when trying to flush buffered data to disk (#35303).- The large
StridedArrayUnionnow has special printing to avoid printing out its entire contents (#31149).
LinearAlgebra
- The BLAS submodule now supports the level-2 BLAS subroutine
hpmv!(#34211). normalizenow supports multidimensional arrays (#34239).lqfactorizations can now be used to compute the minimum-norm solution to under-determined systems (#34350).sqrt(::Hermitian)now treats slightly negative eigenvalues as zero for nearly semidefinite matrices, and accepts a newrtolkeyword argument for this tolerance (#35057).- The BLAS submodule now supports the level-2 BLAS subroutine
spmv!(#34320). - The BLAS submodule now supports the level-1 BLAS subroutine
rot!(#35124). - New generic
rotate!(x, y, c, s)andreflect!(x, y, c, s)functions (#35124).
Markdown
- In docstrings, a level-1 markdown header "Extended help" is now interpreted as a marker dividing "brief help" from "extended help". The REPL help mode only shows the brief help (the content before the "Extended help" header) by default; prepend the expression with '?' (in addition to the one that enters the help mode) to see the full docstring (#25930).
Random
randn!(::MersenneTwister, ::Array{Float64})is faster, and as a result, for a given state of the RNG, the corresponding generated numbers have changed (#35078).rand!(::MersenneTwister, ::Array{Bool})is faster, and as a result, for a given state of the RNG, the corresponding generated numbers have changed (#33721).- A new faster algorithm ("nearly division less") is used for generating random numbers within a range (#29240). As a result, the streams of generated numbers are changed (for ranges, like in
rand(1:9), and for collections in general, like inrand([1, 2, 3])). Also, for performance, the undocumented property that, given a seed anda, bof typeInt,rand(a:b)produces the same stream on 32 and 64 bits architectures, is dropped.
REPL
SparseArrays
lu!acceptsUmfpackLUas an argument to make use of its symbolic factorization.- The
trimkeyword argument for the functionsfkeep!,tril!,triu!,droptol!,dropzeros!anddropzeroshas been removed in favour of always trimming. Calling these withtrim=falsecould result in invalid sparse arrays.
Dates
- The
epsfunction now acceptsTimeTypetypes (#31487). - The
zerofunction now acceptsTimeTypetypes (#35554).
Statistics
Sockets
- Joining and leaving UDP multicast groups on a
UDPSocketis now supported throughjoin_multicast_group()andleave_multicast_group()(#35521).
Distributed
launch_on_machinenow supports and parses ipv6 square-bracket notation (#34430).
Deprecated or removed
External dependencies
- OpenBLAS has been updated to v0.3.9 (#35113).