Julia v1.5 Release Notes

New language features

Macro calls @foo {...} can now also be written @foo{...} (without the space) ([#34498]).

Language changes

The interactive REPL now uses "soft scope" for top-level expressions: an assignment inside a scope block such as a for loop 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-scope controls 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 because NTuple refers only to homogeneous tuples (this meaning has not changed) ([#34272]).
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])
The syntax (;) (which was deprecated in v1.4) now creates an empty named tuple ([#30115]).

Multi-threading changes

Build system changes

New library functions

New functions mergewith and mergewith! supersede merge and merge! with combine argument. They don't have the restriction for combine to be a Function and also provide one-argument method that returns a closure. The old methods of merge and merge! are still available for backward compatibility ([#34296]).
The new isdisjoint function indicates whether two collections are disjoint ([#34427]).
Add function ismutable and deprecate isimmutable to check whether something is mutable.([#34652])
include now accepts an optional mapexpr first argument to transform the parsed expressions before they are evaluated ([#34595]).

New library features

Function composition now works also on one argument ∘(f) = f (#34251)
isapprox (or ≈) now has a one-argument "curried" method isapprox(x) which returns a function, like isequal (or ==)` ([#32305]).
Ref{NTuple{N,T}} can be passed to Ptr{T}/Ref{T} ccall signatures ([#34199])

Standard library changes

The @timed macro now returns a NamedTuple ([#34149])
New supertypes(T) function returns a tuple of all supertypes of T ([#34419]).

LinearAlgebra

The BLAS submodule now supports the level-2 BLAS subroutine hpmv! ([#34211]).
normalize now supports multidimensional arrays ([#34239])
lq factorizations can now be used to compute the minimum-norm solution to under-determined systems ([#34350]).

Markdown

Random

REPL

SparseArrays

lu! accepts UmfpackLU as an argument to make use of its symbolic factorization.

Dates

Statistics

Sockets

Distributed

launch_on_machine now supports and parses ipv6 square-bracket notation ([#34430])

Deprecated or removed

External dependencies

Tooling Improvements