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Julia v0.5.0 Release Notes

New language features

  • Generator expressions, e.g. f(i) for i in 1:n (#4470). This returns an iterator that computes the specified values on demand.

  • Broadcasting syntax: f.(args...) is equivalent to broadcast(f, args...) (#15032).

  • Macro expander functions are now generic, so macros can have multiple definitions (e.g. for different numbers of arguments, or optional arguments) (#8846, #9627). However note that the argument types refer to the syntax tree representation, and not to the types of run time values.

  • Varargs functions like foo{T}(x::T...) may now restrict the number of such arguments using foo{T,N}(x::Vararg{T,N}) (#11242).

  • x ∈ X is now a synonym for x in X in for loops and comprehensions, as it already was in comparisons (#13824).

  • PROGRAM_FILE global is now available for determining the name of the running script (#14114).

  • The syntax x.:sym (e.g. Base.:+) is now supported, and x.(:sym) is deprecated (#15032).

  • Function return type syntax function f()::T has been added (#1090). Values returned from a function with such a declaration will be converted to the specified type T.

  • Experimental support for arrays with indexing starting at values different from 1. The array types are expected to be defined in packages, but now Julia provides an API for writing generic algorithms for arbitrary indexing schemes (#16260).

Language changes

  • Each function and closure now has its own type. The captured variables of a closure are fields of its type. Function is now an abstract type, and is the default supertype of functions and closures. All functions, including anonymous functions, are generic and support all features (e.g. keyword arguments). Instead of adding methods to call, methods are added by type using the syntax (::ftype)(...) = .... call is deprecated (#13412).

  • using and import are now case-sensitive even on case-insensitive filesystems (common on Mac and Windows) (#13542).

  • Relational symbols are now allowed as infix operators (#8036).

  • A warning is always given when a method is overwritten (previously, this was done only when the new and old definitions were in separate modules) (#14759).

  • A <: B is parsed as Expr(:(<:), :A, :B) in all cases (#9503). This also applies to the >: operator.

  • Simple 2-argument comparisons like A < B are parsed as calls instead of using the :comparison expression type.

  • The if keyword cannot be followed immediately by a line break (#15763).

  • The built-in NTuple type has been removed; NTuple{N,T} is now implemented internally as Tuple{Vararg{T,N}} (#11242).

Command-line option changes

Compiler/Runtime improvements

  • Machine SIMD types can be represented in Julia as a homogeneous tuple of VecElement (#15244).

Breaking changes

  • Method ambiguities no longer generate warnings when files are loaded, nor do they dispatch to an arbitrarily-chosen method; instead, a call that cannot be resolved to a single method results in a MethodError. (#6190)

  • pmap keyword arguments err_retry=true and err_stop=false are deprecated. Action to be taken on errors can be specified via the on_error keyword argument. Retry is specified via retry_n, retry_on and retry_max_delay.

  • reshape is now defined to always share data with the original array. If a reshaped copy is needed, use copy(reshape(a)) or copy! to a new array of the desired shape (#4211).

  • mapslices will always pass a view, so passing mutating functions will mutate the underlying array (#16260)

  • Local variables and arguments are represented in lowered code as numbered Slot objects instead of as symbols (#15609).

  • The information that used to be in the ast field of the LambdaStaticData type is now divided among the fields code, slotnames, slottypes, slotflags, gensymtypes, rettype, nargs, and isva in the LambdaInfo type (#15609).

  • Juxtaposition of numeric literals ending in . (e.g. 1.x) is no longer allowed (#15731).

Library improvements

  • Strings (#16107):

    • The UTF8String and ASCIIString types have been merged into a single String type (#16058). Use isascii(s) to check whether a string contains only ASCII characters.

    • The basic string construction routines are now string(args...), String(s), unsafe_string(ptr) (formerly bytestring(ptr)), and unsafe_wrap(String, ptr) (formerly pointer_to_string) (#16731).

  • Most of the combinatorics functions have been moved from Base to the Combinatorics.jl package (#13897).

  • Packages:

    • The package system (Pkg) is now based on the libgit2 library, rather than running the git program, increasing performance (especially on Windows) (#11196).

    • Package-development functions like Pkg.tag and Pkg.publish have been moved to an external PkgDev package (#13387).

  • The Base.Test module now has a @testset feature to bundle tests together and delay throwing an error until the end (#13062).

    • The new features are mirrored in the BaseTestNext package for users who would like to use the new functionality on Julia v0.4.

    • The BaseTestDeprecated package provides the old-style handler functionality, for compatibility with code that needs to support both Julia v0.4 and v0.5.

  • The functions remotecall, remotecall_fetch, and remotecall_wait now have the function argument as the first argument to allow for do-block syntax (#13338).

  • cov and cor don't use keyword arguments anymore and are therefore now type stable (#13465).

  • Arrays and linear algebra:

    • All dimensions indexed by scalars are now dropped, whereas previously only trailing scalar dimensions would be omitted from the result (#13612).

    • Dimensions indexed by multidimensional arrays add dimensions. More generally, the dimensionality of the result is the sum of the dimensionalities of the indices (#15431).

    • New normalize and normalize! convenience functions for normalizing vectors (#13681).

    • QR

      • New method for generic QR with column pivoting (#13480).

      • New method for polar decompositions of AbstractVectors (#13681).

    • A new SparseVector type allows for one-dimensional sparse arrays. Slicing and reshaping sparse matrices now return vectors when appropriate. The sparsevec function returns a one-dimensional sparse vector instead of a one-column sparse matrix. (#13440)

    • Rank one update and downdate functions, lowrankupdate, lowrankupdate!, lowrankdowndate, and lowrankdowndate!, for dense Cholesky factorizations (#14243, #14424)

    • All sparse methods now retain provided numerical zeros as structural nonzeros; to drop numerical zeros, use dropzeros! (#14798, #15242).

  • New foreach function for calling a function on every element of a collection when the results are not needed.

  • Cmd(cmd; ...) now accepts new Windows-specific options windows_verbatim (to alter Windows command-line generation) and windows_hide (to suppress creation of new console windows) (#13780).

  • Statistics:

    • Improve performance of quantile (#14413).

    • extrema can now operate over a region (#15550).

  • The new Base.StackTraces module makes stack traces easier to use programmatically (#14469).

  • There is now a default no-op flush(io) function for all IO types (#16403).

  • Concatenating dense and sparse matrices now returns a sparse matrix (#15172).

  • The libjulia library is now properly versioned and installed to the public <prefix>/lib directory, instead of the private <prefix>/lib/julia directory (#16362).

  • System reflection is now more consistently exposed from Sys and not Base. OS_NAME has been replaced by Sys.KERNEL and always reports the name of the kernel (as reported by uname). The @windows_only and @osx family of macros have been replaced with functions such as is_windows() and or is_apple(). There's now also an @static macro that will evaluate the condition of an if-statement at compile time, for when a static branch is required (#16219).

  • Prime number related functions have been moved from Base to the Primes.jl package (#16481).

Deprecated or removed

  • The following function names have been simplified and unified (#13232):

    • get_bigfloat_precision -> precision(BigFloat)

    • set_bigfloat_precision -> setprecision

    • with_bigfloat_precision -> setprecision

    • get_rounding -> rounding

    • set_rounding -> setrounding

    • with_rounding -> setrounding

  • The method A_ldiv_B!(SparseMatrixCSC, StrideVecOrMat) has been deprecated in favor of versions that require the matrix to be in factored form (#13496).

  • Deprecate chol(A,Val{:U/:L}) in favor of chol(A) (#13680).

  • issym is deprecated in favor of issymmetric to match similar functions (ishermitian, ...) (#15192)

  • scale is deprecated in favor of either α*A, Diagonal(x)*A, or A*Diagonal(x). (#15258)

  • xdump is removed, and dump now simply shows the full representation of a value. dump should not be overloaded, since it is for examining concrete structure (#4163).

  • sub and slice have been deprecated in favor of view (#16972)