Dyalog APL versions

Dyalog APL is released in numbered versions, with approximately one version per year. Each release version is classified as a major (.0) or minor (point) release, depending on whether the major version number is incremented. Major versions are more likely to introduce new features and may spend longer in development.

15.0
Release announcement, notes (pdf)

Version 15.0 was released in June 2016. It added platform-independent portable file functions (, ,  ,  ,  ,  , and  ) and improved support for using APL source code from text files. It also added I-beams for case conversion and creating hashed arrays which behave identically to normal arrays but have faster performance when searched with set functions including Index-Of and Membership.

Dyalog was made free for personal and non-commercial use starting in version 15.0.

Work on the cross-platform session environment RIDE continued, with version 3.0 released simultaneously with Dyalog 15.0.

16.0
Release announcement, notes (pdf)

Version 16.0 was released in June 2017. It added several new primitives as well as tools for working with JSON and CSV files.

The following new primitive functions and operators were added:
 * Where
 * Interval Index
 * Nest
 * Partition, another way to write a function which was previously only accessible with migration level 3
 * At operator
 * Stencil

Additionally, system functions  and   were added to import and export data in common formats. Some JSON support was already present; 16.0 promoted it to a system function.

Work was continued on the RIDE session environment, which was made the default IDE on Linux in addition to macOS. Additionally, the HTMLRenderer and MiServer user interface tools were introduced.

Significant performance improvements were made in structural and selective functions such as Transpose, Catenate, Take, Rotate, and Reverse, and other primitives including Enlist, Encode, and Decode. Work on Dyalog's bytecode compiler was significantly reduced relative to 15.0, a trend which continued with almost no development on the compiler done in 17.0 and later.

17.0
Release announcement, notes

Version 17.0 was released in July 2018. It features significant work on tools for using APL and interfacing with other languages, as well as performance, and a relatively small number of new language features.

Total array ordering (TAO) was added in version 17.0, making it the first APL implementation to order entire arrays rather than cells of a single array. This allows Grade Up, Grade down , and Interval Index to work on nested arrays. Additionally, Unique was extended to allow an argument of any rank by removing duplicate major cells.

17.0 featured improvements to the HTML-based session environment RIDE, and a preliminary version of Link, which was fully released in 17.1. It also improved the positioning of the session's error caret: prior to 17.0 the caret usually pointed to a position further left than the source of an error, while in 17.0 and later it almost always points to the actual primitive or named function or operator which emitted the error, or the beginning of the derived function which did.

Support for packaging APL code as a shared library (for instance a .so or .dll file) for use by other languages was added.

Portable file function support was improved, with changes including new functions  and   to copy and move files.

Version 17.0 implemented substantial performance improvements in many areas. The most important improvements were better use of vector instructions including support for ARM NEON and AVX2 and vectorised comparison functions, simplification of trivial cases for functions, improved Boolean algorithms, and improvements to Replicate, Expand, and Where.

17.1
Release announcement, notes

Version 17.1 was released in October 2019, shortly after the Dyalog '19 user meeting. It contains few new features and almost no performance changes. The primary changes to the language were to add the Link system using, allow running Dyalog through docker containers, and improve cross-platform support for HTMLRenderer. Additionally, Dyalog's licensing was changed to allow non-commercial users to download and run it for free, without applying for a non-commercial license from Dyalog.

The Interval Index primitive was extended to allow duplicate values in the left argument (a feature already present in J, which does not verify that the left argument is sorted).

18.0
Version 18.0 is currently planned for release in 2020. It was developed in parallel with version 17.1, which had very few new features, and includes several new primitives and extensions to existing primitives.

The following new primitive functions and operators are added:
 * Unique Mask
 * Atop operator, sharing a symbol with Rank
 * Over operator
 * Constant operator, sharing a symbol with Commute

Integers greater than 1 are now allowed in the right argument of Where, matching the definition of Indices in other languages. A related extension allows integers greater than 1 in the left argument of Partitioned Enclose, which produce empty partitions in the output. The extension to Partitioned Enclose makes it the first APL partitioning function which can produce empty partitions.

Version 18.0 allows multi-line input in the session using the line editor, and allows control structures to be used in the session. Multi-line input is begun when a dfn, namespace, class, or control structure is begun but not finished on the same line.

New system functions for case folding and mapping and date-time conversion are added.

Initial support for .NET Core, Microsoft's cross-platform successor to the original .NET framework, has been added.