Microsoft previews F# 5

Microsoft is previewing F# 5, and upgrade to the vendor's open source, 'functional-first' language that emphasises interactive, analytical programming.

The preview is available via the .NET 5 Preview SDK or Jupyter Notebooks for .NET. Visual Studio users on Windows will need the .NET 5 preview SDK and Visual Studio Preview.

Aligning with improved .NET support in Jupyter notebooks, a number of improvements in F# 5 including language changes were aimed at making the interactive programming experience better overall. More features in this vein are planned for a future preview.

New and improved F# features, with the intent of improving interactive programming, include easier package references via the new #r "nuget:..." command and enhanced data slicing in three areas: built-in FSharp.Core data types, 3D and 4D arrays in FSharp.Core, and reverse indexes and slicing from the end.

This is in addition to applicative computation expressions that allow for more efficient computations provided that every computation is independent and results are merely accumulated at the end.

When computations are independent of each other, they also are trivially parallelisable. One restriction: Computations are disallowed if they depend on previously computed values.

A new nameof function for logging or validating parameters to functions. By using actual F# symbols instead of string literals, refactoring names over time becomes less difficult. A static class can be opened as if it were a module or namespace. This applies to any static class in .NET or .NET packages, or a developer’s own F#-defined static class.

Other features planned for F# 5 include witness passing for trait constraints with respect to quotations. Suggestions for the language will be tracked in a language suggestions repository.