F# 4.1 brings improvements to the language. It is distributed trough the Microsoft tools for F#, which are stated to ship later this year. This version enables support for struct tuples, interoperation with C# 7 and by-ref returns.
Tuples are commonly used in F#, as the syntax and type inference make them easy to use. They are reference types, stored on the heap. F# 4.1 brings struct tuples, stored on the stack. This have performance benefits for certain scenarios, such as allocating a large number of small tuples.
To support the ValueTuple type, tuple types, tuple expressions and tuple patterns can now be annotated with the struct keyword.
Interoperation with C# 7 also works using the struct keyword.
In addition to tuples, record types and discriminated unions cam also be represented as value types. It required the struct annotation.
F# 4.1 also brings by-ref returns. F# already has support for ref locals but had no support for consuming or generating byref-returning methods.
By-ref returns can also be consumed from a C# method.
In addition to the F# source code on GitHub, the language specifications are also available publicly for more informations.<\/p>\n