Question

is f# records is the same as .net struct? I saw people talk about f# struct,are they use this term interchangable with F# records? Like in FSharp runs my algorithm slower than Python, talking about using struct as dictionary key but with code type Tup = {x: int; y: int} Why is this faster than a tuple as a dictionary key in the link above?

Answer 1

No, in fact, a record type in F# is a reference type just with special functional programming features like pattern matching on properties, easier immutability, and better type inference.

I think Laurent’s speedup must have been for other reasons, because we can prove that Tup is not a ValueType:

type Tup = {x: int; y: int}
typeof<Tup>.BaseType = typeof<System.Object> //true

Whereas

type StructType = struct end
typeof<StructType>.BaseType = typeof<System.ValueType> //true
typeof<StructType>.BaseType = typeof<System.Object> //false