Question

I’m writing my code as if these are all the same thing, and having no problems, but it’s starting to confuse me when I hover over a function in Visual Studio and see that the type definitions contain 3 different types that I had thought were all the same. Are they the same? Or are they different?

Answer 1

They are the same. See the type abbreviations at the bottom of the FSharp.Core documentation. float = double = System.Double and array<'T> = 'T[]. You can also define your own type abbreviations and use them the same way:

type dbl = double
let (d:dbl) = 1.0

You didn’t ask about it, but note that the one place where type abbreviations might not work quite like you’d expect is measure types; float<_> is defined independently of float, double, and System.Double, and there’s no such thing as a corresponding double<_> or System.Double<_>.