Is F# case sensitive?

Question

I searched here and on the net but no answer.

The reason I ask is, since F# conventions seems like they favor noncapital letters, using BCL types with Pascal conventions look weird in F#, as in:

let stringD = String.Join(" ",[| stringA; stringB |])

Seems like it would be more in the spirit of F# like this:

let stringD = string.join(" ",[| stringA; stringB |])

Answer 1

Surprisingly, the F# Language Specification does not explicitly mention case-sensitivity, but does refer to using different casing for intrinsics/language and user-defined type parameters (5.1.2)

Whilst my experience with F# is limited (beyond Hello World-style apps) I would assume that string.join does not bind to String.Join.

Answer 2

Yes, F# is case-sensitive

let stringD = string.join(" ",[| stringA; stringB |])

Will not work.

Answer 3

Ok, a few things.

First, F# is case-sensitive.

Second, the F# conventions for naming are described in the F# Component Design Guidelines . Briefly, let-bound members inside F# modules use camelCase, but all .NET OO constructs use PascalCase. This is true throughout the F# library.

Finally, in F# string is not a keyword, rather it is both the name of a type abbreviation (for System.String) and the name of a function (that converts to a string). In the expression context of string.Join, the function name takes precedence, which is why string.Join does not work. And because of case-sensitivity, System.String.join would never work (unless e.g. you added an extension member).