F#: is there no UI (like WPF) for it?

Question

i recently saw some videos on F#. it seems it used mainly for Service or Classes only? i see no "F# WPF" app in VS2010 Beta?

Answer 1

Updated according to the link by James Hugard

For now F# will not be used much for GUIs because it is not the most important use case for it. From Don Syme's blog:

In this first supported release, our aim has to be to focus on the core strengths of F# for exploratory programming with F# Interactive, programming with data and implementing parallel and asynchronous components.

Although you can theoretically use F# and the standard GUI libraries if you need a GUI you should use VB or C#:

F# users should use the Visual Studio designer tools to generate C# or Visual Basic code and incorporate those components into their F# applications.

In the longer term "presentation-oriented designer tools that generate F# code" are, according to Syme, "definitely feasible".

Answer 2

You can certainly create GUIs in F# - it's just another .NET language, after all.

Tomas Petricek's book, Functional Programming for the Real World (which I've helped out with a little bit) has various GUI examples. The source code is available to download if you want to see examples.

Admittedly some aspects of GUI programming don't map terribly well to a functional style, as there's a lot of mutation involved, but there are ways and means around that :)

Answer 3

It is a .NET language, so it can use the .NET class library. Which means Winforms, WPF or anything else you might use in C#.

Answer 4

Of course you can use all the WPF classes from F#, too. You can create Windows, controls and everything else from F# and I also sometimes use it from the F# console.

It's not as tightly integrated into Visual Studio as C# or VB yet, but as you can see in the comments, designer support in the future is feasible. I guess we'll have to wait until then (or use other tools).

Answer 5

F# actually has some very nice constructs for creating event-driven UI applications, such as First Class Events, Object Expressions, calling property setters from a constructor e.g., new Form(Text="My Window Title", Width=600, Height=400), and much else.

However, creating a forms designer in VS reqiures a CodeDom for your language. The current CodeDom architecture works great, as long as your language looks exactly like C# or VB; it does not lend itself well to generation of F# code (this from a webcast or interview that I can't locate right now). It also requires partial classes, which IIRC are not supported in the language as of Beta 1. Rather than focus on designer support in the first release, the F# team decided to spend their resources on enhancing other parts of the language, such as asynchronous and parallel programming, etc.

What this means is that you have at least 4 choices for creating UI in F#:

• Write all UI code by hand, which is fine for simple apps;
• Create your F# code as a library to handle the "hard parts," like asynchronous and parallel code, or computation centric code, and call it from C#/VB;
• Create your UI code as a C#/VB library, and both drive it from F# and delegate event handling to F#; or
• Use a DSL or Computation Expression (monad) to simplify building the UI by hand (just discovered this while looking for other links in this answer).

Of these, calling a C# UI library from F# may be the most flexible while still retaining a familar paradigm. But, using computation expressions for quickly building UI by hand is certainly worth looking at.