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Generating F# code

Asked 2010-02-02T08:10:49.987
10

T4 is the "official" code generation engine for C#/VB.NET. But F# doesn't support it (this is from April, but I couldn't find any newer mentions). So what is a good way to generate F# code?

EDIT:

I want to implement 2-3 finger trees in F#. I already have implemented them in C#, so this should be a nice comparison. The "digits" and nodes of the tree can be represented as arrays, so

type 't FingerTree = Empty | Single of 't | Deep of 't array * (('t FingerTree) array) lazy * 't array

However, the maximum size of these arrays is very small, so it'd be nice to have

type 't Digit = Digit1 of 't | Digit2 of 't*'t | Digit3 of 't*'t*'t | Digit4 of 't*'t*'t*'t
type 't Node = Node2 of 't FingerTree * 't FingerTree | Node3 of 't FingerTree * 't FingerTree * 't FingerTree 
type 't FingerTree = Empty | Single of 't | Deep of 't Digit * ('t Node) lazy * 't Digit

to avoid bounds checking, etc.

But then writing all functions on Digit and Node by hand becomes more difficult, and it's better to generate them. And a T4-like approach looks perfect for it...

f# code-generation t4 code-templates
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2 Answers

6

It depends what your trying to do. While it's an approach that's not really suitable for generating templates in the way many T4 examples show, in general I would recommend designing a "combinators library" [1] for code generation or language oriented programming tasks in F#. The idea is to design some combinators to represent the code you're try to generate, generating F# source text from combinators, then compiling this via the code DOM.

However often it would be easier simply to write an interpreter for your combinators rather than generating code.

Good examples of combinators in F# are:

[1] http://en.wikipedia.org/wiki/Combinator_library

answered 2010-02-02T09:13:55.600
1

I mostly agree with Robert (though there are certainly some situations where using T4 from F# could be very useful). Anyway, maybe it would be interesting to know why do you want to generate F# code? Then we could maybe suggest some typical functional solution to the problem :-).

answered 2010-02-02T21:45:40.927

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