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Type Inference: Does it really help?
f#java

Hi guys,
I'm really excited about diving right into F#. The most exciting thing about F# for me is the perfect type inference. It seems like a huge productivity boost. But now I started to wonder whether it helps much for practical programs.

The basic idea behind F# is, it deduces the types from the functions that are called. So is there really a difference between:

explicitly declaring types: ala java or C#...
SuperEngine engine = new SuperEngine()
engine.doThis(1);
engine.doThat(2);
engine.doSuperStuff(3);

and this?
let engine = SuperEngine.create in
SuperEngine.doThis engine 1
SuperEngine.doThat engine 2
SuperEngine.doSuperStuff engine 3

It seems to me that the type declarations are just moved from one place to another. Since methods cannot be overloaded, methods should probably now be put into appropriate modules.

I'd be ecstatically happy if someone told me that my thinking is all wrong. I'm really looking for a productivity boost, after using Java and C++ for so long...

Thanks very much for your enlightenment.
-Patrick

.

Avoiding type annotations makes it easier to change the type of data. Even in your example (which has very few variables) you need to change two places in the Java code if you update your SuperEngine to a StableEngine.
If you write your F# code in the same way as your Java code, i.e.

1
2
3
4

let engine = new SuperEngine in
  engine.doThis 1;
  engine.doThat 2;
  engine.doSuperStuff 3

then you only need to change the let binding. You may even get away with a simple

1

type SuperEngine = StableEngine

when you do your upgrade, in which case you can leave all your code unchanged.

That's just one advantage. Personally I feel I will have a hard time going back to C++. There is just way too much text you have to write that doesn't do anything at all.

By on 9/20/2008 5:30 AM ()

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