[racket] ":" preferred to "define:"?

[Neil Van Dyke]

Why is ":" preferred to "define:", when usually you're just going to
follow the ":" form with a "define" form?

The Typed Racket Reference says:

> In most cases, use of ":" is preferred to use of "define:".

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[Sam Tobin-Hochstadt]

On Wed, Dec 22, 2010 at 12:36 PM, Neil Van Dyke <ne...@neilvandyke.org> wrote:
> Why is ":" preferred to "define:", when usually you're just going to follow
> the ":" form with a "define" form?
>
> The Typed Racket Reference says:
>
>> In most cases, use of ":" is preferred to use of "define:".

Two reasons:

1. Adding `:' before the definition allows you not to change the
existing untyped definition. This is good for diffs, for example.
2. I greatly prefer the visual appearance using `:' -- `define:'
results in lots of syntactic noise. Similarly, I prefer Haskell-style
type annotation to ML-style in those languages.

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sam th
sa...@ccs.neu.edu

[Eli Barzilay]

40 minutes ago, Sam Tobin-Hochstadt wrote:
> On Wed, Dec 22, 2010 at 12:36 PM, Neil Van Dyke <ne...@neilvandyke.org> wrote:
> > Why is ":" preferred to "define:", when usually you're just going to follow
> > the ":" form with a "define" form?
> >
> > The Typed Racket Reference says:
> >
> >> In most cases, use of ":" is preferred to use of "define:".
>
> Two reasons:
>
> 1. Adding `:' before the definition allows you not to change the
> existing untyped definition. This is good for diffs, for example.

In my course I had a ton of definitions that were very formal but
still in comments:

;; foo : Number -> Number

and switching everything to TS was very easy with the `:' forms.

It goes the other way too -- it's much easier to move code back into
the untyped world by commenting out the `:' forms.

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((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://barzilay.org/ Maze is Life!