Hi Ben,

Thank you for your answer!

I'll give (sub)modules a try.  The examples from the plot library are very 
helpful, I'll peruse them attentively.

I didn't realise that (provide (contract-out)) gave better error messages 
than define/contract.  I'm glad to have chosen to use (provide 
(contract-out)) in my code.


On Monday, March 23, 2020 at 5:16:52 PM UTC+1, Ben Greenman wrote:
> On 3/21/20, unlimitedscolobb <unlimite...@gmail.com <javascript:>> wrote: 
> > Hello, 
> > 
> > I come to Racket from Haskell and so far I am quite happy, as I feel 
> freer 
> > to do some weird stuff from time to time, and I am absolutely in love 
> with 
> > the Lisp-parens syntax. 
> > 
> > As a former Haskeller, one of the first things I tried was Typed Racket. 
> > It worked like a charm for small examples, but started getting in my way 
> > too much as soon as I got to some more advanced stuff (e.g. polymorphic 
> > functions, generics, eval, even apply).  My immediate reaction was 
> ditching 
> > types for contracts, which are rather fine and allow me to use a 
> familiar 
> > language, but I am somewhat worried about the performance penalties 
> > defining everything via define/contract may incur.  Also, it seems weird 
> to 
> > set up runtime contract checks where a simple type annotation would do. 
> > I have no problem with Typed Racket not being able to type every single 
> one 
> > of my functions (after all, I came to Racket to be able to do weird 
> stuff), 
> > but so far I couldn't figure out what would be the best way to mix typed 
> > into two separate files. 
> > 
> > What is the standard practice for mixing typed and untyped code within a 
> > single module?  Submodules?  Typed regions within untyped code?  Maybe 
> > there is an example somewhere I can have a look at? 
> Yep, submodules and typed regions are the two ways to do this. 
> The plot library uses typed submodules in untyped code in a few small 
> places: 
> https://github.com/racket/plot/blob/master/plot-lib/plot/private/common/contract.rkt
> https://github.com/racket/plot/blob/master/plot-lib/plot/private/common/parameter-groups.rkt
> I've done a similar thing to make typed parameters in untyped code. 
> Not sure about best practices, but I definitely prefer keeping typed 
> and untyped code in separate modules. 
> For contracts, though, (provide (contract-out ...)) gives better error 
> messages than define/contract. 

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