[racket] Typed Racket frustration

It seems like a small step to start by documenting the ones that
people trip up against multiple times in our mailing lists.

Robby

On Sat, Jan 24, 2015 at 9:07 AM, Matthias Felleisen
<matthias at ccs.neu.edu> wrote:
>
> On Jan 24, 2015, at 1:43 AM, Matthew Butterick wrote:
>
> FWIW, Sam's point that one can't expect every untyped program to work
> without modification is entirely fair.
>
>
> Correct.
>
> But Konrad's point is also fair: if a function like `append` or `hash` works
> differently in TR, then it is, for practical purposes, not the same
> function, even if it relies on the same code.
>
>
> This statement is too coarse. There are at least two senses in which a TR
> function f is distinct from an R function:
>
> 1. f's type restricts the usability of f to a strict "subset" [in the naive
> set-theoretic sense]. This is most likely due to a weakness of the type
> system; the language of "theorems" isn't strong enough to express R's
> intention w/o making the inference rules unsound. [Unlike in the legal
> world, In PL arguments of 'typedness' must be about truly-guilty or
> not-guilty. The rulings are completely impartial and uniform, i.e., totally
> fair.]
>
> 2. f's type ___changes___ the meaning of the code. (That's also possible but
> I don't want to fan the argument that Sam and I have about this.)
>
>
> If it would be superfluous to repeat every TR function in the documentation,
> it still could be valuable to document some of the major departures from
> Racket. I mean, I would read that, for sure ;)
>
>
>
> Actually it would not be superfluous. We just don't have the manpower but
> perhaps it's time to tackle this problem (perhaps in a semi-automated
> manner).
>
> -- Matthias
>
>
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