Hi Georges

Thanks for the explanation on 2. Pragmatically, it's just another
contributor to the cost of contract checking.

On 1, I'm (naïvely) baffled as to why the contract should regard an
optional argument as unsupplied when it comes from the default rather than
an explicit passing.

GIven that Racket obliges you to supply a default when declaring an
optional argument, in what sort of situations does the unsupplied case


On Sun, May 7, 2017 at 10:36 PM, Dupéron Georges <
jahvascriptman...@gmail.com> wrote:

> Le dimanche 7 mai 2017 07:27:08 UTC+2, Daniel Prager a écrit :
> > 1. Default argument goes missing from post-condition, leading to an
> > unexpected error ...
> You should use unsupplied-arg? . But I couldn't find a way to get the
> default value from the contract. I would guess that the problem is that the
> contract can be specified separately from the function, and the function
> itself knows the default argument's value. In the general case, extracting
> the default argument's value (without running the default expression
> multiple times) might be tricky.

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