Lazy mpz allocation

[Marc Glisse]

On Fri, 20 Apr 2018, paul zimmermann wrote:

>> Only 0 can have lazy allocation, and I think we document that it isn't
>> legal to put 0 on the denominator.
>
> where is this documented?

That was in a "I think" sentence. Now that I looked a bit more, I don't 
find it... Well, you can't call any mpq function that reads that mpq_t, 
but we don't say you can't write to that mpq_t.

> In mpfr_set_q we use the fact that the user can set q to 1/0
> for example to represent +Inf.

I didn't remember that MPFR did that, but I did remember that some people 
did that. I'll count it as a vote for Marco's patch.

-- 
Marc Glisse