On Saturday, 4 November 2017 at 06:08:22 UTC, Jonathan M Davis
wrote:
Heck, take a really simply one like sqrt. All you have to check
in the out contract is the return value. You have no idea what
was passed in. So, how would you write an out contract
verifying that you got the correct number? If you also had
access to the input, then you could do the reverse operation by
squaring the result to see if it matched the input (assuming of
course that floating point rounding errors don't make that not
work), but you don't have access to the input.
I don't think I've ever written an out contract, so I am inclined
to agree with you. However, there is a sqrt example for integers
in the official docs, it does access its input:
https://dlang.org/spec/contracts.html#pre_post_contracts
long square_root(long x)
in
{
assert(x >= 0);
}
out (result)
{
assert((result * result) <= x && (result+1) * (result+1) > x);
}
