Domains and inequality consistency

Suppose that you have a set defined as:
`x | x >= 0 & f(x) <= 0`

with `dom(f) = {x | x >= 0}`, this implies f(x) cannot be computed if `x >= 0`.
A first idea was to compute a distance as 
```julia
if x < 0
    abs(x)
else
    max(f(x), 0)
end
```

This can result in consistency issues (still haven't formally written down how it appears)