# What does a function inside brackets and a minus sign mean?

I am working in constraint optimization. And I've just come across this notation.

I'm not sure what this means.

The set I is the set of inequality constraints. I'm not sure what the function in brackets means

• Any more context you can give would be helpful. I don't know about the specific field of constraint optimisation, but that kind of notation in other areas is usually defined ad-hoc. – Patrick Stevens Dec 20 '17 at 23:20

I guess that $[y]^- = \min(y,0)$.
This notation is mentioned in Wikipedia, but with a slight difference: $[y]^- = -\min(y,0)$.
• Other interpretations are possible, namely $\min(\lfloor y\rfloor ,0 )$ and $\min(\text{round}(y),0)$, where $\text{round}$ denotes the closest integer. – Jack D'Aurizio Dec 21 '17 at 1:27