Hi, I’m trying to implement a model with constraints based on an NCP-function (continuous & differentiable) and put it into an NLP solver such as IPOPT:

```
@constraint(m, f(x,y) <= 0)
```

where

```
f(x,y) := xy if x+y >= 0
-0.5(x^2 + y^2 ) if x+y < 0
```

Can I get some hints on how to implement such constraints on JuMP if it’s possible?