Hi, Stanimals,

I just thought a small question and I look for your ideas.

In Stan, the contained parameters, for example, if \sum_{i=1}^{p}c_i = 1, we may use simplex to define the vector c like

```
simplex[p] c;
```

After that, if I want to define another parameter vector \alpha such that c^T \alpha=0, is there any good suggestion to define such a constrained parameter?

Many thanks!!