Returning multiple values from a self-defined function

General
1

Hi! I am not sure if the way I define a function return multiple values and the way I call it makes sense in Stan? Thanks for your help!

real foo(real x) {
  return 1.0, 2.0, 3.0;
}
model{
...
a,b,c = foo(x)
...
}
2

That won’t work. Instead you could change the return type to “vector” (or a real array) and then return that. Which you can then unpack after calling.

3

May I double check with you, so the form like

vector foo(real x) {
  vector[3] u;
  u[1] = 1.0;
  u[2] = 2.0;
  u[3] = 3.0;
  return u;
}

will work?

4

Yep. Or
u = [1, 2, 3]’;