What are the equality operators in Stan functions?

Please excuse my newbie question,

model {
  theta = [0.2,0.5,0.3]
  n ~ binomial(N, theta)
  y ~ (how to write the formula?); 

I want y ~ distribution1 if n=0, distribution2 if n>0.

If there is an “equality operator” I might be able to write
y ~ (n==0)*distribution1 + (n!=0)*distribution2
but I cannot find an equality operator or any other logic operators (and, or, xor etc) in the reference.

How is the STANic way to write such a distribution? Many Thanks!

All of the standard logical flow operators are available, so you would do something like:

if (n > 0) {
} else {