stan code parsers successfully but fails to compile due to pstream__ not declared error about stanc3 HOT 5 CLOSED

This seems to be caused by the fact that you can't use a function to set vector size. Is this a "deliberate" design choice or a bug?

I was trying to use constants to set the size of my arrays instead of hard coded values (sirFunctions.stan is auto generated). The manual says the way to define constants in stan is:

Constants in Stan are nothing more than nullary (no-argument) functions. For in-
stance, the mathematical constants π and e are represented as nullary functions
named pi() and e(). See Section 41.2 for a list of built-in constants.

So I assumed this would mean you could use such constants when defining vector/array size.

from stanc3.

Thanks for reporting. Models shouldn't translate to C++ and then not compile, so that's a bug.

As far as the language design, the intention is that a function may be used to determine a size for a block variable or local variable as long as the function is constant---it can't change values based on parameters.

The situation that's failing here is using it to define a local variable in a function:

int get_state_dim() { return 13; }
...
real[] ode(real time, real[] state, real[] theta, real[] x_r, int[] x_i) {
    real dydt[get_state_dim()];
...

The problem is that it's not getting a print stream passed in.

In file included from <command-line>:0:0:
./sirStrain.hpp: In member function ‘void sirStrain_model_namespace::sirStrain_model::get_dims(std::vector<std::vector<long unsigned int> >&) const’:
./sirStrain.hpp:2822:40: error: ‘pstream__’ was not declared in this scope
         dims__.push_back(get_state_dim(pstream__));
                                        ^~~~~~~~~

We'll fix this.

from stanc3.

Thanks!

Just as a follow-up. This does work as expected in the transformed data section, but not in the transformed parameters section or within a function.

from stanc3.

Here's a smaller example of both where I get the same failure to compile:

functions {
  int sizer() {
    return 5;
  }
  real[] foo() {
    real x[sizer()];
    return x;
  }
}
transformed data {
  real x[sizer()] = foo();
}
transformed parameters {
  real z[sizer()];
  z = x;
}

from stanc3.

Still an issue in stanc3. Transferring.

from stanc3.