Current develop breaks old code?

Developers
1

Hi!

I have these two functions in Stan:

  matrix slice_m(matrix data, int[] S, int s) {
     int l = sum(S[1:(s-1)]);
     int u = l + S[s];
     return(data[(l+1):u,:]);
   }

  // given as input a 2D matrix of size NxM and a slicing vector S, the
  // output is a 1D array with each slice flattened to a 1D column major
  // ordering.
  real[] to_array_1d_sliced(matrix data, int[] S) {
    int N = dims(data)[1];
    int M = dims(data)[2];
    real res[N*M];
    int rs = 1;

    for(s in 1:size(S)) {
      res[rs : (rs + M*S[s] - 1)] = to_array_1d(slice_m(data, S, s));
      rs = rs + M*S[s];
    }

    return(res);
  }

In the released 2.14.0 this works just fine. In the current develop of cmdstan I get this complaint:

Illegal statement beginning with non-void expression parsed as
res[rs:((rs + (M * S[s])) - 1)]
Not a legal assignment, sampling, or function statement. Note that

  • Assignment statements only allow variables (with optional indexes) on the left;
    if you see an outer function logical_lt (<) with negated (-) second argument,
    it indicates an assignment statement A <- B with illegal left
    side A parsed as expression (A < (-B)).
  • Sampling statements allow arbitrary value-denoting expressions on the left.
  • Functions used as statements must be declared to have void returns

ERROR at line 819

818: for(s in 1:size(S)) {
819: res[rs : (rs + MS[s] - 1)] = to_array_1d(slice_m(data, S, s));
^
820: rs = rs + MS[s];

PARSER EXPECTED: “}”

Is this a new bug and I should file an issue?

Or asked differently: Were there changes to the parser recently?

Best,
Sebastian

2

I hope I am managing these git modules right, but if yes, then this is a bug either with my code which was never valid or this is truly a new bug. I am filing a new stan issue for this to resolve this.

3

yes there were changes to the parser which caused this problem. it’s been fixed and changes have been merged into develop. details here: https://github.com/stan-dev/stan/pull/2256
cheers,
Mitzi