Odd matrix/vector behaviour

[epipping]

Please consider the following example:

#include "muparserx/mpParser.h"

using namespace mup;

int
main()
{
  ParserX  p(pckALL_NON_COMPLEX | pckMATRIX);
  p.EnableAutoCreateVar(true);

  try {
    p.SetExpr("a = zeros(3,3)"); p.Eval();

    var_maptype vmap = p.GetVar();
    for (var_maptype::iterator item = vmap.begin(); item!=vmap.end(); ++item)
      std::cout << item->first << "=" << (Variable&)(*(item->second)) << "\n";
  } catch (mup::ParserError const &e) {
    std::cout << "error: " << e.GetMsg() << std::endl;
  }
}

This works and prints

a={{0, 0, 0}; {0, 0, 0}; {0, 0, 0}} 

I'll change the example a bit now (always just replacing the line p.SetExpr("a = zeros(3,3)"); p.Eval(); with something else and leaving the rest unchanged) and explain why I find the current behaviour to be broken and/or confusing.

1. The way the matrix is printed cannot be read back in:

    p.SetExpr("a={{0, 0, 0}; {0, 0, 0}; {0, 0, 0}}"); p.Eval();

leads to error: Undefined token "; {0, 0, 0}; {0, 0, 0}}" found at position 12.

2. The above suggests I should not be using semicolons -- maybe commas work? Let's try that:

    p.SetExpr("a={{0, 0, 0}, {0, 0, 0}, {0, 0, 0}}"); p.Eval();

Nope: error: Can't evaluate function/operator "Array constructor": Parameter 1 of function "Array constructor" is invalid.

3. Okay, so let's try to construct such a matrix line by line:

    p.SetExpr("a[0]={1, 2, 3}"); p.Eval();
    p.SetExpr("a[1]={4, 5, 6}"); p.Eval();

Hm: a={1, {4, 5, 6}, 3}... That's now what we wanted. Indeed, the [0] is ignored on the first line: replacing a[0]={1,2,3} with a={1,2,3} would have given us the same result.

4. So apparently we need to tell muparserx first that a should be a matrix. So let's first make it a matrix and then assign its rows:

    p.SetExpr("a[0]=zeros(3,3)"); p.Eval();
    p.SetExpr("a[1]={4, 5, 6}"); p.Eval();

Nope, doesn't work: error: Index operator dimension error. -- no idea why.

So basically, I want to be able to populate a matrix, say 3x3 with 9 entries on a single line: without resorting to setting each a[i,j] manually. Is that possible somehow?