Problem with floating-point exponent

[ptal]

"Exported" from Gecode/gecode#164 with further analysis of the issue.

The .mzn:

float: x;
var float: y;
constraint x > y;

The .dzn:

 x = 2.0e-5;

The error:

  File "/home/ptalbot/.local/lib/python3.10/site-packages/minizinc/instance.py", line 100, in __init__
    self.analyse()
  File "/home/ptalbot/.local/lib/python3.10/site-packages/minizinc/instance.py", line 584, in analyse
    output = self._driver._run(["--model-interface-only"] + files, self._solver)
  File "/home/ptalbot/.local/lib/python3.10/site-packages/minizinc/driver.py", line 232, in _run
    for _ in decode_json_stream(output.stdout):
  File "/home/ptalbot/.local/lib/python3.10/site-packages/minizinc/json.py", line 90, in decode_json_stream
    raise error_from_stream_obj(obj)
minizinc.error.MiniZincError: unexpected token `e'

I checked the definition of the grammar but I didn't find anything wrong, and I don't think it's relevant to the grammar actually.

• When I try with x = 2.0e-4 it works.
• When I try with x = 0.000000003125; it doesn't work and gives the same error about the e syntax.

I run the latest version 0.9.0 and MiniZinc 2.7.3

[Dekker1]

This problem occurs because the JSON parser in MiniZinc does not correctly parse floating point literals.

A minimal example is to only declare x:

float: x;

and use the following JSON data file:

{ "x": 2e-5 }

Since your data file is already in DZN format the easy workaround is to not have MiniZinc Python parse the data.

I will move this issue to the compiler repository, and solve it.