multipleOf fails with some floats

[seagreen]

Specifically it fails this test:

jsonschema_test.go:56: schema.Validate failed to validate good data.
  file: JSON-Schema-Test-Suite/tests/draft4/multipleOf.json
  test case description: by small number
  schema: {"multipleOf": 0.0001}
  test instance description: 0.0075 is multiple of 0.0001
  test data: 0.0075
  result of schema.Validate:
      expected: true
      actual: false
      actual validation errors: [{Value must be a multiple of 0.0001.}]

One thing I could do is multiple both the operator and the operand by some factor of 10 and then turn them both into integers before making the calculation. No idea if that's a good approach or not.

[titanous]

So apparently the floating point modulus function is fucked up. It's the same in all languages I've tried.

The solution is to not implement multipleOf for floats, because apparently computers don't know how to do that.

[seagreen]

Sounds good. I'll disable multipleOf for floats and make a note in the README.

[seagreen]

P.S. I haven't made a note in the README yet, but there's a comment on the multipleOf validator that describes the situation.

[seagreen]

Here's how the Python jsonschema package handle's it. Does this look like a good idea: https://github.com/Julian/jsonschema/blob/master/jsonschema/_validators.py#L115

[titanous]

Yeah, that's an option. I'm entirely unconvinced that multipleOf against floats is meaningful though.

[vlcinsky]

I found multipleOf meaningful, but the jsonschema solution is definitely not watterproof: python-jsonschema/jsonschema#185