[erlang-questions] No JSON/MAPS interoperability in 17.0?
Richard A. O'Keefe
Mon Mar 17 02:52:08 CET 2014
On 15/03/2014, at 4:20 AM, Fred Hebert wrote:
> 1) it's not just a question of do floating point numbers survive the
> roadtrip, but also integers.
and the ECMAscript specification, my expectation that any
serious language would support integers was so strong that
I completely failed to see that it doesn't. This must make
life extremely "interesting" for people writing compilers
RFC 7159 is explicit: integers up to ±(2**53-1) can be
expected to round-trip (probably, maybe) but no more.
And they cannot be expected to round-trip *as* integers,
but the values should (hopefully, arguably) survive.
> 2) json tags are more or less strings and expect utf-8. Currently, we
> 'support' utf8 atoms but we don't. See
> This doesn't mention what you do in case of trying to encode a map
> which currently uses keys such as '1.0', 1.0, <<"1.0">>, and "1.0" at
> the same time. We currently have 4 data types that will possibly need
> an identical representation while being converted.
> Woops, that doesn't work super well and may in fact cover far less
> than 99% of the cases. We have to consider all the other cases such
> as just 1, 1.0, "1.00", "1.000", ..., and so on.
JSON is not a format for preserving arbitrary Erlang maps.
We can expect a JSON library that's map-aware to offer a
which will _reject_ any map where the keys are not
- all atoms, or
- all strings, or
- all binaries that are valid as UTF-8.
After all, there are other things (like process IDs,
references, and functions) that don't translate to JSON.
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