[erlang-patches] Serge's ei float patch

[Serge Aleynikov]

On 6/1/2010 9:00 AM, Björn-Egil Dahlberg wrote:
> Oops. I forgot something. (And yet again erl_interface is faced with a
> problem). ei_get_type exposes the internal representation (external
> format) of types. This is a problem. Earlier implementation had its own
> types ... which seemingly was a bad idea ...
>
> Angels are crying for suggesting this but, what do you think of letting
> get_type return ERL_FLOAT_EXT for both ERL_FLOAT_EXT and NEW_FLOAT_EXT?
>
> My aim is to remove the necessity for changing original source code
> dependent on erl_interface, if that is at all possible.
>
> What do you think?

Since ei_get_type() is not implicitly used by the decoding family of 
functions in erl_interface (that rely on the wire-level representation 
of data types) this should be ok (though not pretty).  There's a similar 
situation with ERL_REFERENCE_EXT and ERL_NEW_REFERENCE_EXT, in which 
case ei_get_type() distinguishes the two.

Perhaps a better solution (that could be implemented later after this 
patch is released) would be for ei_get_type() always to return 
ERL_FLOAT_EXT and ERL_REFERENCE_EXT for "old" and "new" corresponding 
representations, but have another flavor of erl_init() that would set 
compatibility mode as a bitmask of flags.  The mode would control 
turning on support for old format as default behavior.

Serge