[m-dev.] Adding standard integer types

[Julien Fischer]

Hi,

This actually a response to Pete's original post rather than to Paul's
comments since my spam filter decided that the former was spam and
deleted it.

On Wed, 17 Sep 2008, Paul Bone wrote:

> On Wed, Sep 17, 2008 at 02:07:50PM +1000, Peter Ross wrote:
>> I'm looking at adding the type int8, int16, int32 and int64 to Mercury
>> and the equivalent unsigned versions.
>>
>> The way I'm currently imagining doing it is to add the following
>> module to the library.
>>
>> :- module stdint.
>> :- interface.
>> :- type int8.
>> :- foreign_type(c, int8, "int8_t").

You will definitely want a can_pass_as_mercury_type attribute for int8,
int16 and int32.  int64 is a bit tricky, on 32-bit machines it will have
to be boxed but it should be unboxed on 64-bit machines.  I suggest
adding a new foreign type attribute:

 	unbox_bit_threshold(<Threshold>)

that causes a foreign_type to be unboxed (passed as a Mercury type)
if sizeof(MR_Word) * 8 >= Threshold.

>> :- func to_int8(int) = int8.
>>
>> I will then add to the runtime the following portable stdint.h renamed
>> to mercury_pstdint.h
>>
>> http://www.azillionmonkeys.com/qed/pstdint.h
>>
>> and add to configure a test for stdint.h and if that doesn't exist we
>> would fall back to using mercury_pstdint.h.
>>
>> Does anyone have any objections/improvements to this plan?

* How will all this be implemented for the other backends?  It should
be fairly trivial for the .NET and Java backends (although unsigned
integers don't exist in the latter.)  The Erlang backend?

* It may be worth considering whether the new types should be implemented
as additional builtin types rather as a library module.

* In any case I don't like the name stdint

Julien.
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