[mercury-users] constructor class syntax

[Michael Day]

> At this point NU-Prolog compatibility is not very important now, so I
> guess you could put that one down to "hysterical raisons".  We could
> change the language definition to allow `=' instead of `==' in `type'
> definitions, I suppose.

It would be nice. Always better to change today rather than tomorrow.

> I think we will probably end up using `:' for field names.
> Simon Taylor's current implementation is using `::', but
> I think the main reason for that is that `:', which was
> Zoltan's original choice, didn't work because it clashed
> with the use of `:' as module qualifier.
> But I think in the long run we will use `.' as module
> qualifier and `:' as type qualifier, including the `<field_name> : <type>'
> syntax in records.

Ahh yes that would be much better.

> So either the compiler needs to recognize and allow that (ugh),
> or the user needs to use explicit parentheses every time (not
> very nice either).  That's why we chose to use a different
> operator.  We chose `::' because `:: <mode>' was already
> used in combined pred/mode declarations, e.g.

Oh I forgot that use of :: as I rarely write combined declarations. Sounds
like a good justification, and using :: for a namespace qualifier in C++
always felt quite unwieldy.

Thanks for the clarification, I can probably put my syntactical carping to
sleep again for the moment :)

Michael


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