[mercury-users] Bit-fields in Mercury

[Jonathan Morgan]

In C/C++ it is fairly common to represent a set of options as
bitfields rather than a set of booleans, like the following:

#define OPT1 1
#define OPT2 2
#define OPT3 4

...

func(..., OPT1 | OPT3);

How (if at all) would this sort of thing be represented in Mercury?
The following is one possible representation.

:- type func_opt ---> func_opt(int).

:- func opt1 = int.
opt1 = 1.
:- func opt2 = int.
opt2 = 2.
:- func opt3 = int.
opt3 = 4.

...

func(..., func_opt(opt1 + opt3)).

This representation is not as type-safe as one might like.  Is there a
better way?

Jon
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