[m-rev.] diff 1/3: Move pointer_equals/2 into the private_builtin module.

[Julien Fischer]

On Fri, 28 Jun 2013, Paul Bone wrote:

> My other two patches in this series are still okay, and the second one is
> still waiting for review.
>
> Move pointer_equals/2 into the private_builtin module.
>
> library/version_hash_table.m:
> library/private_builtin.m:
>    As above.
>
> library/private_builtin.m:
>    Adjust a comment to say that some predicates are implemented in the
>    normal way in this module.
> ---
> library/private_builtin.m    | 40 ++++++++++++++++++++++++++++++++++++++--
> library/version_hash_table.m | 30 +-----------------------------
> 2 files changed, 39 insertions(+), 31 deletions(-)
>
> diff --git a/library/private_builtin.m b/library/private_builtin.m
> index 1dd866d..cd3bffc 100644
> --- a/library/private_builtin.m
> +++ b/library/private_builtin.m
> @@ -23,8 +23,9 @@
> % does not get included in the Mercury library reference manual.
> %
> % Many of the predicates defined in this module are builtin - they do not have
> -% definitions because the compiler generates code for them inline. Some others
> -% are implemented in the runtime.
> +% definitions because the compiler generates code for them inline. A second
> +% group are implemented in the runtime.  Whilst a third group are
> +% implemented normally in this module.
> %
> %-----------------------------------------------------------------------------%
> %-----------------------------------------------------------------------------%
> @@ -118,6 +119,11 @@
>     %
> :- pred typed_compare(comparison_result::uo, T1::in, T2::in) is det.
>
> +    % True if the two objects have the same pointer value in the underlying
> +    % implementation.
> +    %

I suggest something along the lines of:

      True iff the the two terms occupy the same address in memory.
      This is useful as a cheap test of equality when implmenting
      user-defined equality.

(Can I object to the name pointer_equals on the grounds that only a
minority of our current target languages actually have a notion of
pointers?  ;-) )


> +:- pred pointer_equals(T::in, T::in) is semidet.
> +

I suggest s/pointer_equals/pointer_equal/

(Likewise, version_hash_table.equals/2 should really have been called
version_hash_table.equal/2 for the purposes of consistency with the
rest of the stdlib.)

Cheers,
Julien.