[m-rev.] for review 3/3: Update psqueue.m's interface to match other library

[Julien Fischer]

On Sun, 7 Dec 2014, Paul Bone wrote:

> This patch is difficult to read as I've also re-ordered the clauses to match
> the order of declrations in the file's interface.  I will attach the
> complete psqueue.m file.
>
> ---
> Update psqueue.m's interface to match other library modules.
>
> library/psqueue.m:
>    Make the psqueue interface more consistent with other standard library
>    modules.
>
> tests/hard_coded/psqueue_test.exp:
> tests/hard_coded/psqueue_test.m:
>    Update tests.
> ---
> library/psqueue.m                 | 571 ++++++++++++++++++++------------------
> tests/hard_coded/psqueue_test.exp |   3 +-
> tests/hard_coded/psqueue_test.m   |  57 ++--
> 3 files changed, 327 insertions(+), 304 deletions(-)
>
> diff --git a/library/psqueue.m b/library/psqueue.m
> index 481c02d..4a490cf 100644
> --- a/library/psqueue.m
> +++ b/library/psqueue.m
> @@ -54,11 +54,21 @@
>     %
> :- pred is_empty(psqueue(P, K)::in) is semidet.
>
> +    % create singleton psqueue
> +    %
> +:- pred singleton(P::in, K::in, psqueue(P, K)::out) is det.
> +:- func singleton(P, K) = psqueue(P, K).

Is there a good reason to have a predicate verison of singleton?
It's not something we provide for most other data structures (e.g
bimaps, cord, injections, maps).

Cheers,
Julien.