[m-rev.] diff: more code cleanups for integer.m

[Julien Fischer]

On Mon, 22 Dec 2003, Fergus Henderson wrote:

> On 22-Dec-2003, Julien Fischer <juliensf at students.cs.mu.OZ.AU> wrote:
> >
...

>
> There were some additional changes not mentioned in this log message.
> One was to convert quite a few if-then-elses from the "... -> ... ; ..." form
> to the "if .. then ... else ..." form.  Another was to change
>
> 	foo(...) -->
> 		[].
>
> to
>
> 	foo(...) --> [].
>
> in several places.
>
> That's OK this time... but in future, if you're going to make changes
> like that, it's much better to first put some sort of explicit policy
> about it in the Mercury coding guidelines.  Otherwise there is a danger
> of continual churn, as each developer rewrites things in his/her favourite
> syntax!
>
Fair enough.


> > +quot_rem(U, V, Quot, Rem) :-
> > +	( U = i(_, [UI]), V = i(_, [VI]) ->
> > +		Quot = shortint_to_integer(UI // VI),
> > +		Rem  = shortint_to_integer(UI rem VI)
> > +	;
> > +		V0 = head(V),
> > +		( V0 < basediv2 ->
> > +			M = base div (V0 + 1),
> > +				quot_rem_2(integer__zero,
> > +					mul_by_digit(M, U),
> > +					mul_by_digit(M, V), QuotZeros, R),
> > +			Rem = div_by_digit(M, R)
>
> The call to quot_rem_2 here is incorrectly intended.
>
Fixed.

> >  :- func string_to_integer_acc(list(char), integer) = integer.
> >  :- mode string_to_integer_acc(in, in) = out is semidet.
> >
> >  string_to_integer_acc([], Acc) = Acc.
> >  string_to_integer_acc([C | Cs], Acc) = Result :-
> > -    (char__is_digit(C) ->
> > -	char__to_int(C, D1),
> > -	char__to_int('0', Z),
> > -	Dig = pos_int_to_digits(D1 - Z),
> > -	NewAcc = pos_plus(Dig, mul_by_digit(10, Acc)),
> > -	Result = string_to_integer_acc(Cs, NewAcc)
> > -    ;
> > -	fail
> > -    ).
> > +	char__is_digit(C),
> > +	Digit0 = char__to_int(C),
> > +	Z = char__to_int('0'),
> > +	Digit = pos_int_to_digits(Digit0 - Z),
> > +	NewAcc = pos_plus(Digit, mul_by_digit(10, Acc)),
> > +	Result = string_to_integer_acc(Cs, NewAcc).
>
> The if-then-else here is not unnecessary.  It acts as sequential conjunction,
> and it is needed to guarantee termination with --reorder-conj,
> so it should not be removed.  Without it, the value of `Digit0 - Z'
> might be negative, and the call to pos_int_to_digits might not terminate.
>
> So please restore the if-then-else, and add a comment explaining why it is
> needed.
>
Done.

Julien.
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