any(@originals) ~~ { .foo eq $bar} (was Re: renaming "grep" to "where")

[Markus Laire]

On 9/19/06, Trey Harris <tr...@lopsa.org> wrote:
> In a message dated Mon, 18 Sep 2006, Darren Duncan writes:
> > @filtered = @originals.where:{ .foo eq $bar };
>
> Note that this can be written:
>
> @filtered = any(@originals) ~~ { .foo eq $bar};

This doesn't seem to be correct.

According to S03 junctions "thread through operations, returning
another junction representing the result". Instead of returning the
filtered values, this seems to allways return one of
any(Bool::False) # If all comparisons were false
any(Bool::True) # If all comparisons were true
any(Bool::False, Bool::True) # If some comparisons were false and some true

Testing a concrete example in pugs (r13034):
pugs> my @a = (1..10);
(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
pugs> any(@a) ~~ { $_ < 0 }
(Bool::False)
pugs> any(@a) ~~ { $_ > 0 }
(Bool::True)
pugs> any(@a) ~~ { $_ % 2 }
(Bool::False | Bool::True)

--
Markus Laire

[Trey Harris]

In a message dated Tue, 19 Sep 2006, Markus Laire writes:

> On 9/19/06, Trey Harris <tr...@lopsa.org> wrote:
>> In a message dated Mon, 18 Sep 2006, Darren Duncan writes:
>> > @filtered = @originals.where:{ .foo eq $bar };
>>
>> Note that this can be written:
>>
>> @filtered = any(@originals) ~~ { .foo eq $bar};
>
> This doesn't seem to be correct.

See S09. "In particular,

@result = any(@x) ~~ {...};

is equivalent to

@result = grep {...}, @x;"

> Testing a concrete example in pugs (r13034):
> pugs> my @a = (1..10);
> (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
> pugs> any(@a) ~~ { $_ < 0 }
> (Bool::False)
> pugs> any(@a) ~~ { $_ > 0 }
> (Bool::True)
> pugs> any(@a) ~~ { $_ % 2 }
> (Bool::False | Bool::True)

This feature is unimplemented.

Trey