[I just realized I sent this directly to Daniel rather than to the
list, so for the benefit of onlookers...]
On Jun 6, 2009, at 1:51 PM, Daniel Carrera wrote:
Daniel Ruoso wrote:
Yes... that's what wasn't implemented... But now it is ;)
http://sial.org/pbot/37085
Close, but...
% perl6 rpn.pl "5 4 + 3 / 5 3 - *"
-6
That should be a positive 6.
I think I see the problem (assuming it hasn't already been pointed out
off-list). The infix:<rpn>(@a, $op where ...) operators call .shift
on the arrays to get the operands, yet the infix:<rpn>(... , $b where /
<Num>/) operators place the numbers on the *end* of the stack, where
the next reverse-polish operator should read them from. Thus, when
the '-' is processed, the stack is "3 5 3", where the first three is
the result of "5 4 + 3 /", and the first two numbers are shifted off
for subtraction rather than the last two. In order to fix this,
either change the first two infix:<rpn>() functions so that they place
new numbers at the *beginning* of the array, or else change each
occurrence of
my $ls = @a.shift;
my $rs = @a.shift;
To:
my $rs = @a.pop;
my $ls = @a.pop;
(Note that, in addition to the use of .pop, $rs is now acquired before
$ls.)
At least, I think that's how it works.
-- Minimiscience
