Re: RPN calculator in Perl 6
http://sial.org/pbot/37077 A slightly improved syntax, as per jnthn++ suggestion... Em Sáb, 2009-06-06 às 18:08 +0200, Daniel Carrera escreveu: Daniel Carrera wrote Ok, try again: % perl6 rpn.pl 2 2+ 2 2 You can probably fix that with a different split() line. I tried using ws instead of \s+ but the program just hangs forever. Hmm.. it certainly is in the split, I'm not sure how to get the barrier between the 2 and the + I also tried a more complex expression, and the calculator didn't like it: % perl6 rpn.pl 5 4 + 3 / 5 3 - * Error parsing expression near * er... that's because I didn't tried to implement it... but it certainly is possible to, just by declaring the :(@a, Num $a) variant... daniel
Re: RPN calculator in Perl 6
Em Sáb, 2009-06-06 às 19:45 -0400, Minimiscience escreveu: my $ls = @a.shift; my $rs = @a.shift; To: my $rs = @a.pop; my $ls = @a.pop; Thanks... this was already solved in the latest version I sent http://sial.org/pbot/37089 daniel
Re: RPN calculator in Perl 6
On Sat, 2009-06-06 at 13:18 -0300, Daniel Ruoso wrote: http://sial.org/pbot/37077 A slightly improved syntax, as per jnthn++ suggestion... My list mail has been very delayed, so this may be out of sequence, but in case no one mentioned it yet: http://sial.org/pbot/37102 (That's ruoso++'s later 37100 paste with a couple small tweaks by me.) I wanted to shrink that even further by replacing the given/when with a direct call of the correct op variant, but I couldn't figure out how to do that in current Rakudo. (And just using eval inside a multi seemed to be broken.) -'f
Re: RPN calculator in Perl 6
Em Sáb, 2009-06-06 às 14:06 +0200, Daniel Carrera escreveu: I just wrote a blog post showing how to make a reverse polish notation calculator in Perl 6. In the process I show some of Perl 6's grammar features. TIMTOWTDI ;) http://sial.org/pbot/37075 daniel
Re: RPN calculator in Perl 6
Em Sáb, 2009-06-06 às 18:22 +0200, Daniel Carrera escreveu: Daniel Ruoso wrote: er... that's because I didn't tried to implement it... but it certainly is possible to, just by declaring the :(@a, Num $a) variant... Well, * is implemented, so I guess you are talking about complex expressions. Yes... that's what wasn't implemented... But now it is ;) http://sial.org/pbot/37085 daniel
Re: RPN calculator in Perl 6
Em Sáb, 2009-06-06 às 19:51 +0200, Daniel Carrera escreveu: Daniel Ruoso wrote: Yes... that's what wasn't implemented... But now it is ;) http://sial.org/pbot/37085 Close, but... % perl6 rpn.pl 5 4 + 3 / 5 3 - * -6 That should be a positive 6. Fixed now! http://sial.org/pbot/37088 (with a op trace included, so one can see what's happening...) Are you planning to write a post explaining how your program works? Maybe, but if you want to beat me to it, feel free ;) I figure that the explanation is as useful as the example. I sure spent a lot of time writing the blog post. I'm not sure I'll have the time to write it soon, but it will certainly be on my list, unless you kindly post about it first ;) daniel
Re: RPN calculator in Perl 6
Daniel Ruoso wrote: TIMTOWTDI ;) The objective of the blog was more about the learning + teaching experience than anything else. http://sial.org/pbot/37075 % perl rpn.pl 2 2 + Semicolon seems to be missing at rpn.pl line 2. String found where operator expected at rpn.pl line 13, near where '+' (Do you need to predeclare where?) Array found where operator expected at rpn.pl line 14, near ] (Missing operator before ?) Scalar found where operator expected at rpn.pl line 14, near @($a (Missing operator before $a?) String found where operator expected at rpn.pl line 17, near where '-' (Do you need to predeclare where?) Array found where operator expected at rpn.pl line 18, near ] (Missing operator before ?) Scalar found where operator expected at rpn.pl line 18, near @($a (Missing operator before $a?) String found where operator expected at rpn.pl line 21, near where '*' (Do you need to predeclare where?) Array found where operator expected at rpn.pl line 22, near *] (Missing operator before ?) Scalar found where operator expected at rpn.pl line 22, near @($a (Missing operator before $a?) Semicolon seems to be missing at rpn.pl line 24. String found where operator expected at rpn.pl line 25, near where '/' (Do you need to predeclare where?) Semicolon seems to be missing at rpn.pl line 28. String found where operator expected at rpn.pl line 30, near fail 'Error parsing expression near ' (Do you need to predeclare fail?) Array found where operator expected at rpn.pl line 33, near ] (Missing operator before ?) Bareword found where operator expected at rpn.pl line 33, near @*ARGS (Missing operator before ARGS?) Operator or semicolon missing before *ARGS at rpn.pl line 33. Ambiguous use of * resolved as operator * at rpn.pl line 33. syntax error at rpn.pl line 1, near \. Missing right curly or square bracket at rpn.pl line 34, at end of line Execution of rpn.pl aborted due to compilation errors.
Re: RPN calculator in Perl 6
Daniel Carrera wrote: http://sial.org/pbot/37075 % perl rpn.pl 2 2 + Tee hee... that should have been perl6. :-) Ok, try again: % perl6 rpn.pl 2 2+ 2 2
Re: RPN calculator in Perl 6
[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
