Hi "Z", On Sunday 24 Apr 2011 15:08:18 z sway wrote: > the expression only contains number and"+*()" > the form of list is like[op,node1,node2...],op is "+"or"*",node can be a > number or a child list. > e.g :1*2+3*4*(5+6) > [ '+', ['*', '1', '2'], ['*', '3', '4', ['+','5', '6'] ] ] > Thanks!
Well, I think I understand your question. If you: 1. Want to parse the statements look at the various parser generators on CPAN: http://perl-begin.org/uses/text-parsing/#parser-generators This seems what you want. Using them requires some knowledge in the underlying theory of the so-called "formal languages" and "context-free grammars" (whose study has a lot of discrete mathematics formalism, but is conceptually very simple), and parsers generators tend to be very "subtle and quick to become angry" beasts - i.e: they are hard to get right and often expose implementation details. 2. If you want to generate a serial expression from a tree, then this can be easily done sub-optimally using recursion, but will require more logic to do properly (i,e: while omitting unnecessary parentheses).. See: http://en.wikipedia.org/wiki/Computer_algebra_system Implementing a full user-friendly system like that is probably out-of-scope for what you want, and serious, proprietary, mathematical software (e.g: Mathematica, Matlab, Maple, etc.) can cost you a lot of money (unless you are a student). -------------- Hope that helps, because your message was a bit vague. My mind reading device is on repair, not to mention that it is limited to a 10 kilometer radius beyond which I am unable to read people's mind clearly enough, due to natural technological limitations. ;-) (Old joke - ignore.). Regards, Shlomi Fish -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ First stop for Perl beginners - http://perl-begin.org/ I hope that you agree with me that 99.9218485921% of the users wouldn't bother themselves with recompilation (or any other manual step for that matter) to make their games run 1.27127529900685765% faster ;-) -- Nadav Har'El Please reply to list if it's a mailing list post - http://shlom.in/reply . -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
