Beefy Boxes and Bandwidth Generously Provided by pair Networks
good chemistry is complicated,
and a little bit messy -LW
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
If you want to understand the math, I fully agree with your use of the formula. Furthermore for more complex combinatorial problems, understand how to get those formulas is extremely important.

That said, tye is right as well. While in theory that calculation gets the right answer, in practice it starts to be inaccurate for fairly small numbers. You can get around this by using a big integer package. (Or a language that understands integers of arbitrary size.) But that will be somewhat slow.

If you want to understand this, go with the formula. If you want to calculate it, go with the tricks. If you want to calculate answers to arbitrary problems, be prepared to manipulate big integers and hope that performance doesn't matter.

And if you want an even better example some day, bug me about why you should always use row-reduction to find the inverses of matrices rather than Cramer's formula. (Hint: Think numerically unstable and exponential running time, vs n**3 and much better behaved.)


In reply to In theory, theory and practice are the same... by tilly
in thread Binomial Expansion by crazyinsomniac

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others exploiting the Monastery: (3)
    As of 2014-09-20 05:05 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      How do you remember the number of days in each month?











      Results (153 votes), past polls