Oh! Nice. If you have an account on SO feel free to post it, I'll vote it up past my original. If you don't, I'll replace mine with yours and link to your message on the Forum.
-Dan -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Marshall Lochbaum Sent: Monday, July 22, 2013 9:38 PM To: [email protected] Subject: Re: [Jprogramming] Code golf: approximate pi I haven't been able to shorten your code. But here's a version which handles odd numbers, at the cost of only two characters: c=:*:({&' *'@],&":2%(%+/@,))]>(|@j./~2&|#])@i:@<: Rather than filtering by position (_2{.\]), we filter the x values by oddness (2&|#]). Marshall On Mon, Jul 22, 2013 at 07:54:21PM -0400, Dan Bron wrote: > There's a code golf challenge on StackOverflow [1] which asks us to > generate an approximation of a circle in ASCII (i.e. using integral > Cartesian > coordinates) and a corresponding estimation of pi. > > For example, the 8th order circle in ASCII has 15 rows and 8 columns > and gives an approximate value of pi of 3.125. The detailed > specifications of input, output, and edge cases can be found at > http://stackoverflow.com/questions/2440314/code-golf-day/ but the > general concept is take positive integer as an input, and output the > circle with its corresponding estimate of pi. Like this: > > c 8 > ******* > ************* > *************** > *************** > *************** > *************** > ************* > ******* > 3.125 > > This is a code golf challenge. Most common programming languages can > get it down to ~100 characters. The shortest solution, outside of J, > is written in bc (the command-line calculator) and weighs in at 88 characters. > > Without too much effort, I put together a J solution of 47 characters > (a little over half the length of the previous champion)*. > > Uncompressed, the verb might look like this: > > c =: verb define > pythag =. y > | j./~ i:y-1 NB. r^2 > x^2 + y^2 > squished =. _2 {.\ pythag NB. Odd rows only > piApx =. (2 * +/ , squished) % y*y > (squished { ' *') , ": piApx > ) > > Here it is in its compressed form: > > c=:*:({&' *'@],&":2%(%+/@,))_2{.\]>|@j./~@i:@<: > > Can you pare it down at all? Perhaps using a different approach? > > Note also that there is extra credit available for a solution which > handles odd inputs (i.e. odd numbers) appropriately, which this version doesn't. > > -Dan > > * The 47 characters includes the assignment to a name, so the function > can be reused. > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
