Why is there a space before * in ' *'? Thanks, -----Original Message----- From: "Dan Bron" <[email protected]> Sent: 7/22/2013 7:54 PM To: "'J Programming'" <[email protected]> Subject: [Jprogramming] Code golf: approximate pi
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
