Anonymous user
Ulam spiral (for primes): Difference between revisions
Added Haskell version
(→{{header|Ruby}}: A form of improvement) |
(Added Haskell version) |
||
Line 881:
Bounding the display with framework symbols might help readability, but is not in the specification. For layout here, each line has had a space inserted at the start.
=={{header|Haskell}}==
<lang haskell>import Data.List
import Data.Numbers.Primes
-- Add a row to existing spiral by rotating right and adding new row to top
-- Results in spirals that turn in the wrong direction and must later be fixed.
addRow :: [[Int]] -> [[Int]]
addRow spiral = let height = length spiral
width = length $ head spiral
row = [height*width+1.. height*width+height]
in row : reverse (transpose spiral)
-- Generate spiral by adding two rows (vertical & horizontal) to smaller spiral
preSpiral :: Int => [[Int]]
preSpiral 1 = [[1]]
preSpiral n = addRow $ addRow $ preSpiral (n-1)
-- Make ulamSpiral; fix spiral direction by flipping preSpiral.
ulamSpiral :: Int => [[Int]]
ulamSpiral n | odd n = reverse $ preSpiral n
| otherwise = map reverse $ preSpiral n
-- Make and print ulamSpiral:
-- Use converter to change numbers to strings.
-- Change empty strings to dashes.
-- Pad strings out to correct length before printing.
prettyPrintSpiral :: Int -> (Int -> String) -> IO ()
prettyPrintSpiral n converter =
let stringSpiral = map (map converter) (ulamSpiral n)
maxLen = maximum (map (maximum.map length) stringSpiral)
dashFunc s = if s == "" then replicate maxLen '-' else s
padFunc s = replicate (maxLen - length s) ' ' ++ s
padded = map (padFunc.dashFunc)
showRow = unwords.padded
in mapM_ (putStrLn.showRow) stringSpiral
main :: IO ()
main = do
-- Display with converter that shows primes as Strings.
prettyPrintSpiral 10 (\n -> if isPrime n then show n else "")
putStrLn ""
-- Display with converter that shows primes as single dots.
prettyPrintSpiral 60 (\n -> if isPrime n then "*" else " ") </lang>
{{out}}
<pre style="font-size:80%">-- -- -- 97 -- -- -- -- -- --
-- -- -- -- 61 -- 59 -- -- --
-- 37 -- -- -- -- -- 31 -- 89
67 -- 17 -- -- -- 13 -- -- --
-- -- -- 5 -- 3 -- 29 -- --
-- -- 19 -- -- 2 11 -- 53 --
-- 41 -- 7 -- -- -- -- -- --
71 -- -- -- 23 -- -- -- -- --
-- 43 -- -- -- 47 -- -- -- 83
73 -- -- -- -- -- 79 -- -- --
* * * * * * * *
* * * * * * * * * *
* * * * * * *
* * * * * *
* * * * * * * * * * *
* * * * *
* * * * * * * *
* * * * * * * * * *
* * * * * *
* * * * * * * * * * *
* * * * * * * * *
* * * * * * *
* * * * * * * * * * * *
* * * * * *
* * * * * * *
* * * * * * *
* * * * * * * *
* * * * * *
* * * * * * * * * *
* * * * * * * * *
* * * * * * *
* * * * * * * * * *
* * * * * * * * * * * *
* * * * * * *
* * * * * * * * * *
* * * * * * * * * * * * *
* * * *
* * * * * * * * * * * * *
* * * * * * * * * * * * * * *
* * * * *
* * * * * * * * * * * * * *
* * * * * *
* * *
* * * * * * * * * * * * * * * *
* * * * * * * * * * * *
* * * *
* * * * * * * * * *
* * * * * * * *
* * * * *
* * * * * * * * * *
* * * * * * * * * * * * * *
* * * *
* * * * * * * * * * * *
* * * * * * * * * *
* * * * * * *
* * * * * * * *
* * * * * * *
* * * * * * * *
* * * * * *
* * * * * * * * * *
* * * * * * *
* * * * * * *
* * * * * * * * * *
* * * *
* * * * * * * *
* * * * * * *
* * * * * * * *
* * * * * * *
* * * * *
* * * * * * * </pre>
=={{header|J}}==
| |||