Created
December 21, 2011 19:08
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! A simple program that generates Excel spreadsheet column id corresponding to given column number. | |
! For example: | |
! 14 - N | |
! 26 - Z | |
! 27 - AA | |
! 29 - AC | |
USING: kernel math math.ranges sequences strings ; | |
IN: excel-columns | |
! Use the following after 'alphabet' definition to make it a compile time constant. | |
! << \ alphabet alphabet define-constant >> | |
: alphabet ( -- seq ) CHAR: A CHAR: Z [a,b] ; | |
: nth-char ( n -- char ) 25 + 26 mod alphabet nth 1string ; | |
: break-26 ( m -- n o ) 26 /mod ; | |
: column-id ( i -- str ) dup 26 <= [ nth-char ] [ break-26 [ column-id ] bi@ append ] if ; | |
: test-run ( -- ) 1000 [1,b] [ dup column-id 2array . ] each ; | |
MAIN: test-run |
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import Control.Applicative | |
import Control.Arrow | |
import Control.Monad | |
import Control.Monad.Instances | |
import qualified Data.Vector as V | |
-- Y U NO IN STANDARD LIBRARY????!!!! | |
if' :: Bool -> a -> a -> a | |
if' cond x y = if cond then x else y | |
alphabet :: Vector Char | |
alphabet = V.enumFromTo 'A' 'Z' | |
nthChar :: Int -> String | |
nthChar = (:[]) . (alphabet V.!) . (`mod` 26) . (+ 25) | |
break26 :: Int -> (Int, Int) | |
break26 = (`divMod` 26) | |
columnId :: Int -> String | |
columnId = if' <$> (<= 26) <*> nthChar <*> uncurry (++) . join (***) columnId . break26 | |
main :: IO () | |
main = forM_ [1..100] (print . (id &&& columnId)) |
@DanielOberg: Yes, I know about that tool. (It's the same thing as lambdabot's @pl, right?) I meant, can you write something that can be "read"? Sections of (.)
don't count (as I said here: http://missingfaktor.blogspot.com/2011/12/sections-of.html). I wrote the columnId
definition without any help from lambdabot, and I find it readable. The data flow is easy to visualize. Can we do something like that for break26
?
We can simplify it a bit without much effort:
(ap ((&&&) . flip div) (flip mod)) 26
@DanielOberg: That one looks cool. Thanks!
To write break26 while only using 26 once, why not write
let break26 = (`divMod` 26)
@chris-taylor: Thanks. I wasn't aware of that function. Turns out Factor has /mod
as well. Will update the snippets accordingly.
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There is a tool for it. :D