[Haskell-cafe] Using ShowS or Difference Lists
holgersiegel74 at yahoo.de
Sat Feb 6 08:14:37 EST 2010
Am Samstag, den 06.02.2010, 23:12 +1030 schrieb Mark Spezzano:
> Just wondering whether I can use ShowS or tupling or Difference Lists to speed up the following code?
> It's basic text processing. It takes in a list of Lines where each Line
> is a list of Words and intersperses " " between them then concatenates
> them into a longer String. Note that there is a recursive call and the
> ++ operator.
> -- Function: joinLines
> -- Joins the Words within Lines together with whitespace and newline characters
> -- Argument: Lines to pad with whitespace and newlines
> -- Evaluate: The processed and concatenated String
> joinLines :: [Line] -> String
> joinLines (l:) = concat (intersperse " " l)
> joinLines (l:ls) = (concat (intersperse " " l)) ++ ('\n':joinLines ls)
You should use the existing library functions and leave the
optimisations to their implementor:
joinLines :: [[String]] -> String
joinLines = intercalate "\n" . map (intercalate " ")
Now you can easily switch to the faster ByteString library by simply
changing the import statement.
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