Brace expansion: Difference between revisions

Line 920:

[http://www.reddit.com/r/readablecode/comments/1w6exe/p6_crosswalk_braceexpansionparses/cf229at "Here is a direct translation to Haskell using parsec"] (of [http://rosettacode.org/mw/index.php?title=Brace_expansion&oldid=175567#Perl_6 an earlier version of the Perl 6 solution]):

<lang haskell>~~import~~ ~~Control.Applicative~~ ~~(liftA2,~~ ~~pure, (<$>), (<*>))~~

<lang haskell>{-# LANGUAGE FlexibleContexts #-}

import Control.Monad (forever)

import Text.Parsec

parser :: Parsec String u [String]

parser =

~~parser~~ = expand <$> many (try alts <|> try alt1 <|> escape <|> pure . pure <$> anyChar)

expand <$> many (try alts <|> try alt1 <|> escape <|> pure . pure <$> anyChar)

where

alts = concat <$> between (char '{') (char '}') (alt `sepBy2` char ',')

~~alt1~~ = ~~(:[]).('{':).(++"}")~~ <$> between (char '{') (char '}') (~~many~~ $ ~~noneOf~~ ",~~{}"~~)

alts = concat <$> between (char '{') (char '}') (alt `sepBy2` char ',')

alt1 =

⚫

~~alt = expand <$>~~ many (try alts <|> try alt1 <|> escape <|> pure . pure <$> noneOf ",}")

(: []) . ('{' :) . (++ "}") <$>

⚫

escape = pure <$> sequence [char '\\', anyChar]

~~expand~~ = ~~foldr~~ (~~liftA2~~ ~~(++))~~ [""]

between (char '{') (char '}') (many $ noneOf ",{}")

alt =

⚫

p `sepBy2` sep = ~~liftA2~~ (:) p (many1 (sep >> p))

expand <$>

⚫

many (try alts <|> try alt1 <|> escape <|> pure . pure <$> noneOf ",}")

⚫

escape = pure <$> sequence [char '\\', anyChar]

expand = foldr ((<*>) . fmap (++)) [""]

⚫

p `sepBy2` sep = (:) <$> p <*> many1 (sep >> p)

showExpansion :: String -> String

showExpansion =

(++) <*> (("\n-->\n" ++) . either show unlines . parse parser [])

main :: IO ()

main =

main = forever $ parse parser [] <$> getLine >>= either print (mapM_ putStrLn)</lang>

mapM_

(putStrLn . showExpansion)

⚫

[ "~/{Downloads,Pictures}/*.{jpg,gif,png}"

, "It{{em,alic}iz,erat}e{d,}, please."

, "{,{,gotta have{ ,\\, again\\, }}more }cowbell!"

⚫

, "{}} some {\\\\{edge,edgy} }{ cases, here\\\\\\\\\\}"

]</lang>

<pre>~/{Downloads,Pictures}/*.{jpg,gif,png}

<pre>$ ./bracex

-->

⚫

~/{Downloads,Pictures}/*.{jpg,gif,png}

~/Downloads/*.jpg

~/Downloads/*.gif

Line 945:

Line 961:

~/Pictures/*.gif

~/Pictures/*.png

It{{em,alic}iz,erat}e{d,}, please.

-->

Itemized, please.

Itemize, please.

Line 952:

Line 970:

Iterated, please.

Iterate, please.

{,{,gotta have{ ,\, again\, }}more }cowbell!

-->

cowbell!

more cowbell!

gotta have more cowbell!

gotta have\, again\, more cowbell!

⚫

{}} some {\\{edge,edgy} }{ cases, here\\\}

{}} some {\\edge }{ cases, here\\\}

{}} some {\\{edge,edgy} }{ cases, here\\\\\}

-->

{}} some {\\~~edgy~~ }{ cases, here\\\}

{}} some {\\edge }{ cases, here\\\\\}

a{b{1,2}c

{}} some {\\edgy }{ cases, here\\\\\}</pre>

a{b1c

a{b2c

a{1,2}b}c

a1b}c

a2b}c

a{1,{2},3}b

a1b

a{2}b

a3b

a{b{1,2}c{}}

a{b1c{}}

a{b2c{}}

^D

bracex: <stdin>: hGetLine: end of file</pre>

=={{header|Go}}==