Haskell - 1493 bytes
In this version, there are no detailed error messages and the output is much more basic. The major change was replacing Either String a with Maybe a and since they are both monads, this was acheived by simply swapping Right a with Just a and Left String with Nothing.
{-# LANGUAGE OverloadedStrings #-}
import Prelude hiding ((>>=),concatMap,filter,foldl,head,last,map,null,replicate)
import Control.Applicative hiding (empty)
import Control.Monad hiding (replicateM)
import Data.Vector hiding ((++),concat,foldM,reverse,zip)
main=getLine>>= \s->h$t<$>(zip$cycle[w,v])<$>b s>>= \m->u(\b(c,x)->case d b x c of r@(Just _)->r;Nothing->if not$null$findIndices(\y->e$d b y c)$t[(x,y)|x<-[0..7],y<-[0..7]];then é;else d b x$not c)k$n m
where b(x:y:s)=(:)(read [x],read [y])<$>b s;b(_:_)=é;b[]=è[];d b z c=let d=join$m(f b z c)$m(\v->(head v,last v))$replicateM 2$t[-1,0,1];in if null d;then Nothing;else u(\b (x,y)->case b!?y of Just r->(case r!?x of Just _->è$b//[(y,r//[(x,è c)])];Nothing->é);Nothing->é)b$n$d`snoc`z;e(Nothing)=w;e(Just _)=v;f b(x,y)c z@(u,v)=let r=x+u;s=y+v;t=(r,s);in (case g b t of Just(Just d)->if d==c;then l;else (case g b (r+u,s+v) of Just(Just _)->t`cons`f b t c z;_->l);Just(Nothing)->l;Nothing->l);g b(x,y)=(case b!?y of Just col->col!?x;Nothing->é);h(Just b)=p$(o$n$m(\r->o(n$m(\c->case c of Just False->"B";Just True->"W";Nothing->".")r)++"\n")b)++i(q(\(w,b)(rw,rb)->(w+rw,b+rb))(0,0)$m(\r->q(\s@(w,b)c->case c of Just True->(w+1,b);Just False->(w,b+1);_->s)(0,0)r)b);h Nothing=p"e";i(w,b)|w>b="W"++s w|b>w="B"++s b|v="N"++s(w+b);j=r 8 é;k=r 8 j//[(3,j//[(3,è v),(4,è w)]),(4,j//[(3,è w),(4,è v)])];l=empty;m=map;n=toList;o=concat;p=putStrLn;q=foldl;r=replicate;s=show;t=fromList;u=foldM;v=True;w=False;é=Nothing;è=Just
$ printf "232425140504032627" | ./nano-rve
........
........
........
B.BBB...
BBBWW...
B.B.....
..B.....
..B.....
B11
Original version - 4533 bytes
I will golf when there will be competition!
edit It has arrived
{-# LANGUAGE OverloadedStrings #-}
import Prelude hiding ((>>=),concatMap,filter,foldl,map,null,replicate)
import Control.Applicative hiding (empty)
import Control.Monad
import Data.Either
import Data.Vector hiding ((++),concat,foldM,reverse,zip)
type Case = Maybe Bool
type Board = Vector (Vector Case)
type Coord = (Int,Int)
-- fmap (toList) $ replicateM 2 [-1,0,1] -- minus (0,0)
directions :: Vector Coord
directions = fromList [(-1,-1),(-1,0),(-1,1),(0,-1),(0,1),(1,-1),(1,0),(1,1)]
-- [(x,y) | x <- [0..7], y <- [0..7]]
allCoords :: Vector Coord
allCoords = fromList [(0,0),(0,1),(0,2),(0,3),(0,4),(0,5),(0,6),(0,7),(1,0),(1,1),(1,2),(1,3),(1,4),(1,5),(1,6),(1,7),(2,0),(2,1),(2,2),(2,3),(2,4),(2,5),(2,6),(2,7),(3,0),(3,1),(3,2),(3,3),(3,4),(3,5),(3,6),(3,7),(4,0),(4,1),(4,2),(4,3),(4,4),(4,5),(4,6),(4,7),(5,0),(5,1),(5,2),(5,3),(5,4),(5,5),(5,6),(5,7),(6,0),(6,1),(6,2),(6,3),(6,4),(6,5),(6,6),(6,7),(7,0),(7,1),(7,2),(7,3),(7,4),(7,5),(7,6),(7,7)]
initBoard :: Board
initBoard = vs // [(3,v1),(4,v2)]
where va = replicate 8 Nothing
v1 = va // [(3,Just True),(4,Just False)]
v2 = va // [(3,Just False),(4,Just True)]
vs = replicate 8 va
showBoard :: Board -> String
showBoard b = (concat $ toList $ map (showRow) b) ++ (showScore b)
where showCase :: Case -> String
showCase c = case c of
Just False -> "░B"
Just True -> "▓W"
Nothing -> "██"
showRow :: Vector Case -> String
showRow r = concat (toList $ map (showCase) r) ++ "\n"
showScore :: Board -> String
showScore b = winner score ++ "\n"
where scoreCase :: (Int,Int) -> (Maybe Bool) -> (Int,Int)
scoreCase (w,b) (Just True) = (w+1,b)
scoreCase (w,b) (Just False) = (w,b+1)
scoreCase s _ = s
scoreRow :: Vector Case -> (Int,Int)
scoreRow r = foldl (scoreCase) (0,0) r
score :: (Int,Int)
score = foldl (\(w,b) (rw,rb) -> (w+rw,b+rb)) (0,0) $ map (scoreRow) b
winner :: (Int,Int) -> String
winner (w,b) | w > b = "White with " ++ show w ++ " against Black with " ++ show b ++ "."
| b > w = "Black with " ++ show b ++ " against White with " ++ show w ++ "."
| otherwise = "Nobody with " ++ show (w+b) ++ "."
printBoard :: Board -> IO ()
printBoard b = putStrLn $ showBoard b
pm :: Either String Board -> IO ()
pm (Right b) = printBoard b
pm (Left s) = putStrLn s
lookupBoard :: Board -> Coord -> Either String Case
lookupBoard b (x,y) = case b !? y of
Just col -> case col !? x of
Just c -> Right c
Nothing -> Left "x is out of bounds"
Nothing -> Left "y is out of bounds"
updateBoard :: Board -> Coord -> Bool -> Either String Board
updateBoard b (x,y) c = case b !? y of
Just r -> case r !? x of
Just _ -> Right $ b // [(y,r // [(x,Just c)])]
Nothing -> Left "x is out of bounds"
Nothing -> Left "y is out of bounds"
makePath :: Board -> Coord -> Bool -> Coord -> Vector Coord
makePath b (x,y) c (px,py) = case lookupBoard b (nx,ny) of
Right (Just pc) -> if pc == c
then empty
else case lookupBoard b (nx+px,ny+py) of
Right (Just _) -> (nx,ny) `cons` makePath b (nx,ny) c (px,py)
_ -> empty
Right (Nothing) -> empty
Left _ -> empty
where nx = x+px
ny = y+py
makeMove :: Board -> Coord -> Bool -> Either String Board
makeMove b xy@(x,y) c = if null cases
then Left $ "impossible move " ++ show xy ++ "."
else foldM (\ob (cx,cy) -> updateBoard ob (cx,cy) c) b $ toList $ cases `snoc` (x,y)
where cases = join $ map (makePath b (x,y) c) directions
makeMoves :: Board -> Vector (Bool,Coord) -> Either String Board
makeMoves b ms = foldM (\ob (c,xy) -> case makeMove ob xy c of
rb@(Right _) -> rb
Left _ -> if not $ null $ findIndices (\xy -> isRight $ makeMove ob xy c) allCoords
then Left $ "wrong move " ++ show xy ++ "."
else makeMove ob xy (not c)) b $ toList ms
movesFromString :: String -> Either String (Vector (Bool,Coord))
movesFromString cs = fromList <$> (zip $ cycle [False,True]) <$> coords cs
where coords (x:y:cs) = (:) (read [x],read [y]) <$> coords cs
coords (_:cs) = Left "invalid coordinates string"
coords [] = Right []
isRight :: Either a b -> Bool
isRight (Left _) = False
isRight (Right _) = True
main=getLine>>= \s->pm$movesFromString s>>=makeMoves initBoard
Note : Your second example should be 232425140504032627.
Tests
With screenshots to prevent eye burns.
$ printf "232425140504032627" | ./rve
$ printf "2324" | ./rve
$ printf "1" | ./rve
invalid coordinates string
$ printf "24" | ./rve
wrong move (2,4).
Is is possible to get impossible move (x,y) when you use innardics (functions from the innards of the program and that you should not use) and x/y is out of bounds.
How can you tell from what point the piece moved? in your first example there is only 1 possibility, but is it safe to assume there is always 1 possibility? – Teun Pronk – 2014-03-03T15:31:10.460
I'm sorry I don't understand the question – durron597 – 2014-03-03T15:34:08.533
3@TeunPronk in reversi no piece is moved. Each player takes turn adding pieces to the board. I assume that should answer your question. – shiona – 2014-03-03T18:42:00.807
How are we supposed to interpret more than one pair of numbers? – golfer9338 – 2014-04-17T20:21:53.773
If an illegal move is entered, must we display the state of the field at the last valid move, or is it enough to just display an error message? – marinus – 2014-06-07T18:21:19.647