Difference between revisions of "SCL Examples"
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| Line 11: | Line 11: | ||
lq = [l!i - (m-i) | i <- [0..m-1]] | lq = [l!i - (m-i) | i <- [0..m-1]] | ||
uq = [l!i + (m-i) | i <- [0..m-1]] | uq = [l!i + (m-i) | i <- [0..m-1]] | ||
| − | > expandSolution l = | + | > expandSolution l = do |
x <- possibleNextPositions l | x <- possibleNextPositions l | ||
return (l + [x]) | return (l + [x]) | ||
| Line 21: | Line 21: | ||
> repeatString k (s :: String) = sum [s | x <- [1..k]] | > repeatString k (s :: String) = sum [s | x <- [1..k]] | ||
> rowText k = repeatString k "." + "X" + repeatString (n-k-1) "." | > rowText k = repeatString k "." + "X" + repeatString (n-k-1) "." | ||
| − | > printSolution (l :: [Integer]) = | + | > printSolution (l :: [Integer]) = do |
printString (repeatString n "-") | printString (repeatString n "-") | ||
mapM (printString . rowText) l | mapM (printString . rowText) l | ||
> mapM printSolution solutions | > mapM printSolution solutions | ||
</pre> | </pre> | ||
Latest revision as of 14:34, 22 August 2012
Eight queens puzzle
Copy the following commands to the SCL console:
> n = 8
> allPositions = [0..n-1]
> possibleNextPositions l = allPositions \\ (l + lq + uq)
where
m = length l
lq = [l!i - (m-i) | i <- [0..m-1]]
uq = [l!i + (m-i) | i <- [0..m-1]]
> expandSolution l = do
x <- possibleNextPositions l
return (l + [x])
> solve k cur = if k == n
then return cur
else expandSolution cur >>= solve (k+1)
> solutions = solve 0 []
> length solutions
> repeatString k (s :: String) = sum [s | x <- [1..k]]
> rowText k = repeatString k "." + "X" + repeatString (n-k-1) "."
> printSolution (l :: [Integer]) = do
printString (repeatString n "-")
mapM (printString . rowText) l
> mapM printSolution solutions
