arr .~ (i,j) .= arr ! (a,b) + arr ! (x,y)
main = mapM_ (putStrLn . foldMap show) [bool 0 1 . (==x) <$> [1..size]| x<-[1..size]]
x .* y = replicate y x
main = mapM_ (putStrLn . foldMap show) [0 .* x ++ 1 : 0 .* (size-x)| x<-[0..size-1]]
a .// l = mapM_ (uncurry $ writeArray a) l
pickFn f g (b,v) | b = g v | otherwise = f v
main = do
arr <- newArray ((1,1), (size,size)) 0
arr .// [((x,x),1)|x<-[1..size]]
mapM_ (pickFn putStr putStrLn . (((==size).snd) *** show)) $ getAssocs arr
sudo apt-get install haskell-stack
stack setup
stack ghci --package matrix
import Data.Matrix
print $ identity 10
Note that you can still capture any property you want via non-metaprogramming types (though you may require a trusted kernel to keep things performant) but that can be trickier to work with than a test for people who are much more accustomed to tests than types.
Also note that writing a function that should work, but won't typecheck can also reveal a flaw in the model (or in what you thought the model should be, or in what kind of operations you thought should work)