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  1. triangulate (x:a:b:xs) = scanl (\(x, a, b) n -> (x, b, n)) xs (x, a, b)
  2. main = print $ triangulate $ [1, 2, 3, 4, 5, 6, 7]
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
[1 of 1] Compiling Main             ( prog.hs, prog.o )

prog.hs:1:59:
    Couldn't match expected type `(t, b, b)'
           against inferred type `[t1]'
    In the second argument of `scanl', namely `xs'
    In the expression: scanl (\ (x, a, b) n -> (x, b, n)) xs (x, a, b)
    In the definition of `triangulate':
        triangulate (x : a : b : xs)
                      = scanl (\ (x, a, b) n -> (x, b, n)) xs (x, a, b)
stdout
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Standard output is empty
https://ideone.com/xCStw
language:
Haskell (ghc 8.4.4)
created:
14 years ago
visibility:
public

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