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  1. Infix :: Fixity

    ghc-internal GHC.Internal.Data.Data

    No documentation available.

  2. Prefix :: Fixity

    ghc-internal GHC.Internal.Data.Data

    No documentation available.

  3. constrFixity :: Constr -> Fixity

    ghc-internal GHC.Internal.Data.Data

    Gets the fixity of a constructor

  4. fix :: (a -> a) -> a

    ghc-internal GHC.Internal.Data.Function

    fix f is the least fixed point of the function f, i.e. the least defined x such that f x = x. When f is strict, this means that because, by the definition of strictness, f ⊥ = ⊥ and such the least defined fixed point of any strict function is ⊥.

    Examples

    We can write the factorial function using direct recursion as 
    >>> let fac n = if n <= 1 then 1 else n * fac (n-1) in fac 5
120
    This uses the fact that Haskell’s let introduces recursive bindings. We can rewrite this definition using fix, Instead of making a recursive call, we introduce a dummy parameter rec; when used within fix, this parameter then refers to fix’s argument, hence the recursion is reintroduced. 
    >>> fix (\rec n -> if n <= 1 then 1 else n * rec (n-1)) 5
120
    Using fix, we can implement versions of repeat as fix . (:) and cycle as fix . (++) 
    >>> take 10 $ fix (0:)
[0,0,0,0,0,0,0,0,0,0]

    >>> map (fix (\rec n -> if n < 2 then n else rec (n - 1) + rec (n - 2))) [1..10]
[1,1,2,3,5,8,13,21,34,55]

    Implementation Details

    The current implementation of fix uses structural sharing 
    fix f = let x = f x in x
    A more straightforward but non-sharing version would look like 
    fix f = f (fix f)

  5. isInfixOf :: Eq a => [a] -> [a] -> Bool

    ghc-internal GHC.Internal.Data.List

    The isInfixOf function takes two lists and returns True iff the first list is contained, wholly and intact, anywhere within the second.

    Examples

    >>> isInfixOf "Haskell" "I really like Haskell."
True

    >>> isInfixOf "Ial" "I really like Haskell."
False
    For the result to be True, the first list must be finite; for the result to be False, the second list must be finite: 
    >>> [20..50] `isInfixOf` [0..]
True

    >>> [0..] `isInfixOf` [20..50]
False

    >>> [0..] `isInfixOf` [0..]
* Hangs forever *

  6. isPrefixOf :: Eq a => [a] -> [a] -> Bool

    ghc-internal GHC.Internal.Data.List

    The isPrefixOf function takes two lists and returns True iff the first list is a prefix of the second.

    Examples

    >>> "Hello" `isPrefixOf` "Hello World!"
True

    >>> "Hello" `isPrefixOf` "Wello Horld!"
False
    For the result to be True, the first list must be finite; False, however, results from any mismatch: 
    >>> [0..] `isPrefixOf` [1..]
False

    >>> [0..] `isPrefixOf` [0..99]
False

    >>> [0..99] `isPrefixOf` [0..]
True

    >>> [0..] `isPrefixOf` [0..]
* Hangs forever *
    isPrefixOf shortcuts when the first argument is empty: 
    >>> isPrefixOf [] undefined
True

  7. isSuffixOf :: Eq a => [a] -> [a] -> Bool

    ghc-internal GHC.Internal.Data.List

    The isSuffixOf function takes two lists and returns True iff the first list is a suffix of the second.

    Examples

    >>> "ld!" `isSuffixOf` "Hello World!"
True

    >>> "World" `isSuffixOf` "Hello World!"
False
    The second list must be finite; however the first list may be infinite: 
    >>> [0..] `isSuffixOf` [0..99]
False

    >>> [0..99] `isSuffixOf` [0..]
* Hangs forever *

  8. stripPrefix :: Eq a => [a] -> [a] -> Maybe [a]

    ghc-internal GHC.Internal.Data.List

    The stripPrefix function drops the given prefix from a list. It returns Nothing if the list did not start with the prefix given, or Just the list after the prefix, if it does.

    Examples
    >>> stripPrefix "foo" "foobar"
Just "bar"

    >>> stripPrefix "foo" "foo"
Just ""

    >>> stripPrefix "foo" "barfoo"
Nothing

    >>> stripPrefix "foo" "barfoobaz"
Nothing

  9. isInfixOf :: Eq a => [a] -> [a] -> Bool

    ghc-internal GHC.Internal.Data.OldList

    The isInfixOf function takes two lists and returns True iff the first list is contained, wholly and intact, anywhere within the second.

    Examples

    >>> isInfixOf "Haskell" "I really like Haskell."
True

    >>> isInfixOf "Ial" "I really like Haskell."
False
    For the result to be True, the first list must be finite; for the result to be False, the second list must be finite: 
    >>> [20..50] `isInfixOf` [0..]
True

    >>> [0..] `isInfixOf` [20..50]
False

    >>> [0..] `isInfixOf` [0..]
* Hangs forever *

  10. isPrefixOf :: Eq a => [a] -> [a] -> Bool

    ghc-internal GHC.Internal.Data.OldList

    The isPrefixOf function takes two lists and returns True iff the first list is a prefix of the second.

    Examples

    >>> "Hello" `isPrefixOf` "Hello World!"
True

    >>> "Hello" `isPrefixOf` "Wello Horld!"
False
    For the result to be True, the first list must be finite; False, however, results from any mismatch: 
    >>> [0..] `isPrefixOf` [1..]
False

    >>> [0..] `isPrefixOf` [0..99]
False

    >>> [0..99] `isPrefixOf` [0..]
True

    >>> [0..] `isPrefixOf` [0..]
* Hangs forever *
    isPrefixOf shortcuts when the first argument is empty: 
    >>> isPrefixOf [] undefined
True

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