:: [a] -> a -> Int

elemIndexJust :: (Partial, Eq a) => a -> [a] -> Int
safe Safe, hledger Hledger.Cli.Script, yesod-paginator Yesod.Paginator.Prelude
elemIndexJust op = fromJust . elemIndex op
countElem :: Eq a => a -> [a] -> Int
MissingH Data.List.Utils
Returns a count of the number of times the given element occured in the given list.
alwaysElemRIndex :: Eq a => a -> [a] -> Int
MissingH Data.List.Utils
Like elemRIndex, but returns -1 if there is nothing found.
count :: Eq a => a -> [a] -> Int
speculate Test.Speculate.Utils
findIdx :: Eq a => [a] -> a -> Maybe Int
Agda Agda.TypeChecking.MetaVars
Find position of a value in a list. Used to change metavar argument indices during assignment. reverse is necessary because we are directly abstracting over the list.
elemIndex :: Eq a => a -> [a] -> Maybe Int
base Data.List, ghc-internal GHC.Internal.Data.List GHC.Internal.Data.OldList, xmonad-contrib XMonad.Prelude
The elemIndex function returns the index of the first element in the given list which is equal (by ==) to the query element, or Nothing if there is no such element. For the result to be Nothing, the list must be finite.

Examples

>>> elemIndex 4 [0..]
Just 4

>>> elemIndex 'o' "haskell"
Nothing

>>> elemIndex 0 [1..]
* hangs forever *
elemRIndex :: Eq a => a -> [a] -> Maybe Int
MissingH Data.List.Utils
Returns the rightmost index of the given element in the given list.
elemIndex :: Eq a => a -> [a] -> Maybe Int
rio RIO.List, base-prelude BasePrelude
The elemIndex function returns the index of the first element in the given list which is equal (by ==) to the query element, or Nothing if there is no such element. 
>>> elemIndex 4 [0..]
Just 4
elemIndex :: Eq a => a -> [a] -> Maybe Int
prelude-compat Data.List2010
elemIndex :: Eq a => a -> [a] -> Maybe Int
rebase Rebase.Prelude, hledger Hledger.Cli.Script, LambdaHack Game.LambdaHack.Core.Prelude
The elemIndex function returns the index of the first element in the given list which is equal (by ==) to the query element, or Nothing if there is no such element. For the result to be Nothing, the list must be finite. 
>>> elemIndex 4 [0..]
Just 4
elemIndex :: (C n, Eq a) => a -> [a] -> Maybe n
numeric-prelude NumericPrelude.List.Generic
genericElemIndex :: (Eq a, Integral i) => a -> [a] -> Maybe i
Agda Agda.Utils.List
A generalised variant of elemIndex. O(n).
elemIndex :: (Vector v a, Eq a) => a -> v a -> Maybe Int
rio RIO.Vector
O(n) Yield Just the index of the first occurence of the given element or Nothing if the vector does not contain the element. This is a specialised version of findIndex.