:: a -> [a] -> [a]

The intersperse function takes an element and a list and `intersperses' that element between the elements of the list.

Laziness

intersperse has the following properties

>>> take 1 (intersperse undefined ('a' : undefined))
"a"

>>> take 2 (intersperse ',' ('a' : undefined))
"a*** Exception: Prelude.undefined

Examples

>>> intersperse ',' "abcde"
"a,b,c,d,e"

>>> intersperse 1 [3, 4, 5]
[3,1,4,1,5]

Append an element to the start of a list, an alias for (:).

cons 't' "est" == "test"
\x xs -> uncons (cons x xs) == Just (x,xs)

The intersperse function takes an element and a list and `intersperses' that element between the elements of the list. For example,

>>> intersperse ',' "abcde"
"a,b,c,d,e"

init of non-empty list, safe. O(n). init1 a as = init (a:as)

Used to make switching to the text package easier.

O(n) Prepend an element

Replace all locations in the input with the same value. The default definition is fmap . const, but this may be overridden with a more efficient version.

Examples

Perform a computation with Maybe and replace the result with a constant value if it is Just:

>>> 'a' <$ Just 2
Just 'a'

>>> 'a' <$ Nothing
Nothing

Replace all locations in the input with the same value. The default definition is fmap . const, but this may be overridden with a more efficient version. Using ApplicativeDo: 'a <$ bs' can be understood as the do expression

do bs
pure a

with an inferred Functor constraint.

Replace all locations in the input with the same value. The default definition is fmap . const, but this may be overridden with a more efficient version.

delete x removes the first occurrence of x from its list argument. It is a special case of deleteBy, which allows the programmer to supply their own equality test.

Examples

>>> delete 'a' "banana"
"bnana"

>>> delete "not" ["haskell", "is", "not", "awesome"]
["haskell","is","awesome"]

Cons an element on to the front of a list unless it is already there.

delete x removes the first occurrence of x from its list argument. For example,

>>> delete 'a' "banana"
"bnana"

It is a special case of deleteBy, which allows the programmer to supply their own equality test.