map a function over a NonEmpty stream

scanl is similar to foldl, but returns a stream of successive reduced values from the left:

 scanl f z [x1, x2, ...] == z :| [z `f` x1, (z `f` x1) `f` x2, ...]

Note that

 last (scanl f z xs) == foldl f z xs.

scanr is the right-to-left dual of scanl. Note that

 head (scanr f z xs) == foldr f z xs.

scanl1 is a variant of scanl that has no starting value argument:

 scanl1 f [x1, x2, ...] == x1 :| [x1 `f` x2, x1 `f` (x2 `f` x3), ...]

scanr1 is a variant of scanr that has no starting value argument.

Extract the first element of the stream

Extract the possibly empty tail of the stream

Extract the last element of the stream

Extract everything except the last element of the stream

cons onto a stream

Sort a stream

reverse a finite NonEmpty

The inits function takes a stream xs and returns all the finite prefixes of xs.

The tails function takes a stream xs and returns all the suffixes of xs.

iterate f x produces the infinite sequence of repeated applications of f to x.

 iterate f x = [x, f x, f (f x), ..]

repeat x returns a constant stream, where all elements are equal to x.

cycle xs returns the infinite repetition of xs:

 cycle [1,2,3] = 1 :| [2,3,1,2,3,...]

insert an item into a NonEmpty

take n xs returns the first n elements of xs.

Beware: passing a negative integer as the first argument will cause an error.

drop n xs drops the first n elements off the front of the sequence xs.

Beware: passing a negative integer as the first argument will cause an error.

splitAt n xs returns a pair consisting of the prefix of xs of length n and the remaining stream immediately following this prefix.

Beware: passing a negative integer as the first argument will cause an error.

takeWhile p xs returns the longest prefix of the stream xs for which the predicate p holds.

dropWhile p xs returns the suffix remaining after takeWhile p xs.

span p xs returns the longest prefix of xs that satisfies p, together with the remainder of the stream.

The break p function is equivalent to span not . p.

filter p xs, removes any elements from xs that do not satisfy p.

The partition function takes a predicate p and a stream xs, and returns a pair of streams. The first stream corresponds to the elements of xs for which p holds; the second stream corresponds to the elements of xs for which p does not hold.

The group function takes a stream and returns a stream of lists such that flattening the resulting stream is equal to the argument. Moreover, each sublist in the resulting stream contains only equal elements. For example,

 group $ cycle "Mississippi" = "M" : "i" : "ss" : "i" : "ss" : "i" : "pp" : "i" : "M" : "i" : ...

The isPrefix function returns True if the first argument is a prefix of the second.

xs !! n returns the element of the stream xs at index n. Note that the head of the stream has index 0.

Beware: passing a negative integer as the first argument will cause an error.

The zip function takes two streams and returns a list of corresponding pairs.

The zipWith function generalizes zip. Rather than tupling the functions, the elements are combined using the function passed as the first argument to zipWith.

The unzip function is the inverse of the zip function.

The words function breaks a stream of characters into a stream of words, which were delimited by white space.

The unwords function is an inverse operation to words. It joins words with separating spaces.

The lines function breaks a stream of characters into a list of strings at newline characters. The resulting strings do not contain newlines.

The unlines function is an inverse operation to lines. It joins lines, after appending a terminating newline to each.

Converts an non-empty list to a stream.

Convert a stream to a list efficiently