count

Returns the number of items in the collection. (count nil) returns 0. Also works on strings, arrays, and Java Collect...

empty

Returns an empty collection of the same category as coll, or nil

find

Returns the map entry for key, or nil if key not present.

first

Returns the first item in the collection. Calls seq on its argument. If coll is nil, returns nil.

get

Returns the value mapped to key, not-found or nil if key not present in associative collection, set, string, array, or...

get-in

Returns the value in a nested associative structure, where ks is a sequence of keys. Returns nil if the key is not p...

key

Returns the key of the map entry.

keys

Returns a sequence of the map's keys, in the same order as (seq map).

last

Return the last item in coll, in linear time

next

Returns a seq of the items after the first. Calls seq on its argument. If there are no more items, returns nil.

nth

Returns the value at the index. get returns nil if index out of bounds, nth throws an exception unless not-found is su...

peek

For a list or queue, same as first, for a vector, same as, but much more efficient than, last. If the collection is em...

rest

Returns a possibly empty seq of the items after the first. Calls seq on its argument.

second

Same as (first (next x))

seq

Returns a seq on the collection. If the collection is empty, returns nil. (seq nil) returns nil. seq also works on ...

sequence

Coerces coll to a (possibly empty) sequence, if it is not already one. Will not force a lazy seq. (sequence nil) yield...

val

Returns the value in the map entry.

vals

Returns a sequence of the map's values, in the same order as (seq map).