Collections Cheat Sheet

Common Collection Types

Class	Location	Description
<array>	dylan:dylan	Multi-dimensional data, much like a matrix.
<vector>	dylan:dylan	A one-dimensional array. Vectors provide fast random access.
<stretchy-vector>	dylan:dylan	A vector that can have elements directly added and removed without requiring a complete copy.
<list>	dylan:dylan	A linked list.
<deque>	dylan:dylan	A double-ended queue.
<set>	collections:set	A set is for efficiently tracking membership.
<bit-set>	collections:bit-set	A set with bits for members.
<bit-vector>	collections:bit-vector	A vector optimized for storing bit values.
<byte-vector>	collections:byte-vector	A vector of bytes.
<table>	dylan:dylan	A mapping between keys and values.
<string-table>	collections:table-extensions	A <table> with strings for keys.

Note

Because of the default comparison function for <table>, it is important to use <string-table> when the keys will be strings.

Mutable vs. Immutable

Many operations don’t modify the collection passed in. The exception is when you use an operation ending in ! on a stretchy collection.

For this reason, if you want to modify a collection frequently, be sure to pay attention to the type of collection that you’re working with.

In many cases, you will need to assign the result of an operation back to the source collection:

threads := add(threads, thread);

In cases where you are modifying a collection frequently, you may want to consider using a <stretchy-vector> rather than a <vector> or some other type of collection.

Common Operations

Class	Operation	Summary
<collection>	any?	Returns the first true value obtained by iterating over one or more collections.
	do	Iterates over one or more collections for side effect.
	empty?	Returns true if its argument is empty.
	every?	Returns true if a predicate returns true when applied to all corresponding elements of a set of collections.
	fill!	Fills a collection with a specified value.
	find-key	Returns the key in a collection such that the corresponding collection element satisfies a predicate.
	key-sequence	Returns a sequence containing the keys of its collection argument. This is commonly used with <table> instances.
	map	Iterates over one or more collections and collects the results in a freshly allocated collection. See also map-as and map-into.
	member?	Returns true if a collection contains a particular value.
	reduce	Combines the elements of a collection and a seed value into a single value by repeatedly applying a binary function. See also reduce1.
	replace-elements!	Replaces those collection elements that satisfy a predicate.
	size	Returns the size of its argument.
<sequence>	add / add!	Adds an element to a sequence.
	add-new / add-new!	Adds a new element to a sequence.
	choose	Returns those elements of a sequence that satisfy a predicate. See also choose-by.
	concatenate	Returns the concatenation of one or more sequences in a sequence of a type determined by the type-for-copy of its first argument. See also concatenate-as.
	copy-sequence	Returns a freshly allocated copy of some subsequence of a sequence.
	intersection	Returns the intersection of two sequences.
	remove / remove!	Removes an element from a sequence.
	remove-duplicates	Returns a sequence without duplicates.
	replace-subsequence!	Replaces a portion of a sequence with the elements of another sequence.
	reverse / reverse!	Returns a sequence with elements in the reverse order of its argument sequence.
	sort / sort!	Returns a sequence containing the elements of its argument sequence, sorted.
	subsequence-position	Returns the position where a pattern appears in a sequence.
	union	Returns the union of two sequences.
<list>	head	Returns the head of a list.
	tail	Returns the tail of a list.
<deque>	push	Adds an element to the front of a deque.
	pop	Removes and returns the first element of a deque.
	push-last	Adds an element to the end of a deque.
	pop-last	Removes and returns an element from the end of a deque.
<table>	remove-key!	Modifies an explicit key collection so it no longer has a particular key.