An association in which key a is associated with value x, key b with value y, etc.:

Extract the value associated with key b:

Convert a list of rules to an association:

Convert an association to a list of rules:

Keys are "transparent" for many operations:

Position gives keys in an association:

Append to an association:

Delayed rules can be used to construct associations whose values are stored unevaluated:

The value in the association is evaluated when it is extracted:

Values in associations can be extracted like parts:

If the key in an association is a string, no explicit Key is needed to extract it as a part:

Numerical part specifications work structurally on associations:

Lookups in associations interoperate with parts in lists and other expressions:

The explicit Key can be omitted when the keys are strings:

Keys extracts the list of keys:

Associations can be modified by resetting values:

Associations work with any number of elements:

Extracting values from an association is highly efficient:

Associations can have arbitrary expressions as keys, including associations:

Missing elements are represented by Missing:

Lookup allows a default value to be given:

Associations can be used for pattern matching:

Extract key and value from an association:

Replace arguments of a function:

Pick the rule with the specific key:

Filter associations with length 2 only:

Define a function using an Association as an argument:

Use nested associations as a function argument:

KeyValuePattern lets you match any element in an association:

KeyValuePattern matches elements that appear anywhere in an association:

Values extracts values from an association:

Keys extracts keys from an association:

Normal turns an association into a list of rules:

Associations keep only the last instance of repeated keys:

When an association is modified, a new copy is created:

v is modified; w is unchanged:

Associations can have zero length:

Association counts as one level, not two, in structural functions:

Lists of rules are two levels:

Replacing the head of an Association loses keys:

Extract rules from an Association: