Warning: This is the manual of the legacy Guile 2.2 series. You may want to read the manual of the current stable series instead.

6.6.20.3 Retrieving Alist Entries

assq, assv and assoc find the entry in an alist for a given key, and return the (key . value) pair. assq-ref, assv-ref and assoc-ref do a similar lookup, but return just the value.

Scheme Procedure: assq key alist

Scheme Procedure: assv key alist

Scheme Procedure: assoc key alist

C Function: scm_assq (key, alist)

C Function: scm_assv (key, alist)

C Function: scm_assoc (key, alist)

Return the first entry in alist with the given key. The return is the pair (KEY . VALUE) from alist. If there’s no matching entry the return is #f.

assq compares keys with eq?, assv uses eqv? and assoc uses equal?. See also SRFI-1 which has an extended assoc (SRFI-1 Association Lists).

Scheme Procedure: assq-ref alist key

Scheme Procedure: assv-ref alist key

Scheme Procedure: assoc-ref alist key

C Function: scm_assq_ref (alist, key)

C Function: scm_assv_ref (alist, key)

C Function: scm_assoc_ref (alist, key)

Return the value from the first entry in alist with the given key, or #f if there’s no such entry.

assq-ref compares keys with eq?, assv-ref uses eqv? and assoc-ref uses equal?.

Notice these functions have the key argument last, like other -ref functions, but this is opposite to what assq etc above use.

When the return is #f it can be either key not found, or an entry which happens to have value #f in the cdr. Use assq etc above if you need to differentiate these cases.