[procedure] assoc obj alist

R5RS: finds the first pair in alist whose car field is obj, and returns that pair. If no pair in alist has obj as its car, then #f is returned. Uses equal? to compare.

See also assq, assv

[procedure] assoc obj alist [=]

SRFI-1 extends R5RS to allow the client to pass in an optional equality procedure = used to compare keys.