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22.2.7 List Searching

The following procedures search lists for particular elements. They use different comparison predicates for comparing list elements with the object to be searched. When they fail, they return #f, otherwise they return the sublist whose car is equal to the search object, where equality depends on the equality predicate used.

— Scheme Procedure: memq x lst
— C Function: scm_memq (x, lst)

Return the first sublist of lst whose car is eq? to x where the sublists of lst are the non-empty lists returned by (list-tail lst k) for k less than the length of lst. If x is not in lst, then return #f.

— Scheme Procedure: memv x lst
— C Function: scm_memv (x, lst)

Return the first sublist of lst whose car is eqv? to x where the sublists of lst are the non-empty lists returned by (list-tail lst k) for k less than the length of lst. If x is not in lst, then return #f.

— Scheme Procedure: member x lst [=]
— C Function: scm_member (x, lst, =)

Return the first sublist of lst whose car is equal to x. If x does no appear in lst, return #f. Equality is determined by the equality predicate =, or equal? if = is not given.