Association lists are described in detail in section Association Lists. The present section only documents the additional procedures for dealing with association lists defined by SRFI-1.
Return the pair from alist which matches key. This
extends the core
assoc (see Retrieving Alist Entries) by
taking an optional = comparison procedure.
The default comparison is
equal?. If an = parameter is
given it’s called
(= key alistcar), i.e. the
given target key is the first argument, and a
alist is second.
For example a case-insensitive string lookup,
(assoc "yy" '(("XX" . 1) ("YY" . 2)) string-ci=?) ⇒ ("YY" . 2)
Cons a new association key and datum onto alist and return the result. This is equivalent to
(cons (cons key datum) alist)
acons (see Adding or Setting Alist Entries) in the Guile
core does the same thing.
Return a newly allocated copy of alist, that means that the spine of the list as well as the pairs are copied.
Return a list containing the elements of alist but with those elements whose keys are equal to key deleted. The returned elements will be in the same order as they were in alist.
Equality is determined by the = predicate, or
not given. The order in which elements are tested is unspecified, but
each equality call is made
(= key alistkey), i.e. the given
key parameter is first and the key from alist second.
This means for instance all associations with a key greater than 5 can
be removed with
(alist-delete 5 alist <).
alist-delete does not modify alist, but the return might
share a common tail with alist.
alist-delete! may modify
the list structure of alist to construct its return.