doco srfi-1 alist-delete

[Kevin Ryde]

        * srfi-modules.texi (SRFI-1 Association Lists): In alist-delete and
        alist-delete!, note argument order in the equality calls, per SRFI-1
        spec.


 - Scheme Procedure: alist-delete key alist [=]
 - Scheme Procedure: alist-delete! key alist [=]
     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 `equal?' if not
     given.  The order in which elements are tested is unspecified, but
     each equality call is made `(= key alistkey)', ie. 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.