modify an association list by associating a value with a key
Major Section:  PROGRAMMING

(Put-assoc-eq name val alist) returns an alist that is the same as the list alist, except that the first pair in alist with a car of name is replaced by (cons name val), if there is one. If there is no such pair, then (cons name val) is added at the end. Note that the order of the keys occurring in alist is unchanged (though a new key may be added).

The guard of (put-assoc-eq name val alist) requires that alist is an alistp, and moreover, either name is a symbol or alist is a symbol-alistp.