lispdoc  results for subst 
(subst new old tree &key key (test #'eql testp) (testnot #'eql notp))  Function: Substitutes new for subtrees matching old.

Example:(defun integratefromtable (op arg) (let ((rule (get op 'int))) (subst arg (explhs (explhs (explhs rule))) (exprhs rule))))  Mentioned in: CLtL2  14.3. Modifying Sequences CLtL2  15.4. Substitution of Expressions HyperSpec  Function SUBST, SUBSTIF, SUBSTIFNOT, NSUBST, NSUBSTIF, NSUBSTIFNOT PCL  trees 
(substif new test tree &key key)  Function: Substitutes new for subtrees for which test is true.

Mentioned in: CLtL2  15.4. Substitution of Expressions HyperSpec  Function SUBST, SUBSTIF, SUBSTIFNOT, NSUBST, NSUBSTIF, NSUBSTIFNOT PCL  trees  
(substifnot new test tree &key key)  Function: Substitutes new for subtrees for which test is false.

Mentioned in: CLtL2  15.4. Substitution of Expressions HyperSpec  Function SUBST, SUBSTIF, SUBSTIFNOT, NSUBST, NSUBSTIF, NSUBSTIFNOT PCL  trees  
(subsetp list1 list2 &key key (test #'eql testp) (testnot nil notp))  Function: Return T if every element in LIST1 is also in LIST2.

Example:(defun setdiff (x y) (if (subsetp y x) (orderedsetdifference x y)))  Mentioned in: CLtL2  15.5. Using Lists as Sets HyperSpec  Function SUBSETP PCL  sets 
subsets  
Mentioned in: HyperSpec  1.7 Language Subsets  
By Bill Moorier 