structure IR = RefFun.Make(struct type data = int end) structure SR = RefFun.Make(struct type data = string end) fun mutate () = ir <- IR.new 3; ir' <- IR.new 7; sr <- SR.new "hi"; IR.write ir' 10; iv <- IR.read ir; iv' <- IR.read ir'; sv <- SR.read sr; IR.delete ir; IR.delete ir'; SR.delete sr; return {[iv]}, {[iv']}, {[sv]} fun main () = return