Here is a common-lisp compiler using tagged pointers for some common objects. https://github.com/sbcl/sbcl/blob/master/doc/internals/objects-in-memory.texinfo h

Here is a common-lisp compiler using tagged pointers for some common objects. https://github.com/sbcl/sbcl/blob/master/doc/internals/objects-in-memory.texinfo https://github.com/sbcl/sbcl/blob/master/doc/internals/objec... That is how Lisps speedup list operations since it is the most used data structure.