title: Common lisp: Redefine an existing function within a scope?
body: <p>In Common Lisp, is it possible to redefine an already defined function within a certain scope? For example, given a function A that calls a function B. Can I temporarily redefine B during a call to A?</p>
  
  <p>I'm looking for something along the lines of a let block, but that can redefine functions.</p>