Either a function object, a lambda expression or a symbol with a function definition.
If the function denoted by
is not compiled then it is first compiled using the function
. This happens if
is a lambda expression or an symbol naming an interpreted function.
The output from
lacks useful information such as local and lexical variable names and symbol names. The representation of integers or characters or Lisp objects in general is not easily readable without detailed knowledge of the internals of the Lisp system and the host machine instruction set.