ANSI Common Lisp 2 Syntax 2.4 Standard Macro Characters 2.4.8 Sharpsign
188.8.131.52 Sharpsign Dot
#.foo is read as the object resulting from the evaluation
of the object represented by foo.
The evaluation is done during the read process,
when the #. notation is encountered.
The #. syntax therefore performs a read-time evaluation of foo.
The normal effect of #. is inhibited when the value of *read-eval* is false.
In that situation, an error of type reader-error is signaled.
For an object
that does not have a convenient printed
representation, a form that computes the object can be given using
the #. notation.