Sealable Metaobjects for Common Lisp

We introduce the concept of sealable metaobjects, i.e., classes, generic functions, and methods, whose behavior is restricted to allow for some static analysis. Then we use these sealable metaobjects to define fast generic functions, a variant of standard generic functions that allow for call site optimization --- ranging from faster method dispatch to inlining of entire effective methods. Fast generic functions support almost all features of standard generic functions, including custom method combinations and non-trivial references to the next method. Our benchmarks show that a straightforward implementation of Common Lisp's sequence functions using these fast generic functions is competitive with the corresponding built-in sequence functions of SBCL. Fast generic functions are thus an attractive drop-in replacement for standard generic functions in performance critical codes