GENERIC-CL provides a generic function wrapper over various functions in the Common Lisp standard, such as equality predicates and sequence operations. The goal of this wrapper is to provide a standard interface to common operations, such as testing for the equality of two objects, which is extensible to user-defined types.
In Common lisp you have a number of different equality comparison functions for different object types. Worse still you have to invent a new name for the comparison functions for each of your own object types.
Standard Common Lisp:
(eq 'a x) ;; Symbols
(= 1 2) ;; Numbers
(equal '(1 2 3) x) ;; Lists
(equal "hello" y) ;; Strings
(equalp #(1 2 3) z) ;; Arrays
(foo-equal x y) ;; Instances of class fooIn GENERIC-CL there is a single equality predicate = which can be
used on objects of any builtin type. Since it's implemented using
generic functions, it can be extended with methods for user-defined
classes and structures.
Using GENERIC-CL:
(= 'a x) ;; Symbols
(= 1 2) ;; Numbers
(= '(1 2 3) x) ;; Lists
(= "hello" y) ;; Strings
(= #(1 2 3) z) ;; Arrays
(= x y) ;; Instances of class fooGENERIC-CL also provides generic interfaces for comparison (<, >,
...) functions, copying objects, iteration, sequence operations,
hash-tables capable of storing keys of user defined classes, and many
more.
Full documentation is available online in HTML format at
https://alex-gutev.github.io/generic-cl/, and also in AsciiDoc
format in the doc/ folder.
Generic functions do carry an additional overhead over ordinary functions, however this isn't a significant issue for most applications.
For those applications where the speed of generic-functions is an issue, generic function calls can be optimized, using static-dispatch on which this library is built, to be as efficient (and sometimes even more efficient) as ordinary function calls, when the types of the arguments are known at compile-time. Check out the Optimization section for more information.