97 lines
3.5 KiB
Factor
97 lines
3.5 KiB
Factor
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! :folding=indent:collapseFolds=1:
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! $Id$
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!
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! Copyright (C) 2004 Slava Pestov.
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!
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! Redistribution and use in source and binary forms, with or without
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! modification, are permitted provided that the following conditions are met:
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!
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! 1. Redistributions of source code must retain the above copyright notice,
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! this list of conditions and the following disclaimer.
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!
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! 2. Redistributions in binary form must reproduce the above copyright notice,
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! this list of conditions and the following disclaimer in the documentation
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! and/or other materials provided with the distribution.
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!
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! THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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! INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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! FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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! DEVELOPERS AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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! SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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! PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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! OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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! WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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! OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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! ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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IN: generic
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USE: errors
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USE: hashtables
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USE: kernel
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USE: lists
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USE: namespaces
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USE: parser
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USE: strings
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USE: words
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USE: vectors
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! A simple single-dispatch generic word system.
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: predicate-word ( word -- word )
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word-name "?" cat2 "in" get create ;
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! Terminology:
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! - type: a datatype built in to the runtime, eg fixnum, word
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! cons. All objects have exactly one type, new types cannot be
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! defined, and types are disjoint.
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! - class: a user defined way of differentiating objects, either
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! based on type, or some combination of type, predicate, or
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! method map.
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! - traits: a hashtable has traits of its traits slot is set to
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! a hashtable mapping selector names to method definitions.
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! The class of an object with traits is determined by the object
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! identity of the traits method map.
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! - metaclass: a metaclass is a symbol with a handful of word
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! properties: "define-method" "builtin-types"
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: metaclass ( class -- metaclass )
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"metaclass" word-property ;
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: builtin-supertypes ( class -- list )
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#! A list of builtin supertypes of the class.
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dup metaclass "builtin-supertypes" word-property call ;
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: add-method ( definition type vtable -- )
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>r "builtin-type" word-property r> set-vector-nth ;
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: define-generic ( word vtable -- )
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2dup "vtable" set-word-property
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[ generic ] cons define-compound ;
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: <vtable> ( default -- vtable )
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num-types [ drop dup ] vector-project nip ;
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DEFER: add-traits-dispatch
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! Defining generic words
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: GENERIC:
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#! GENERIC: bar creates a generic word bar that calls the
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#! bar method on the traits object, with the traits object
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#! on the stack.
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CREATE [ undefined-method ] <vtable>
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2dup add-traits-dispatch
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define-generic ; parsing
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: define-method ( class -- quotation )
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#! In a vain attempt at something resembling a "meta object
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#! protocol", we call the "define-method" word property with
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#! stack ( class generic definition -- ).
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metaclass "define-method" word-property
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[ [ undefined-method ] ] unless* ;
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: M: ( -- class generic [ ] )
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#! M: foo bar begins a definition of the bar generic word
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#! specialized to the foo type.
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scan-word dup define-method scan-word swap [ ] ; parsing
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