factor/basis/stack-checker/recursive-state/tree/tree.factor

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! Copyright (C) 2008 Slava Pestov.
! See http://factorcode.org/license.txt for BSD license.
USING: accessors kernel sequences math math.order ;
IN: stack-checker.recursive-state.tree
! Persistent unbalanced hash tree using eq? comparison.
! We use this to speed up stack-checker.recursive-state.
! Perhaps this should go somewhere else
TUPLE: node value key hashcode left right ;
GENERIC: lookup ( key node -- value/f )
M: f lookup nip ;
: decide ( key node -- key node ? )
over hashcode over hashcode>> <= ; inline
M: node lookup
2dup key>> eq?
[ nip value>> ]
[ decide [ left>> ] [ right>> ] if lookup ] if ;
GENERIC: store ( value key node -- node' )
M: f store drop dup hashcode f f node boa ;
M: node store
clone decide
[ [ store ] change-left ]
[ [ store ] change-right ] if ;