74 lines
2.2 KiB
Tal
74 lines
2.2 KiB
Tal
(
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binary tree node layout:
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+--+--+
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| ' | incoming-ptr*
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+--+--+ key: null optional
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v left right terminated binary
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| ptr ptr string data
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\ +--+--+--+--+---------+--+----- - -
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---> | ' | ' | U x n .00|
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+--+--+--+--+---------+--+----- - -
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All of the pointers (ptr) are shorts that have the value of the memory
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location of the next node, or 0000 to mean that pointer is empty. The very
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simplest tree is one where the incoming-ptr* is empty:
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+--+--+
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|00'00| incoming-ptr*
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+--+--+
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traverse-tree does two jobs at once, depending on whether the search-key is
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found:
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* if the search-key exists in the tree, return a pointer to the binary data
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that follows that node's key string;
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* if the search-key is not present in the key, return the incoming-ptr* that
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should be written when adding this node yourself.
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)
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@traverse-tree ( incoming-ptr* search-key* -- binary-ptr* 00 if key found
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OR node-incoming-ptr* 01 if key not found )
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STH2
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&loop ( incoming-ptr* / search-key* )
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LDA2k ORA ,&valid-node JCN
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POP2r #01 JMP2r
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&valid-node ( incoming-ptr* / search-key* )
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LDA2 ( node* / search-key* )
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DUP2 #0004 ADD2 ( node* node-key* / search-key* )
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STH2kr ( node* node-key* search-key* / search-key* )
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,strcmp JSR ( node* node-end* search-end* order nomatch / search-key* )
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,&nomatch JCN ( node* node-end* search-end* order / search-key* )
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POP POP2 ( node* node-end* / search-key* )
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INC2 NIP2 ( binary-ptr* / search-key* )
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POP2r #00 ( binary-ptr* 00 )
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JMP2r
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&nomatch ( node* node-end* search-end* order / search-key* )
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#80 AND #06 SFT #00 SWP STH2 ( node* node-end* search-end* / search-key* node-offset^ )
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POP2 POP2 ( node* / search-key* node-offset^ )
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STH2r ADD2 ( incoming-ptr* / search-key* )
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,&loop JMP
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@strcmp ( a* b* -- a-end* b-end* order nonzero if strings differ
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OR a-end* b-end* 00 00 if strings match )
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STH2
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,&entry JMP
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&loop ( a* a b / b* )
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SUB ,&nomatch JCNk ( a* a-b nonzero / b* )
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POP2 ( a* / b* )
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INC2 INC2r
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&entry ( a* / b* )
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LDAk LDAkr STHr ( a* a b / b* )
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ORAk ,&loop JCN
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&nomatch ( a* a-b flag / b* )
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STH2r SWP2 ( a* b* a-b flag )
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JMP2r
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