The left corner of a production rule in a context-free grammar is the left-most symbol on the right side of the rule.
For example, in the rule A→Xα, X is the left corner.
The left corner table associates a symbol with all possible left corners for that symbol, and the left corners of those symbols, etc.
Given the grammar
- S→VP
- S→NP VP
- VP→V NP
- NP→DET N
Symbol | Left corner(s) |
---|---|
S | VP, NP, V, DET |
NP | Det |
VP | V |
Left corners are used to add bottom-up filtering of a top-down parser.
You can use the left corners to do top-down filtering of a bottom-up parser.
Famous quotes containing the words left and/or corner:
“Women ... are the permanent victims.”
—Jane OReilly, U.S. feminist and humorist. The Girl I Left Behind, ch. 6 (1980)
“Theres only one corner of the universe you can be certain of improving, and thats your own self.”
—Aldous Huxley (18941963)
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