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:
“Laughter on American television has taken the place of the chorus in Greek tragedy.... In other countries, the business of laughing is left to the viewers. Here, their laughter is put on the screen, integrated into the show. It is the screen that is laughing and having a good time. You are simply left alone with your consternation.”
—Jean Baudrillard (b. 1929)
“O curse of marriage,
That we can call these delicate creatures ours
And not their appetites! I had rather be a toad,
And live upon the vapour of a dungeon
Than keep a corner in the thing I love
For others’ uses.”
—William Shakespeare (1564–1616)