Package nltk :: Package parse :: Module chart :: Class TopDownPredictRule

type TopDownPredictRule

   object --+        
            |        
   ChartRuleI --+    
                |    
AbstractChartRule --+
                    |
                   TopDownPredictRule

Known Subclasses:

A rule licensing edges corresponding to the grammar productions for the nonterminal following an incomplete edge's dot. In particular, this rule specifies that:

[A → α * B β][i:j]

licenses the edge:

[B → * γ][j:j]

for each grammar production B → γ.

Note: This rule corresponds to the Predictor Rule in Earley parsing.

Instance Methods

[hide private]

iter of EdgeI

apply_iter(self, chart, grammar, edge)
Returns: A generator that will add edges licensed by this rule and the given edges to the chart, one at a time.

source code

Inherited from AbstractChartRule: __str__, apply, apply_everywhere, apply_everywhere_iter

Class Variables

[hide private]

int NUM_EDGES = 1
The number of existing edges that this rule uses to license new edges.

Method Details

[hide private]

apply_iter(self, chart, grammar, edge)

source code

Parameters:

edges - A set of existing edges. The number of edges that should be passed to apply is specified by the NUM_EDGES class variable.

Returns: iter of EdgeI

A generator that will add edges licensed by this rule and the given edges to the chart, one at a time. Each time the generator is resumed, it will either add a new edge and yield that edge; or return.

Overrides: ChartRuleI.apply_iter

(inherited documentation)