Chapter 5. Forests, etc.

Get the nodes in the graph.

Get the options for this forest.

How many parse trees are there in this forest?

In an infinitely ambiguous graph, there are an infinite number of parse trees. However, CoffeeGrinder will never follow the same edge twice when constructing a tree, it won’t loop. So the number of available trees is always a finite number.

Is the grammar represented by this graph ambiguous?

A grammar is ambiguous if there are more than two parses that will recognize the input.

Is the grammar represented by this graph infinitely ambiguous?

If the answer is “true”, then the graph is infinitely ambiguous. If the graph is ambiguous and the anwer is “false”, then all that can be said is the single parse explored to check ambiguity did not encounter infinite ambiguity. It is not an assertion that no unexplored part of the graph contains a loop.

Serialize the graph as XML.

Serialize the graph as XML.

Serialize the graph as XML.

This method attempts to write the XML to a file.

How big is the graph?

Who’s using this axe?

Do not pass the same axe to more than one Arborist.

Is this a specialist axe?

A specialist axe can consider every tree in the forest differently every time it is used. A non-specialist axe considers every tree at most once and returns all the trees that are selected.

Select a branch from a list of branches.

In an ambiguous forest, some nodes will have more than one possible choice. In any given tree, only one choice may be selected. This function is called to make the selection.

There will always be at least one element in the choices list when the method is called. The method must return at least one.

The first node in the list returned is the choice selected for the tree currently under construction. If only one choice is returned, the node becomes unambiguous on subsequent parses, the same selection will always be used. If additional choices are returned, they will be considered on subsequent parses. Note that if you want the selected choice to be considered on future parses, it must appear in the list twice. It is the only node that may appear twice.

Was the previous selection ambiguous?

This method asks if the previous selection was ambiguous. If the axe ever indicates that an ambiguous selection was made, the resulting parse is considered ambiguous. For example, the SequentialAxe always returns true because it treats all choices as equivalent. The PriorityAxe only considers a selection ambiguous if there wasn’t a uniquely highest priority selection.

Who’s using this axe?

Do not pass the same axe to more than one Arborist.

Is this a specialist axe?

A specialist axe can consider every tree in the forest differently every time it is used. A non-specialist axe considers every tree at most once and returns all the trees that are selected.

Select a branch from a list of branches.

In an ambiguous forest, some nodes will have more than one possible choice. In any given tree, only one choice may be selected. This function is called to make the selection.

There will always be at least one element in the choices list when the method is called. The method must return at least one.

The first node in the list returned is the choice selected for the tree currently under construction. If only one choice is returned, the node becomes unambiguous on subsequent parses, the same selection will always be used. If additional choices are returned, they will be considered on subsequent parses. Note that if you want the selected choice to be considered on future parses, it must appear in the list twice. It is the only node that may appear twice.

Was the previous selection ambiguous?

This method asks if the previous selection was ambiguous. If the axe ever indicates that an ambiguous selection was made, the resulting parse is considered ambiguous. For example, the SequentialAxe always returns true because it treats all choices as equivalent. The PriorityAxe only considers a selection ambiguous if there wasn’t a uniquely highest priority selection.

Who’s using this axe?

Do not pass the same axe to more than one Arborist.

Is this a specialist axe?

A specialist axe can consider every tree in the forest differently every time it is used. A non-specialist axe considers every tree at most once and returns all the trees that are selected.

Select a branch from a list of branches.

In an ambiguous forest, some nodes will have more than one possible choice. In any given tree, only one choice may be selected. This function is called to make the selection.

There will always be at least one element in the choices list when the method is called. The method must return at least one.

The first node in the list returned is the choice selected for the tree currently under construction. If only one choice is returned, the node becomes unambiguous on subsequent parses, the same selection will always be used. If additional choices are returned, they will be considered on subsequent parses. Note that if you want the selected choice to be considered on future parses, it must appear in the list twice. It is the only node that may appear twice.

Was the previous selection ambiguous?

This method asks if the previous selection was ambiguous. If the axe ever indicates that an ambiguous selection was made, the resulting parse is considered ambiguous. For example, the SequentialAxe always returns true because it treats all choices as equivalent. The PriorityAxe only considers a selection ambiguous if there wasn’t a uniquely highest priority selection.

Who’s using this axe?

Do not pass the same axe to more than one Arborist.

Is this a specialist axe?

A specialist axe can consider every tree in the forest differently every time it is used. A non-specialist axe considers every tree at most once and returns all the trees that are selected.

Select a branch from a list of branches.

In an ambiguous forest, some nodes will have more than one possible choice. In any given tree, only one choice may be selected. This function is called to make the selection.

There will always be at least one element in the choices list when the method is called. The method must return at least one.

The first node in the list returned is the choice selected for the tree currently under construction. If only one choice is returned, the node becomes unambiguous on subsequent parses, the same selection will always be used. If additional choices are returned, they will be considered on subsequent parses. Note that if you want the selected choice to be considered on future parses, it must appear in the list twice. It is the only node that may appear twice.

Was the previous selection ambiguous?

This method asks if the previous selection was ambiguous. If the axe ever indicates that an ambiguous selection was made, the resulting parse is considered ambiguous. For example, the SequentialAxe always returns true because it treats all choices as equivalent. The PriorityAxe only considers a selection ambiguous if there wasn’t a uniquely highest priority selection.

Called at the end of an ambiguity that is not marked by a single nonterminal.

Called when a nonterminal ends.

Called last, when construction finishes.

Called at the start of an ambiguity that is not marked by a single nonterminal.

The ambiguity id will distinguish this ambiguity from any other ambiguity. The numbers are not sequential or guaranteed stable across parses.

Called when a new nonterminal begins.

Called first, when construction begins.

Called when a terminal occurs.