java_cup

Class lr_item_core

public class lr_item_core extends Object

The "core" of an LR item. This includes a production and the position of a marker (the "dot") within the production. Typically item cores are written using a production with an embedded "dot" to indicate their position. For example:
     A ::= B * C d E
  
This represents a point in a parse where the parser is trying to match the given production, and has succeeded in matching everything before the "dot" (and hence is expecting to see the symbols after the dot next). See lalr_item, lalr_item_set, and lalr_start for full details on the meaning and use of items.

Version: last updated: 11/25/95

Author: Scott Hudson

See Also: lalr_item lalr_item_set lalr_state

Field Summary
protected int_core_hash_cache
Cache of the hash code.
protected int_dot_pos
The position of the "dot" -- this indicates the part of the production that the marker is before, so 0 indicates a dot at the beginning of the RHS.
protected symbol_symbol_after_dot
Cache of symbol after the dot.
protected production_the_production
The production for the item.
Constructor Summary
lr_item_core(production prod, int pos)
Full constructor.
lr_item_core(production prod)
Constructor for dot at start of right hand side.
Method Summary
booleancore_equals(lr_item_core other)
Equality comparison for the core only.
intcore_hashCode()
Hash code for the core (separated so we keep non overridden version).
booleandot_at_end()
Is the dot at the end of the production?
non_terminaldot_before_nt()
Determine if we have a dot before a non terminal, and if so which one (return null or the non terminal).
intdot_pos()
The position of the "dot" -- this indicates the part of the production that the marker is before, so 0 indicates a dot at the beginning of the RHS.
booleanequals(lr_item_core other)
Equality comparison.
booleanequals(Object other)
Generic equality comparison.
inthashCode()
Hash code for the item.
protected intobj_hash()
Return the hash code that object would have provided for us so we have a (nearly) unique id for debugging.
lr_item_coreshift_core()
Produce a new lr_item_core that results from shifting the dot one position to the right.
symbolsymbol_after_dot()
Return the symbol after the dot.
productionthe_production()
The production for the item.
StringtoString()
Convert to a string
Stringto_simple_string()
Convert to a string (separated out from toString() so we can call it from subclass that overrides toString()).

Field Detail

_core_hash_cache

protected int _core_hash_cache
Cache of the hash code.

_dot_pos

protected int _dot_pos
The position of the "dot" -- this indicates the part of the production that the marker is before, so 0 indicates a dot at the beginning of the RHS.

_symbol_after_dot

protected symbol _symbol_after_dot
Cache of symbol after the dot.

_the_production

protected production _the_production
The production for the item.

Constructor Detail

lr_item_core

public lr_item_core(production prod, int pos)
Full constructor.

Parameters: prod production this item uses. pos position of the "dot" within the item.

lr_item_core

public lr_item_core(production prod)
Constructor for dot at start of right hand side.

Parameters: prod production this item uses.

Method Detail

core_equals

public boolean core_equals(lr_item_core other)
Equality comparison for the core only. This is separate out because we need separate access in a super class.

core_hashCode

public int core_hashCode()
Hash code for the core (separated so we keep non overridden version).

dot_at_end

public boolean dot_at_end()
Is the dot at the end of the production?

dot_before_nt

public non_terminal dot_before_nt()
Determine if we have a dot before a non terminal, and if so which one (return null or the non terminal).

dot_pos

public int dot_pos()
The position of the "dot" -- this indicates the part of the production that the marker is before, so 0 indicates a dot at the beginning of the RHS.

equals

public boolean equals(lr_item_core other)
Equality comparison.

equals

public boolean equals(Object other)
Generic equality comparison.

hashCode

public int hashCode()
Hash code for the item.

obj_hash

protected int obj_hash()
Return the hash code that object would have provided for us so we have a (nearly) unique id for debugging.

shift_core

public lr_item_core shift_core()
Produce a new lr_item_core that results from shifting the dot one position to the right.

symbol_after_dot

public symbol symbol_after_dot()
Return the symbol after the dot. If there is no symbol after the dot we return null.

the_production

public production the_production()
The production for the item.

toString

public String toString()
Convert to a string

to_simple_string

public String to_simple_string()
Convert to a string (separated out from toString() so we can call it from subclass that overrides toString()).