Package java_cup
Class lr_item_core
- java.lang.Object
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- java_cup.lr_item_core
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- Direct Known Subclasses:
lalr_item
public class lr_item_core extends java.lang.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.- See Also:
lalr_item
,lalr_item_set
,lalr_state
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Field Summary
Fields Modifier and Type Field Description 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.
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Constructor Summary
Constructors Constructor Description lr_item_core(production prod)
Constructor for dot at start of right hand side.lr_item_core(production prod, int pos)
Full constructor.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
core_equals(lr_item_core other)
Equality comparison for the core only.int
core_hashCode()
Hash code for the core (separated so we keep non overridden version).boolean
dot_at_end()
Is the dot at the end of the production?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).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.boolean
equals(lr_item_core other)
Equality comparison.boolean
equals(java.lang.Object other)
Generic equality comparison.int
hashCode()
Hash code for the item.protected int
obj_hash()
Return the hash code that object would have provided for us so we have a (nearly) unique id for debugging.lr_item_core
shift_core()
Produce a new lr_item_core that results from shifting the dot one position to the right.symbol
symbol_after_dot()
Return the symbol after the dot.production
the_production()
The production for the item.java.lang.String
to_simple_string()
Convert to a string (separated out from toString() so we can call it from subclass that overrides toString()).java.lang.String
toString()
Convert to a string
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Field Detail
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_the_production
protected production _the_production
The production for the item.
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_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.
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_core_hash_cache
protected int _core_hash_cache
Cache of the hash code.
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_symbol_after_dot
protected symbol _symbol_after_dot
Cache of symbol after the dot.
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Constructor Detail
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lr_item_core
public lr_item_core(production prod, int pos) throws internal_error
Full constructor.- Parameters:
prod
- production this item uses.pos
- position of the "dot" within the item.- Throws:
internal_error
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lr_item_core
public lr_item_core(production prod) throws internal_error
Constructor for dot at start of right hand side.- Parameters:
prod
- production this item uses.- Throws:
internal_error
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Method Detail
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the_production
public production the_production()
The production for the item.
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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.
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dot_at_end
public boolean dot_at_end()
Is the dot at the end of the production?
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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.
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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).
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shift_core
public lr_item_core shift_core() throws internal_error
Produce a new lr_item_core that results from shifting the dot one position to the right.- Throws:
internal_error
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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.
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equals
public boolean equals(lr_item_core other)
Equality comparison.
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equals
public boolean equals(java.lang.Object other)
Generic equality comparison.- Overrides:
equals
in classjava.lang.Object
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core_hashCode
public int core_hashCode()
Hash code for the core (separated so we keep non overridden version).
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hashCode
public int hashCode()
Hash code for the item.- Overrides:
hashCode
in classjava.lang.Object
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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.
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to_simple_string
public java.lang.String to_simple_string() throws internal_error
Convert to a string (separated out from toString() so we can call it from subclass that overrides toString()).- Throws:
internal_error
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toString
public java.lang.String toString()
Convert to a string- Overrides:
toString
in classjava.lang.Object
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