Package java_cup

Class lr_item_core

  • 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
    • 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.
    • 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
      • Methods inherited from class java.lang.Object

        clone, finalize, getClass, notify, notifyAll, wait, wait, wait
    • Field Detail

      • _the_production

        protected production _the_production
        The production for the item.
      • _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.
      • _core_hash_cache

        protected int _core_hash_cache
        Cache of the hash code.
      • _symbol_after_dot

        protected symbol _symbol_after_dot
        Cache of symbol after the dot.
    • Constructor Detail

      • 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
      • 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
    • Method Detail

      • the_production

        public production the_production()
        The production for the item.
      • 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.
      • dot_at_end

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

        public boolean equals​(lr_item_core other)
        Equality comparison.
      • equals

        public boolean equals​(java.lang.Object other)
        Generic equality comparison.
        Overrides:
        equals in class java.lang.Object
      • core_hashCode

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

        public int hashCode()
        Hash code for the item.
        Overrides:
        hashCode in class java.lang.Object
      • 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.
      • 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
      • toString

        public java.lang.String toString()
        Convert to a string
        Overrides:
        toString in class java.lang.Object