Package java_cup

Class non_terminal

java.lang.Object
java_cup.symbol
java_cup.non_terminal

public class non_terminal extends symbol
This class represents a non-terminal symbol in the grammar. Each non terminal has a textual name, an index, and a string which indicates the type of object it will be implemented with at runtime (i.e. the class of object that will be pushed on the parse stack to represent it).
Version:
last updated: 11/25/95
Author:
Scott Hudson
  • Field Details

    • _all

      protected static Hashtable _all
      Table of all non-terminals -- elements are stored using name strings as the key
    • _all_by_index

      protected static Hashtable _all_by_index
      Table of all non terminals indexed by their index number.
    • next_index

      protected static int next_index
      Static counter to assign unique indexes.
    • next_nt

      protected static int next_nt
      Static counter for creating unique non-terminal names
    • START_nt

      public static final non_terminal START_nt
      special non-terminal for start symbol
    • is_embedded_action

      public boolean is_embedded_action
      flag non-terminals created to embed action productions
    • _productions

      protected Hashtable _productions
      Table of all productions with this non terminal on the LHS.
    • _nullable

      protected boolean _nullable
      Nullability of this non terminal.
    • _first_set

      protected terminal_set _first_set
      First set for this non-terminal.
  • Constructor Details

    • non_terminal

      public non_terminal(String nm, String tp)
      Full constructor.
      Parameters:
      nm - the name of the non terminal.
      tp - the type string for the non terminal.
    • non_terminal

      public non_terminal(String nm)
      Constructor with default type.
      Parameters:
      nm - the name of the non terminal.
  • Method Details

    • clear

      public static void clear()
    • all

      public static Enumeration all()
      Access to all non-terminals.
    • find

      public static non_terminal find(String with_name)
      lookup a non terminal by name string
    • find

      public static non_terminal find(int indx)
      Lookup a non terminal by index.
    • number

      public static int number()
      Total number of non-terminals.
    • compute_nullability

      public static void compute_nullability() throws internal_error
      Compute nullability of all non-terminals.
      Throws:
      internal_error
    • compute_first_sets

      public static void compute_first_sets() throws internal_error
      Compute first sets for all non-terminals. This assumes nullability has already computed.
      Throws:
      internal_error
    • productions

      public Enumeration productions()
      Access to productions with this non terminal on the LHS.
    • num_productions

      public int num_productions()
      Total number of productions with this non terminal on the LHS.
    • add_production

      public void add_production(production prod) throws internal_error
      Add a production to our set of productions.
      Throws:
      internal_error
    • nullable

      public boolean nullable()
      Nullability of this non terminal.
    • first_set

      public terminal_set first_set()
      First set for this non-terminal.
    • is_non_term

      public boolean is_non_term()
      Indicate that this symbol is a non-terminal.
      Specified by:
      is_non_term in class symbol
    • looks_nullable

      protected boolean looks_nullable() throws internal_error
      Test to see if this non terminal currently looks nullable.
      Throws:
      internal_error
    • toString

      public String toString()
      convert to string
      Overrides:
      toString in class symbol