java_cup-0.11a.src.java_cup.parse_action_table Maven / Gradle / Ivy
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CUP is a system for generating LALR parsers from simple specifications. It serves the same role as
the widely used program YACC [1] and in fact offers most of the features of YACC. However, CUP is
written in Java, uses specifications including embedded Java code, and produces parsers which are
implemented in Java.
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package java_cup;
import java.util.Enumeration;
/** This class represents the complete "action" table of the parser.
* It has one row for each state in the parse machine, and a column for
* each terminal symbol. Each entry in the table represents a shift,
* reduce, or an error.
*
* @see java_cup.parse_action
* @see java_cup.parse_action_row
* @version last updated: 11/25/95
* @author Scott Hudson
*/
public class parse_action_table {
/*-----------------------------------------------------------*/
/*--- Constructor(s) ----------------------------------------*/
/*-----------------------------------------------------------*/
/** Simple constructor. All terminals, non-terminals, and productions must
* already have been entered, and the viable prefix recognizer should
* have been constructed before this is called.
*/
public parse_action_table()
{
/* determine how many states we are working with */
_num_states = lalr_state.number();
/* allocate the array and fill it in with empty rows */
under_state = new parse_action_row[_num_states];
for (int i=0; i<_num_states; i++)
under_state[i] = new parse_action_row();
}
/*-----------------------------------------------------------*/
/*--- (Access to) Instance Variables ------------------------*/
/*-----------------------------------------------------------*/
/** How many rows/states are in the machine/table. */
protected int _num_states;
/** How many rows/states are in the machine/table. */
public int num_states() {return _num_states;}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/** Actual array of rows, one per state. */
public parse_action_row[] under_state;
/*-----------------------------------------------------------*/
/*--- General Methods ---------------------------------------*/
/*-----------------------------------------------------------*/
/** Check the table to ensure that all productions have been reduced.
* Issue a warning message (to System.err) for each production that
* is never reduced.
*/
public void check_reductions()
throws internal_error
{
parse_action act;
production prod;
/* tabulate reductions -- look at every table entry */
for (int row = 0; row < num_states(); row++)
{
for (int col = 0; col < parse_action_row.size(); col++)
{
/* look at the action entry to see if its a reduce */
act = under_state[row].under_term[col];
if (act != null && act.kind() == parse_action.REDUCE)
{
/* tell production that we used it */
((reduce_action)act).reduce_with().note_reduction_use();
}
}
}
/* now go across every production and make sure we hit it */
for (Enumeration p = production.all(); p.hasMoreElements(); )
{
prod = (production)p.nextElement();
/* if we didn't hit it give a warning */
if (prod.num_reductions() == 0)
{
/* count it *
emit.not_reduced++;
/* give a warning if they haven't been turned off */
if (!emit.nowarn)
{
ErrorManager.getManager().emit_warning("*** Production \"" +
prod.to_simple_string() + "\" never reduced");
}
}
}
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*
/** Convert to a string. */
public String toString()
{
String result;
int cnt;
result = "-------- ACTION_TABLE --------\n";
for (int row = 0; row < num_states(); row++)
{
result += "From state #" + row + "\n";
cnt = 0;
for (int col = 0; col < parse_action_row.size(); col++)
{
/* if the action is not an error print it */
if (under_state[row].under_term[col].kind() != parse_action.ERROR)
{
result += " [term " + col + ":" + under_state[row].under_term[col] + "]";
/* end the line after the 2nd one */
cnt++;
if (cnt == 2)
{
result += "\n";
cnt = 0;
}
}
}
/* finish the line if we haven't just done that */
if (cnt != 0) result += "\n";
}
result += "------------------------------";
return result;
}
/*-----------------------------------------------------------*/
}