java_cup-0.11a.src.java_cup.parse_action_row 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;
/** This class represents one row (corresponding to one machine state) of the
* parse action table.
*/
public class parse_action_row {
/*-----------------------------------------------------------*/
/*--- Constructor(s) ----------------------------------------*/
/*-----------------------------------------------------------*/
/** Simple constructor. Note: this should not be used until the number of
* terminals in the grammar has been established.
*/
public parse_action_row()
{
/* make sure the size is set */
if (_size <= 0 ) _size = terminal.number();
/* allocate the array */
under_term = new parse_action[size()];
/* set each element to an error action */
for (int i=0; i<_size; i++)
under_term[i] = new parse_action();
}
/*-----------------------------------------------------------*/
/*--- (Access to) Static (Class) Variables ------------------*/
/*-----------------------------------------------------------*/
/** Number of columns (terminals) in every row. */
protected static int _size = 0;
/** Number of columns (terminals) in every row. */
public static int size() {return _size;}
//Hm Added clear to clear all static fields
public static void clear() {
_size = 0;
reduction_count = null;
}
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/** Table of reduction counts (reused by compute_default()). */
protected static int reduction_count[] = null;
/*-----------------------------------------------------------*/
/*--- (Access to) Instance Variables ------------------------*/
/*-----------------------------------------------------------*/
/** Actual action entries for the row. */
public parse_action under_term[];
/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
/** Default (reduce) action for this row. -1 will represent default
* of error.
*/
public int default_reduce;
/*-----------------------------------------------------------*/
/*--- General Methods ---------------------------------------*/
/*-----------------------------------------------------------*/
/** Compute the default (reduce) action for this row and store it in
* default_reduce. In the case of non-zero default we will have the
* effect of replacing all errors by that reduction. This may cause
* us to do erroneous reduces, but will never cause us to shift past
* the point of the error and never cause an incorrect parse. -1 will
* be used to encode the fact that no reduction can be used as a
* default (in which case error will be used).
*/
public void compute_default()
{
int i, prod, max_prod, max_red;
/* if we haven't allocated the count table, do so now */
if (reduction_count == null)
reduction_count = new int[production.number()];
/* clear the reduction count table and maximums */
for (i = 0; i < production.number(); i++)
reduction_count[i] = 0;
max_prod = -1;
max_red = 0;
/* walk down the row and look at the reduces */
for (i = 0; i < size(); i++)
if (under_term[i].kind() == parse_action.REDUCE)
{
/* count the reduce in the proper production slot and keep the
max up to date */
prod = ((reduce_action)under_term[i]).reduce_with().index();
reduction_count[prod]++;
if (reduction_count[prod] > max_red)
{
max_red = reduction_count[prod];
max_prod = prod;
}
}
/* record the max as the default (or -1 for not found) */
default_reduce = max_prod;
}
/*-----------------------------------------------------------*/
}
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