blob: 33c602938e61b32f58aa835033d50686fcf98657 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
/*
* AbstractSyntaxRule.java
*
* comments here.
*
* @author Michiaki Tatsubori
* @version %VERSION% %DATE%
* @see java.lang.Object
*
* COPYRIGHT 1998 by Michiaki Tatsubori, ALL RIGHTS RESERVED.
*/
package io.devnulllabs.openjava.syntax;
import io.devnulllabs.openjava.ptree.ParseTree;
/**
* The interface <code>AbstractSyntaxRule</code> represents a syntax rule.
* <p>
*
* @author Michiaki Tatsubori
* @version 1.0
* @since $Id: AbstractSyntaxRule.java,v 1.2 2003/02/19 02:54:31 tatsubori Exp $
* @see java.lang.Object
*/
public abstract class AbstractSyntaxRule implements SyntaxRule
{
/**
* Consumes tokens from the given token source following
* the rule. To be overridden.
*
* @param token_src token source to consume.
* @return a parse tree object consumed by following this rule.
*/
public abstract ParseTree consume( TokenSource token_src )
throws SyntaxException;
/**
* Tests if the given token source follows this rule.
*
* @param token_src token source to consume.
* @return true if the given token source can be consumed safely.
*/
public final boolean lookahead( TokenSource token_src ) {
try {
RestorableTokenSource dummy
= new RestorableTokenSource( token_src );
consume( dummy );
return true;
} catch (SyntaxException e) {
setSyntaxException( e );
return false;
}
}
private SyntaxException lastException = null;
/**
* Obtains the syntax exception at the last lookahead.
* through the method <tt>lookahead(TokenSource)</tt>.
*
* @return the syntax exception.
*/
public final SyntaxException getSyntaxException() {
return lastException;
}
/**
* Sets the last syntax exception in consuming token source
* through the method <tt>consume(TokenSource)</tt>.
*
* @return the syntax exception.
*/
private final void setSyntaxException( SyntaxException e ) {
lastException = e;
}
}
|
