1 files changed, 80 insertions, 0 deletions
diff --git a/src/main/java/io/devnulllabs/openjava/syntax/AbstractSyntaxRule.java b/src/main/java/io/devnulllabs/openjava/syntax/AbstractSyntaxRule.java
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index 0000000..33c6029
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+++ b/src/main/java/io/devnulllabs/openjava/syntax/AbstractSyntaxRule.java
@@ -0,0 +1,80 @@
+/*
+ * 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;
+    }
+
+}
+