update playground

tool/playground/A2.g4

@@ -0,0 +1,13 @@
+grammar A2;
+
+s : e {System.out.println($e.v);} ;
+
+e returns [int v]
+  : a=e '*' b=e {$v = $a.v * $b.v;}		-> Mult
+  | a=e '+' b=e {$v = $a.v + $b.v;}		-> Add
+  | INT         {$v = $INT.int;} 		-> Int
+  | '(' x=e ')' {$v = $x.v;} 			-> Parens
+  ;
+
+INT : [0-9]+ ;
+WS : [ \t\n]+ -> skip ;

tool/playground/TestA2.java

@@ -0,0 +1,84 @@
+/*
+ [The "BSD license"]
+ Copyright (c) 2011 Terence Parr
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+
+ 1. Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+ 3. The name of the author may not be used to endorse or promote products
+    derived from this software without specific prior written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+import org.antlr.v4.runtime.*;
+import org.antlr.v4.runtime.tree.ParseTreeWalker;
+
+public class TestA2 {
+	/** An example listener that squirrels away a return value in a field
+	 *  called v that we get added to the expression context objects
+	 *  by adding a return value to rule e. This is a version of A.g4
+	 *  that performs actions during the parse with user-defined actions.
+	 *  AND, we pass in a listener that gets executed during the parse
+	 *  and we use a listener on a tree walk that executes after the parse.
+	 *  So, it affect, we compute the result of the expression 3 times.
+	 */
+	public static class Do extends A2BaseListener {
+		A2Parser p;
+		public Do(A2Parser p) { this.p = p; }
+		@Override
+		public void exit(A2Parser.AddContext ctx) {
+			ctx.v = ctx.e(0).v + ctx.e(1).v;
+			System.out.println("Add: " + ctx.v);
+		}
+
+		@Override
+		public void exit(A2Parser.IntContext ctx) {
+			ctx.v = Integer.valueOf(ctx.INT().getText());
+			System.out.println("Int: "+ctx.v);
+		}
+
+		@Override
+		public void exit(A2Parser.MultContext ctx) {
+			ctx.v = ctx.e(0).v * ctx.e(1).v;
+			System.out.println("Mult: " + ctx.v);
+		}
+
+		@Override
+		public void exit(A2Parser.ParensContext ctx) {
+			ctx.v = ctx.e().v;
+			System.out.println("Parens: "+ctx.v);
+		}
+	}
+	public static void main(String[] args) throws Exception {
+		A2Lexer lexer = new A2Lexer(new ANTLRFileStream(args[0]));
+		CommonTokenStream tokens = new CommonTokenStream(lexer);
+		A2Parser p = new A2Parser(tokens);
+		p.setBuildParseTree(true);
+		p.addParseListener(new Do(p));
+		ParserRuleContext<Token> t = p.s();
+		System.out.println("tree = "+t.toStringTree(p));
+
+		ParseTreeWalker walker = new ParseTreeWalker();
+		Do doer = new Do(p);
+		walker.walk(doer, t);
+		A2Parser.eContext ectx = (A2Parser.eContext)t.getChild(0);
+		System.out.println("result from tree walk = "+ ectx.v);
+	}
+}