Homework 1

src/cd/ir/AstVisitor.java

@@ -0,0 +1,106 @@
+package cd.ir;
+
+import cd.ir.Ast.Decl;
+import cd.ir.Ast.Expr;
+import cd.ir.Ast.Stmt;
+
+/** A visitor that visits any kind of node */
+public class AstVisitor<R,A> extends ExprVisitor<R,A> {
+	
+	/** 
+	 * Recurse and process {@code ast}.  It is preferred to 
+	 * call this rather than calling accept directly, since
+	 * it can be overloaded to introduce memoization, 
+	 * for example. */
+	public R visit(Ast ast, A arg) {
+		return ast.accept(this, arg);
+	}
+	
+	/**
+	 * A handy function which visits the children of {@code ast},
+	 * providing "arg" to each of them.  It returns the result of
+	 * the last child in the list.  It is invoked by the method 
+	 * {@link #dflt(Ast, Object)} by default.
+	 */
+	public R visitChildren(Ast ast, A arg) {
+		R lastValue = null;
+		for (Ast child : ast.children())
+			lastValue = visit(child, arg);
+		return lastValue;
+	}
+	
+	/** 
+	 * The default action for default actions is to call this,
+	 * which simply recurses to any children.  Also called
+	 * by seq() by default. */
+	protected R dflt(Ast ast, A arg) {
+		return visitChildren(ast, arg);
+	}
+	
+	/** 
+	 * The default action for statements is to call this */
+	protected R dfltStmt(Stmt ast, A arg) {
+		return dflt(ast, arg);
+	}
+	
+	/** 
+	 * The default action for expressions is to call this */
+	protected R dfltExpr(Expr ast, A arg) {
+		return dflt(ast, arg);
+	}
+
+	/** 
+	 * The default action for AST nodes representing declarations
+	 * is to call this function */
+	protected R dfltDecl(Decl ast, A arg) {
+		return dflt(ast, arg);
+	}
+	
+	public R assign(Ast.Assign ast, A arg) {
+		return dfltStmt(ast, arg);
+	}
+
+	public R builtInWrite(Ast.BuiltInWrite ast, A arg) {
+		return dfltStmt(ast, arg);
+	}
+
+	public R builtInWriteln(Ast.BuiltInWriteln ast, A arg) {
+		return dfltStmt(ast, arg);
+	}
+	
+	public R classDecl(Ast.ClassDecl ast, A arg) {
+		return dfltDecl(ast, arg);
+	}
+	
+	public R methodDecl(Ast.MethodDecl ast, A arg) {
+		return dfltDecl(ast, arg);
+	}
+			
+	public R varDecl(Ast.VarDecl ast, A arg) {
+		return dfltDecl(ast, arg);
+	}
+	
+	public R ifElse(Ast.IfElse ast, A arg) {
+		return dfltStmt(ast, arg);
+	}
+	
+	public R returnStmt(Ast.ReturnStmt ast, A arg) {
+		return dfltStmt(ast, arg);
+	}
+
+	public R methodCall(Ast.MethodCall ast, A arg) {
+		return dfltStmt(ast, arg);
+	}
+
+	public R nop(Ast.Nop ast, A arg) {
+		return dfltStmt(ast, arg);
+	}
+	
+	public R seq(Ast.Seq ast, A arg) {
+		return dflt(ast, arg);
+	}
+	
+	public R whileLoop(Ast.WhileLoop ast, A arg) {
+		return dfltStmt(ast, arg);
+	}
+}