eval.bsh

用java 编写的源码开放的文本编辑器。有很多有用的特性

/**
	Evaluate the string in the current interpreter (see source()).
	Returns the result of the evaluation or null.
	<p>

	Evaluate a string as if it were written directly in the current scope, 
	with side effects in the current scope.
	<p>
	e.g.
	<code><pre>
		a=5;
		eval("b=a*2");
		print(b); // 10
	</pre></code>
	<p>

	eval() acts just like invoked text except that any exceptions generated
	by the code are captured in a bsh.EvalError.  This includes ParseException
	for syntactic errors and TargetError for exceptions thrown by the evaluated
	code.
	<p>
	e.g.
	<pre>
		try {
			eval("foo>>><>M>JK$LJLK$");
		} catch ( EvalError e ) {
			// ParseException caught here
		}

		try {
			eval("(Integer)true");  // illegal cast
		} catch ( EvalError e ) {
			// TargetException caught here
			print( e.getTarget() )  // prints ClassCastException
		}
	</pre>
	<p>
	
	If you want eval() to throw target exceptions directly, without wrapping
	them, you can simply redefine own eval like so:

	<pre>
		myeval( String expression ) {
			try {
				return eval( expression );
			} catch ( TargetError e ) {
				throw e.getTarget();
			}
		}
	</pre>

	<p>
	Returns the value of the expression.
	<p>
	Throws bsh.EvalError on error
	<p>
	@return the value of the expression.
	@throws bsh.EvalError on error
*/

bsh.help.eval = "usage: eval( String expression )";

Object eval( String expression ) {
    return this.interpreter.eval( expression, this.caller.namespace );
}