/// <summary>
/// Tries to parse an expression out of a given string.
/// </summary>
/// <param name="content">String to parse.</param>
/// <param name="expr">On success, receives the
/// expression.</param>
/// <returns>true on success; false otherwise.</returns>
public static bool TryParse(string content, out Expression expr)
{
var parser = new ExpressionParser(content);
return(parser.TryParse(out expr));
}