state transitions programs on github the strategy pattern why we use the strategy pattern sample code the context the program commands the line and bar graph strategies consequences of the strategy pattern programs on github the template pattern why we use template patterns kinds of methods in template class sample code drawing standard triangle drawing an isosceles triangle the triangle drawing program templates and callbacks summary and consequences example code on github the visitor pattern when to use the visitor pattern working with the visitor pattern sample code visiting each class visiting several classes bosses are employeestoo double dispatching traversing series of classes consequences of the visitor pattern example code on github xvii