Designing Abstractions with First-Class Functions

We have seen that functions can consume functions and how important that is for creating single points of control in a function. But functions not only can consume functions, they can also produce them. More precisely, expressions in the new Scheme can evaluate to functions. Because the body of a function definition is also an expression, a function can produce a function. In this section, we first discuss this surprising idea and then show how it is useful for abstracting functions and in other contexts.

• Functions that Produce Functions
• Designing Abstractions with Functions-as-Values
• A First Look at Graphical User Interfaces