13 Functions

A Lisp program is composed mainly of Lisp functions. This chapter explains what functions are, how they accept arguments, and how to define them.

• What Is a Function		Lisp functions vs. primitives; terminology.
• Lambda Expressions		How functions are expressed as Lisp objects.
• Function Names		A symbol can serve as the name of a function.
• Defining Functions		Lisp expressions for defining functions.
• Calling Functions		How to use an existing function.
• Mapping Functions		Applying a function to each element of a list, etc.
• Anonymous Functions		Lambda expressions are functions with no names.
• Generic Functions		Polymorphism, Emacs-style.
• Function Cells		Accessing or setting the function definition of a symbol.
• Closures		Functions that enclose a lexical environment.
• Advising Functions		Adding to the definition of a function.
• Obsolete Functions		Declaring functions obsolete.
• Inline Functions		Functions that the compiler will expand inline.
• Declare Form		Adding additional information about a function.
• Declaring Functions		Telling the compiler that a function is defined.
• Function Safety		Determining whether a function is safe to call.
• Related Topics		Cross-references to specific Lisp primitives that have a special bearing on how functions work.