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.