7 Contracts

The Racket Guide

7.1 Contracts and Boundaries

7.2 Simple Contracts on Functions

7.3 Contracts on Functions in General

7.4 Contracts: A Thorough Example

7.5 Contracts on Structures

7.6 Abstract Contracts using #:exists and #:∃

7.7 Additional Examples

7.8 Building New Contracts

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7Contracts🔗 i

This chapter provides a gentle introduction to Racket’s contract system.

+Contracts in The Racket Reference provides more on contracts.

7.1Contracts and Boundaries

7.1.1Contract Violations

7.1.2Experimenting with Contracts and Modules

7.1.3Experimenting with Nested Contract Boundaries

7.2Simple Contracts on Functions

7.2.1Styles of ->

7.2.2Using define/contract and ->

7.2.3any and any/c

7.2.4Rolling Your Own Contracts

7.2.5Contracts on Higher-order Functions

7.2.6Contract Messages with “???”

7.2.7Dissecting a contract error message

7.3Contracts on Functions in General

7.3.1Optional Arguments

7.3.2Rest Arguments

7.3.3Keyword Arguments

7.3.4Optional Keyword Arguments

7.3.5Contracts for case-lambda

7.3.6Argument and Result Dependencies

7.3.7Checking State Changes

7.3.8Multiple Result Values

7.3.9Fixed but Statically Unknown Arities

7.4Contracts: A Thorough Example

7.5Contracts on Structures

7.5.1Guarantees for a Specific Value

7.5.2Guarantees for All Values

7.5.3Checking Properties of Data Structures

7.6Abstract Contracts using #:exists and #:∃

7.7Additional Examples

7.7.1A Customer-Manager Component

7.7.2A Parameteric (Simple) Stack

7.7.3A Dictionary

7.8Building New Contracts

7.8.1Contract Struct Properties

7.8.2With all the Bells and Whistles

7.9.1Contracts and eq?

7.9.2Contract boundaries and define/contract

7.9.3Exists Contracts and Predicates

7.9.4Defining Recursive Contracts

7.9.5Mixing set! and contract-out

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