The Typed Racket Guide

2 Beginning Typed Racket

3 Specifying Types

4 Types in Typed Racket

5 Occurrence Typing

6 Typed-Untyped Interaction

7 Optimization in Typed Racket

8 Caveats and Limitations

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The Typed Racket Guide

8.18

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The Typed Racket Guide🔗 i

Sam Tobin-Hochstadt <samth@racket-lang.org>,
Vincent St-Amour <stamourv@racket-lang.org>,
Eric Dobson <endobson@racket-lang.org>,
and Asumu Takikawa <asumu@racket-lang.org>

Typed Racket is Racket’s gradually-typed sister language which allows the incremental addition of statically-checked type annotations. This guide is intended for programmers familiar with Racket. For an introduction to Racket, see The Racket Guide.

For the precise details, also see The Typed Racket Reference.

1.1Using Typed Racket from the Racket REPL

2Beginning Typed Racket

2.1Datatypes and Unions

3Specifying Types

3.1Type Annotation and Binding Forms

3.1.1Annotating Definitions

3.1.2Annotating Local Binding

3.1.3Annotating Functions

3.1.4Annotating Single Variables

3.1.5Annotating Expressions

3.2Type Inference

3.2.1When do you need type annotations?

3.3New Type Names

4Types in Typed Racket

4.2Function Types

4.3Types for Functions with Optional or Keyword Arguments

4.5Recursive Types

4.6Structure Types

4.7Types for Structure Type Properties

4.9Polymorphism

4.9.1Type Constructors

4.9.2Polymorphic Data Structures

4.9.3Polymorphic Functions

4.9.4Lexically Scoped Type Variables

4.10Variable-Arity Functions: Programming with Rest Arguments

4.10.1Uniform Variable-Arity Functions

4.10.2Non-Uniform Variable-Arity Functions

5Occurrence Typing

5.1Basic Occurrence Typing

5.2Propositions and Predicates

5.2.1Specifying Propositions

5.2.2One-sided Propositions

5.3Other conditionals and assertions

5.4A caveat about set!

5.5Access to structure fields

5.6let-aliasing

6Typed-Untyped Interaction

6.1Using Untyped Code in Typed Code

6.1.1Opaque Types

6.2Using Typed Code in Untyped Code

6.3Protecting Typed-Untyped Interaction

6.3.1Deep Types: Completely Reliable

6.3.2Shallow Types: Sound Types, Low-Cost Interactions

6.3.3Optional Types: It’s Just Racket

6.3.4When to Use Deep, Shallow, or Optional?

7Optimization in Typed Racket

7.1Turning the optimizer off

7.2Getting the most out of the optimizer

7.2.1Numeric types

7.2.4Contract boundaries

8Caveats and Limitations

8.1The Integer type and integer?

8.2Type inference for polymorphic functions

8.3Typed-untyped interaction and contract generation

8.4Unsupported features

8.5Type generalization

8.6Macros and compile-time computation

8.7Expensive contract boundaries

8.8Pattern Matching and Occurrence Typing

8.9is-a? and Occurrence Typing

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