► |  | The Racket Reference

1 | Language Model
2 | Notation for Documentation
3 | Syntactic Forms
4 | Datatypes
5 | Structures
6 | Classes and Objects
7 | Units
8 | Contracts
9 | Pattern Matching
10 | Control Flow
11 | Concurrency and Parallelism
12 | Macros
13 | Input and Output
14 | Reflection and Security
15 | Operating System
16 | Memory Management
17 | Unsafe Operations
18 | Running Racket
| Bibliography
| Index

▼ | 3 | Syntactic Forms

3.1 | Modules: module, module*, ...
3.2 | Importing and Exporting: require and provide
3.3 | Literals: quote and #%datum
3.4 | Expression Wrapper: #%expression
3.5 | Variable References and #%top
3.6 | Locations: #%variable-reference
3.7 | Procedure Applications and #%app
3.8 | Procedure Expressions: lambda and case-lambda
3.9 | Local Binding: let, let*, letrec, ...
3.10 | Local Definitions: local
3.11 | Constructing Graphs: shared
3.12 | Conditionals: if, cond, and, and or
3.13 | Dispatch: case
3.14 | Definitions: define, define-syntax, ...
3.15 | Sequencing: begin, begin0, and begin-for-syntax
3.16 | Guarded Evaluation: when and unless
3.17 | Assignment: set! and set!-values
3.18 | Iterations and Comprehensions: for, for/ list, ...
3.19 | Continuation Marks: with-continuation-mark
3.20 | Quasiquoting: quasiquote, unquote, and unquote-splicing
3.21 | Syntax Quoting: quote-syntax
3.22 | Interaction Wrapper: #%top-interaction
3.23 | Blocks: block
3.24 | Internal-Definition Limiting: #%stratified-body
3.25 | Performance Hints: begin-encourage-inline
3.26 | Importing Modules Lazily: lazy-require

On this page:

lazy-require

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#### 3.26`` Importing Modules Lazily: lazy-require

(require racket/lazy-require) | package: base

The bindings documented in this section are provided by the racket/lazy-require library, not racket/base or racket.

> syntax (lazy-require [module-path (fun-import ...)] ...)
> fun-import |  | = |  | fun-id
> |  | | |  | (orig-fun-id fun-id)

Defines each fun-id as a function that, when called, dynamically requires the export named orig-fun-id from the module specified by module-path and calls it with the same arguments. If orig-fun-id is not given, it defaults to fun-id.

If the enclosing relative phase level is not 0, then module-path is also placed in a submodule (with a use of define-runtime-module-path-index at phase level 0 within the submodule). Introduced submodules have the names lazy-require-n-m, where n is a phase-level number and m is a number.

When the use of a lazily-required function triggers module loading, it also triggers a use of register-external-module to declare an indirect compilation dependency (in case the function is used in the process of compiling a module).

Examples:

> > (lazy-require
> [racket/list (partition)])
> > (partition even? '(1 2 3 4 5))
> '(2 4)
> '(1 3 5)
> > (module hello racket/base
> (provide hello)
> (printf "starting hello server\n")
> (define (hello) (printf "hello!\n")))
> > (lazy-require
> ['hello ([hello greet])])
> > (greet)
> starting hello server
> hello!

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