17.3 Interactive Help

► |  | Reference: Racket

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

▼ | 17 | Running Racket

17.1 | Running Racket or GRacket
17.2 | Libraries and Collections
17.3 | Interactive Help
17.4 | Interactive Module Loading
17.5 | Debugging

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#### 17.3`` Interactive Help

( require racket/help)

The bindings documented in this section are provided by the racket/help and racket/init libraries, which means that they are available when the Racket executable is started with no command-line arguments. They are not provided by racket/base or racket.

help

( help string ...)

( help id)

( help id #:from module-path)

( help #:search datum ...)

For general help, see the main documentation page.

The help form searches the documentation and opens a web browser (using the user’s selected browser) to display the results.

> > > See net/sendurl for information on how the user’s browser is launched to display help information.

A simple help or ( help) form opens the main documentation page.

The ( help string ...) form – using literal strings, as opposed to expressions that produce strings – performs a string-matching search. For example,

( help "web browser" "firefox")

searches the documentation index for references that include the phrase “web browser” or “firefox.”

A ( help id) form looks for documentation specific to the current binding of id. For example,

( require net/url)
( help url->string)

opens a web browser to show the documentation for url->string from the net/url library.

For the purposes of help, a for-label require introduces a binding without actually executing the net/url library – for cases when you want to check documentation, but cannot or do not want to run the providing module.

( require racket/gui) ; does not work in racket
( require ( for-label racket/gui)) ; ok in racket
( help frame%)

If id has no for-label and normal binding, then help lists all libraries that are known to export a binding for id.

The ( help id #:from module-path) variant is similar to ( help id), but using only the exports of module-path. (The module-path module is required for-label in a temporary namespace.)

( help frame% #:from racket/gui) ; equivalent to the above

The ( help #:search datum ...) form is similar to ( help string ...), where any non-string form of datum is converted to a string using display. No datum is evaluated as an expression.

For example,

( help #:search "web browser" firefox)

also searches the documentation index for references that include the phrase “web browser” or “firefox.”

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