18.3 Interactive Help
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.”