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.”