Scheme 48 Manual | Contents | In Chapter: User's guide
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## Library

A number of useful utilities are either built in to Scheme 48 or can be loaded from an external library. These utilities are not visible in the user environment by default, but can be made available with the `open` command. For example, to use the `tables` structure, do

>     > ,open tables
>     >

If the utility is not already loaded, then the `,open` command will load it. Or, you can load something explicitly (without opening it) using the `load-package` command:

>     > ,load-package queues
>     > ,open queues

When loading a utility, the message "Note: optional optimizer not invoked" is innocuous. Feel free to ignore it.

See also the package system documentation, in the module chapter.

Not all of the the libraries available in Scheme 48 are described in this manual. All are listed in files `rts-packages.scm`, `comp-packages.scm`, `env-packages.scm`, and `more-packages.scm` in the `scheme` directory of the distribution, and the bindings they export are listed in `interfaces.scm` and `more-interfaces.scm` in the same directory.

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