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gui-available?
gui-dynamic-require

10 Dynamic Loading

The racket/gui/dynamic library provides functions for dynamically accessing the racket/gui/base library, instead of directly requiring racket/gui or racket/gui/base.

Returns #t if dynamic access to the GUI bindings is available. The bindings are available if racket/gui/base has been loaded, instantiated, and attached to the namespace in which racket/gui/dynamic was instantiated.

(gui-dynamic-require sym)  any
  sym : symbol?
Like dynamic-require, but specifically to access exports of racket/gui/base.