The sgl/gl library provides direct access to the C-style OpenGL API, whereas the sgl library provides a more Racket-like interface. The sgl/gl library provides a binding for each #defined constant and for most functions in OpenGL 1.5 and GLU 1.3. The functions perform comparable checking to their C-language counterparts; they check the types of their arguments, but do not check the length of array arguments. The sgl library provides wrappers around many of the functions in the sgl/gl library to present a more Racket-friendly interface, including function names that follow Racket conventions, and checked, symbolic enumeration arguments, and array-length checks.
Warning on Safety: OpenGL programming is inherently unsafe, even when using only the sgl library. Although sgl checks the arguments to each function call, violation of higher-level assumptions of the system’s OpenGL library can cause it to crash, bringing the entire Racket system down. For example, sending a large number of vertices in a single glBegin causes at least some GL implementations to crash.
Some examples are available in the "examples" directory of the "sgl" collection in the Racket installation. For "alpha.rkt", try choosing the "sk.jpg" image distritbuted with Racket in the "icons" collection; you may have to press the t key a few times if the spinning cube is blank.