Language

• (compile-allow-cond-fallthrough [on?]) gets or sets a Boolean value indicating how to compile a cond or case expression without an else clause. If the value of this parameter is a true value, then cond or case expressions are compiled so that void is returned if no clause matches. Otherwise, cond or case expressions are compiled to raise the exn:else exception when no clause matches. Note that this parameter is used when an expression is compiled, not when it is evaluated.
• (compile-allow-set!-undefined [on?]) gets or sets a Boolean value indicating how to compile a set! expression that mutates a global variable. If the value of this parameter is a true value, set! expressions for global variables are compiled so that the global variable is set even if it was not previously defined. Otherwise, set! expressions for global variables are compiled to raise the exn:variable exception if the global variable is not defined at the time the set! is performed. Note that this parameter is used when an expression is compiled, not when it is evaluated.