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Parameters

A parameter is a thread-specific setting, such a the current output port or the current directory for resolving relative pathnames. A parameter procedure sets and retrieves the value of a specific parameter. For example, the current-output-port parameter procedure sets and retrieves a port value that is used by display when a specific output port is not provided. Applying a parameter procedure without an argument obtains the current value of a parameter in the current thread, and applying a parameter procedure to a single argument sets the parameter's value in the current thread (and returns void). For example, (current-output-port) returns the current default output port, while (current-output-port p) sets the default output port to p.





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