Parameters

A parameter takes zero or one arguments. If called with no arguments, it returns the current value of the parameter. If called with one argument, it sets the parameter's value to that of the argument and returns the new value.

The following list of parameters does not yet include the compiler switches, which are also parameters.

Parameter break-handler

Parameter console-input-port-factory

Parameter console-output-port-factory

Parameter current-input-port

Parameter current-output-port

Parameter error-handler

Parameter evaluator

Parameter herald

Parameter interaction-environment

Parameter keyboard-interrupt-handler

Parameter load-evaluator

Parameter quit-handler

Parameter repl-level

Parameter repl-evaluator

Parameter repl-printer

Parameter reset-handler

Parameter standard-timeslice

Parameter structure-comparator

Parameter structure-printer

Parameter timer-interrupt-handler

Procedure make-parameter

(make-parameter name value [predicate]) => procedure

Create a parameter with name name, initial value value, and optional setter predicate predicate. When the parameter is set the new value is first passed to predicate,, and if it returns #F then an error is signalled. Name can be a symbol or a string.

Syntax parameterize

(parameterize ((parameter0 value0) ...) expr0 expr1 ...)

Parameterize overrides the values of a set of parameters in a dynamic scope -- it is like fluid-let for parameters.