make-parameter

(make-parameter value), (make-parameter value converter)

Answers a parameter object: a procedure of no arguments answering its current value. That value is value, or (converter value) when a converter is given, until a parameterize binds another. procedure? of a parameter object is #t. A thread started by parallel-execute starts with the caller's values.

Deviation: calling a parameter object with an argument is an error; Gauche sets its value.