scheme - define-type returning error on DrScheme -
When I try to run a defined type on the dosim, I get an error for an identifier "before its definition" Is: defined-type ". Why is this happening?
I input:
(defined type GUI [label (text string?)] [Button (text string?) (Enabled? Boolean?)]
and returns to me:
Before its definition, reference to an identifier: defined-type
Defined-type is not part of the "basic" plan, it is a part of "typed scheme." To use this language in the DR scheme To:
Ensure that "modi In the bottom window, enter:
#lang type-scheme
and "run" in the bottom left of the window. "Press the button.
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