The type of an Objective-C object, an opaque pointer.
The type of an Objective-C class, which is also an _id.
The type of an Objective-C selector, an opaque pointer.
The Objective-C boolean type. Scheme values are converted for C in the usual way: #f is false and any other value is true. C values are converted to Scheme booleans.
Synonym for #t
Synonym for #f