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