Block Computed Property Design Pattern. Defines a type of struct and initializes an instance that passes a pointer to the instance to its block member.

struct_type_default_initializer.h

typedef struct __attribute__((objc_boxable)) ArcDegreesMeasurements ArcDegreesMeasurements;
typedef NSUInteger (^(^ArcDegreesMeasurementsEnd)(void))(void);
struct __attribute__((objc_boxable)) ArcDegreesMeasurements
{
    NSUInteger start;
    NSUInteger length;
    __unsafe_unretained ArcDegreesMeasurementsEnd end;
    NSUInteger sectors;
} arcDegreesMeasurements = {
    .start = 0,
    .length = 360,
    .end = ^ {
        return ^ (ArcDegreesMeasurements * arc_degree_measurements) {
            return ^ NSUInteger (void) {
                return (NSUInteger)radiansToDegrees(degreesToRadians(arc_degree_measurements->start + arc_degree_measurements->length));
            };
        }(&arcDegreesMeasurements);
    }
};

// To access the value of the computed property: arcDegreesMeasurements.end()()