mikeash

func effIt<Target, Result>(_ keypath: KeyPath<Target, Result>) -> (Target) -> Result {
    return { $0[keyPath: keypath] }
}

struct Foo {
    var x: Int
    var y: Int
}

mikeash

#import <Foundation/Foundation.h>

int main(int argc, char **argv) {
  auto global = ^{ NSLog(@"Hello, world!"); };
  auto captures = ^{ NSLog(@"argc is %d", argc); };
  NSLog(@"global: %@ -  captures: %@", global, captures);
  NSLog(@"(void *)global: %p -  (void *)captures: %p", (void *)global, (void *)captures);
  
  id globalCopy = [global copy];
  id capturesCopy = [captures copy];

mikeash

func ??<T>(lhs: T?, rhs: @autoclosure () throws -> Never) rethrows -> T {
  guard let value = lhs else { try rhs() }
  return value
}

func ??<T>(lhs: T?, rhs: () throws -> Never) rethrows -> T {
  guard let value = lhs else { try rhs() }
  return value
}

mikeash

#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
  Dl_info info;
  int success = dladdr(main, &info);
  if (success == 0) abort();
  printf("main is at %p and the mach-o header that contains it is at %p\n", main, info.dli_fbase);
}

mikeash

class C {}

protocol P where Self: C {
  var x: Int { get }
  var y: Int { get }
}

extension P {
  var x: Int { return 42 }
}

mikeash

#include <iostream>
#include <functional>

using namespace std;

void f(std::function<void(int)> call) {
    call(1);
    call(2);
    call(3);
}

mikeash

@import Foundation;
@import ObjectiveC;


static NSMutableSet *swizzledClasses;
static NSMutableDictionary *swizzledBlocks; // Class -> SEL (as string) -> block
static IMP forwardingIMP;
static dispatch_once_t once;

void Swizzle(Class c, SEL sel, void (^block)(NSInvocation *)) {

mikeash

extension Optional: Sequence {
    public func makeIterator() -> Iterator {
        return Iterator(optional: self)
    }
    
    public struct Iterator: IteratorProtocol {
        var optional: Wrapped?
        
        public mutating func next() -> Wrapped? {
            defer { optional = nil }

mikeash

let ptr = {}
func -<T>(lhs: T?, rhs: () -> Void) -> T? {
    return nil
}

var d: [String: String] = [:]
d["one"] = "won"
d["two"] = "too"
d["one"] = nil-ptr
d["two"] = nil-ptr

mikeash

import Foundation

func machToNanoseconds(_ mach: UInt64) -> Double {
    struct Static {
        static var info: mach_timebase_info = {
            var info = mach_timebase_info()
            mach_timebase_info(&info)
            return info
        }()
    }