ilyaigpetrov

Client/Server Data Synchronization

Open Source

• Redis
  In-memory db with notifications, may be used alongside other DB.
• Meteor
  • MongoDB | Livequery | server DDP | DDP client | minimongo
  • Livequery for DB updates subscriptions (MongoDB)
  • Minimongo is MongoDB imitation, used for latency compenstion.

• Opinionated, heavy, not very modular.

hsurreal

with
    dau as (
        -- This part of the query can be pretty much anything.
        -- The only requirement is that it have three columns:
        --   dt, user_id, inc_amt
        -- Where dt is a date and user_id is some unique identifier for a user.
        -- Each dt-user_id pair should be unique in this table.
        -- inc_amt represents the amount of value that this user created on dt.
        -- The most common case is
        --   inc_amt = incremental revenue from the user on dt

Catfish-Man

#!/usr/sbin/dtrace -q -s

/*
set(char *key, char *domain, char *user, char *host, char *container, char *value)
*/
CFPreferences$target:::set {
   printf("Set request at %Y ( key: %s, domain: %s, user:%s, host: %s, container: %s, value: %s)\n", walltimestamp, copyinstr(arg0), copyinstr(arg1), copyinstr(arg2), copyinstr(arg3), copyinstr(arg4), copyinstr(arg5));
   ustack();
   printf("\n\n\n");
}

jspahrsummers

#import <Foundation/Foundation.h>

int main (int argc, const char **argv) {
  @autoreleasepool {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
      dispatch_sync(dispatch_get_main_queue(), ^{
        NSLog(@"is main thread? %i", (int)[NSThread isMainThread]);
      });
    });

NachoSoto

//
//  Signal+Extensions.swift
//  Khan Academy
//
//  Created by Nacho Soto on 10/1/15.
//  Copyright © 2015 Khan Academy. All rights reserved.
//

import ReactiveCocoa

Catfish-Man

// Compile with clang -framework Foundation sethack.m

#import <Foundation/Foundation.h>
#import <objc/runtime.h>

/*
 CFHashBytes from http://www.opensource.apple.com/source/CF/CF-1153.18/CFUtilities.c
 */
#define ELF_STEP(B) T1 = (H << 4) + B; T2 = T1 & 0xF0000000; if (T2) T1 ^= (T2 >> 24); T1 &= (~T2); H = T1;

andymatuschak

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

JadenGeller

/* -fno-objc-arc
 CFTypeRef _unsafeCreatePartiallyInitialized(Class c) {
 Method method = class_getInstanceMethod([NSObject class], @selector(init));
 IMP imp = method_getImplementation(method);
 return ((id (*)(id, SEL))imp)([c alloc], @selector(init));
 }

 void _unsafeDestructPartiallyInitialized(CFTypeRef x) {
 Method method = class_getInstanceMethod([NSObject class], @selector(dealloc));
 IMP imp = method_getImplementation(method);

jspahrsummers

template<typename Left, typename Right>
struct Intersect
{
  // This will fail to compile if there's no specialization for Intersect<Right, Left>,
  // thereby verifying that we've handled all combinations.
  typename Intersect<Right, Left>::Result operator() (const Left &lhs, const Right &rhs) const
  {
    return Intersect<Right, Left>()(rhs, lhs);
  }
};

russbishop

// If you want types initializable from String literals
// but don't want to implement three separate initializers.


extension ExpressibleByUnicodeScalarLiteral where Self: ExpressibleByStringLiteral, Self.StringLiteralType == String {
    public init(unicodeScalarLiteral value: String) {
        self.init(stringLiteral: value)
    }
}