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package main

import (
	"flag"
	"fmt"
	"strings"
)

const DB_REDSHIFT = "redshift"
const DB_POSTGRES = "postgres"

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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,

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⇐ back to the gist-blog at jrw.fi

Advanced SCSS

Or, 16 cool things you may not have known your stylesheets could do. I'd rather have kept it to a nice round number like 10, but they just kept coming. Sorry.

I've been using SCSS/SASS for most of my styling work since 2009, and I'm a huge fan of Compass (by the great @chriseppstein). It really helped many of us through the darkest cross-browser crap. Even though browsers are increasingly playing nice with CSS, another problem has become very topical: managing the complexity in stylesheets as our in-browser apps get larger and larger. SCSS is an indispensable tool for dealing with this.

This isn't an introduction to the language by a long shot; many things probably won't make sense unless you have some SCSS under your belt already. That said, if you're not yet comfy with the basics, check out the aweso

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public struct Credentials {
    
    public init(key: String, secret: String) {
        self.key = key
        self.secret = secret
    }
    
    public let key: String
    public let secret: String
}

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FILE SPACING:

 # double space a file
 sed G

 # double space a file which already has blank lines in it. Output file
 # should contain no more than one blank line between lines of text.
 sed '/^$/d;G'

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//
//  SimpleScrollingStack.swift
//  A super-simple demo of a scrolling UIStackView in iOS 9
//
//  Created by Paul Hudson on 10/06/2015.
//  Learn Swift at www.hackingwithswift.com
//  @twostraws
//

import UIKit

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function retry(isDone, next) {
    var current_trial = 0, max_retry = 50, interval = 10, is_timeout = false;
    var id = window.setInterval(
        function() {
            if (isDone()) {
                window.clearInterval(id);
                next(is_timeout);
            }
            if (current_trial++ > max_retry) {
                window.clearInterval(id);

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import Foundation
import SceneKit

class Icosahedron : Geometry {
    // The golden ratio
    static let t = (1.0 + sqrt(5.0)) / 2.0;
    
    // These vertices represent three orthogonal rectangles
    // The corners of which define the 12 vertices of an icosahedron
    // We get the normalized vector so that our points are on the unit sphere

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import UIKit

// Returns a list of points on the convex hull in counter-clockwise order.
// Note: the last point in the returned list is the same as the first one.
//
// https://en.wikibooks.org/wiki/Algorithm_Implementation/Geometry/Convex_hull/Monotone_chain
//
func closedConvexHull(points_ : [CGPoint]) -> [CGPoint] {
    
    // 2D cross product of OA and OB vectors, i.e. z-component of their 3D cross product.