Tutorial by Examples: re

Given data Empty a we have data Free Empty a = Pure a -- the Free constructor is impossible! which is isomorphic to data Identity a = Identity a

Given data Identity a = Identity a we have data Free Identity a = Pure a | Free (Identity (Free Identity a)) which is isomorphic to data Deferred a = Now a | Later (Deferred a) or equivalently (if you promise to evaluate the fst element first) (Nat, a), aka Writer...

Given data Maybe a = Just a | Nothing we have data Free Maybe a = Pure a | Free (Just (Free Maybe a)) | Free Nothing which is equivalent to data Hopes a = Confirmed a | Possible (Hopes a) | Failed or equivalently (if you promise to evalua...

Given data Writer w a = Writer w a we have data Free (Writer w) a = Pure a | Free (Writer w (Free (Writer w) a)) which is isomorphic to data ProgLog w a = Done a | After w (ProgLog w a) or, equivalently, (if you promise to evaluate the log first), Writer [w] a. ...

Given data Const c a = Const c we have data Free (Const c) a = Pure a | Free (Const c) which is isomorphic to data Either c a = Right a | Left c

Given data Reader x a = Reader (x -> a) we have data Free (Reader x) a = Pure a | Free (x -> Free (Reader x) a) which is isomorphic to data Demand x a = Satisfied a | Hungry (x -> Demand x a) or equivalently Stream x -> a with data Stream x = Stream x...

Given data Empty a we have data Cofree Empty a -- = a :< ... not possible!

Given data Const c a = Const c we have data Cofree (Const c) a = a :< Const c which is isomorphic to data Writer c a = Writer c a

Given data Identity a = Identity a we have data Cofree Identity a = a :< Identity (Cofree Identity a) which is isomorphic to data Stream a = Stream a (Stream a)

Given data Maybe a = Just a | Nothing we have data Cofree Maybe a = a :< Just (Cofree Maybe a) | a :< Nothing which is isomorphic to data NonEmpty a = NECons a (NonEmpty a) | NESingle a

Given data Writer w a = Writer w a we have data Cofree (Writer w) a = a :< (w, Cofree (Writer w) a) which is equivalent to data Stream (w,a) = Stream (w,a) (Stream (w,a)) which can properly be written as WriterT w Stream with data WriterT w m a = WriterT (m (w,a))

Given data Either e a = Left e | Right a we have data Cofree (Either e) a = a :< Left e | a :< Right (Cofree (Either e) a) which is isomorphic to data Hospitable e a = Sorry_AllIHaveIsThis_Here'sWhy a e | EatThis a (Hospitable e a) or, if yo...

Given data Reader x a = Reader (x -> a) we have data Cofree (Reader x) a = a :< (x -> Cofree (Reader x) a) which is isomorphic to data Plant x a = Plant a (x -> Plant x a) aka Moore machine.

Xcode have ability to run any script with hotkey. Here is example how to assign hotkey ⌘+⌥+⌃+⇧+T to open Terminal app in current project folder. Create bash script and save it in some folder #!/bin/bash # Project Name: $XcodeProject # Project Dir: $XcodeProjectPath # Workspace Dir: $X...

Debugging takes time and effort. Instead of chasing bugs with a debugger, consider spending more time on making your code better by: Write and run Tests. Python and Django have great builtin testing frameworks - that can be used to test your code much faster than manually with a debugger. Writ...

To display current version, we can use VERSION from @angular/core package. import { Component, VERSION } from '@angular/core'; @Component({ selector: 'my-app', template: `<h1>Hello {{name}}</h1> <h2>Current Version: {{ver}}</h2> `, }) export class AppCompone...

Binary Literals: The integral types (byte, short, int, and long) can also be expressed using the binary number system. To specify a binary literal, add the prefix 0b or 0B to the number. Strings in switch Statements: You can use a String object in the expression of a switch statement The try-wit...

Lambda Expressions, a new language feature, has been introduced in this release. They enable you to treat functionality as a method argument, or code as data. Lambda expressions let you express instances of single-method interfaces (referred to as functional interfaces) more compactly. Method r...

If you want to investigate why you are maxing out your DTUs, add other metrics to the performance graph to see which metric is dominiationg your DTU usage. In this example, the DTU usage is clearly dominiated by the CPU usage

A common usecase is to discard certain rest-calls, that are not needed any more after certain user-inputs. The most prominent example would be, when a user uses some search-function, makes a request, makes another request and for some reason the first request arrives after the second request and the...