Full source: https://gist.github.com/mrange/aa9e0898492b6d384dd839bc4a2f96a1
Option<_> is great for ROP (Railway Oriented Programming) but we get no info on what went wrong (the failure value is None which carries no info).
With the introduction F# 4.1 we got Result<_, _> a "smarter" Option<_> as it allows us to pass a failure value.
However, when one inspects the signature of Result.bind one sees a potential issue for ROP:
| package main | |
| import ( | |
| "io/ioutil" | |
| "log" | |
| "os" | |
| "os/user" | |
| "strconv" | |
| ) |
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,
| // General hints on defining types with constraints or invariants | |
| // | |
| // Just as in C#, use a private constructor | |
| // and expose "factory" methods that enforce the constraints | |
| // | |
| // In F#, only classes can have private constructors with public members. | |
| // | |
| // If you want to use the record and DU types, the whole type becomes | |
| // private, which means that you also need to provide: | |
| // * a constructor function ("create"). |
2015-01-29 Unofficial Relay FAQ
Compilation of questions and answers about Relay from React.js Conf.
Disclaimer: I work on Relay at Facebook. Relay is a complex system on which we're iterating aggressively. I'll do my best here to provide accurate, useful answers, but the details are subject to change. I may also be wrong. Feedback and additional questions are welcome.
Relay is a new framework from Facebook that provides data-fetching functionality for React applications. It was announced at React.js Conf (January 2015).
| (ns user) | |
| (def app | |
| "Intenal Helper" | |
| (fnil conj [])) | |
| (defprotocol PathSeq | |
| (path-seq* [form path] "Helper for path-seq")) | |
| (extend-protocol PathSeq |
| module DapperFSharp = | |
| open System.Data.SqlClient | |
| open System.Dynamic | |
| open System.Collections.Generic | |
| open Dapper | |
| let dapperQuery<'Result> (query:string) (connection:SqlConnection) = | |
| connection.Query<'Result>(query) | |
| let dapperParametrizedQuery<'Result> (query:string) (param:obj) (connection:SqlConnection) : 'Result seq = |
| (* | |
| http://zoesmith.io | |
| Export Bookmarks from Evernote to Pinboard | |
| v1.4 12th September 2012 | |
| This script takes selected notes in Evernote and sends an email for each to Pinboard, extracting each note's title, source URL and associated tags. The user should enter their Pinboard email address in the pinboardEmail property below, and can choose a default tag to add to each bookmark on import. | |
| This code is hacky, horrible and non-error checking (but it worked for me). Don't use on thousands of notes at a time, it'll go all crashy. Try selecting one test note first to see if it works for you. | |
| Change log: |
| i386 : iPhone Simulator | |
| x86_64 : iPhone Simulator | |
| arm64 : iPhone Simulator | |
| iPhone1,1 : iPhone | |
| iPhone1,2 : iPhone 3G | |
| iPhone2,1 : iPhone 3GS | |
| iPhone3,1 : iPhone 4 | |
| iPhone3,2 : iPhone 4 GSM Rev A | |
| iPhone3,3 : iPhone 4 CDMA | |
| iPhone4,1 : iPhone 4S |
| ּ_בּ | |
| בּ_בּ | |
| טּ_טּ | |
| כּ‗כּ | |
| לּ_לּ | |
| מּ_מּ | |
| סּ_סּ | |
| תּ_תּ | |
| ٩(×̯×)۶ | |
| ٩(̾●̮̮̃̾•̃̾)۶ |
