Real World Haskell
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A couple months ago at last I decided to learn Haskell. It's quite a cool language, but I'm puzzled about how an event driven real app would be programmed in such a language. Do you know of a good tutorial about it
Note: When I say \"real app\" I'm not talking of a real world, production ready app. I just mean a little sample app, just to get the grasp of it. I think something like a simplified version of the windows caculator would be great, and then perhaps something a bit more complex.
A lot of times (I'm not saying that this is the case in your question, but it is a recurring pattern) when someone says \"but can Haskell be used in the real world\", what they are really saying is \"I know how to do this in C, and in Haskell I cannot do it in exactly the same way, therefore it must be impossible in Haskell, therefore Haskell is not ready for the real world\". But what they are missing out on, is that there might be a totally different and much better way to solve the problem. (It's like saying \"Erlang doesn't have threads, therefore it cannot possibly be used to implement concurrent systems.\") And FRP is just one example.
you should check out Real World Haskell. The book is freely available and shows how Haskell can be applied to real world problems. I wouldn't call it a tutorial, tho, as it is much more comprehensive.
It's old. RWH was written at a time version 6.8 of GHC was being used. 6.8 used base version 3.0.x.x. 6.10.1 already used 184.108.40.206, which introduced many changes. And that's just the jump from 6.8 to 6.10. The current version of GHC is 7.10. Monads have been changed. There's currently a discussion to remove return from Monad, so the Monad instance in Real World Haskell will really be out of sync with the real world.
Something you can read along while reading RWH is \"What I Wish I Knew When Learning Haskell\" by Stephen Diehl. It provides additional insight, but be aware, some sections aren't really newcomer friendly.
GHC 6.8 was the last version before the Haskell Platform has been introduced. Therefore, the appendix tells you to get GHC and Cabal by hand. Don't. Instead, follow the instructions on the haskell.org download page.
Beta Books: What do I get Haskell is a pure functional programming language with a rich ecosystemof tools and libraries. Designed to push the boundaries of programming,it offers unparalleled power for building reliable and maintainablesystems. But to unleash that power, you need a guide. Effective Haskellis that guide. Written by an engineer who understands how to applyHaskell to the real world and uses it daily to get practical work done,it is your ticket to Haskell mastery.
Gain deep understanding of how Haskell deals with IO and the outsideworld by writing a complete Haskell application that does severaldifferent kinds of IO. Reinforce your learnings with practice exercisesin every chapter.
This easy-to-use, fast-moving tutorial introduces you to functional programming with Haskell. You'll learn how to use Haskell in a variety of practical ways, from short scripts to large and demanding applications. Real World Haskell takes you through the basics of functional programming at a brisk pace, and then helps you increase your understanding of Haskell in real-world issues like I/O, performance, dealing with data, concurrency, and more as you move through each chapter.
John Goerzen is an American hacker and author. He has written a number of real-world Haskell libraries and applications, including the HDBC database interface, the ConfigFile configuration file interface, a podcast downloader, and various other libraries relating to networks, parsing, logging, and POSIX code. John has been a developer for the Debian GNU/Linux operating system project for over 10 years and maintains numerous Haskell libraries and code for Debian. He also served as President of Software in the Public Interest, Inc., the legal parent organization of Debian. John lives in rural Kansas with his wife and son, where he enjoys photography and geocaching.
Don Stewart is an Australian hacker based in Portland, Oregon. Don has been involved in a diverse range of Haskell projects, including practical libraries, such as Data.ByteString and Data.Binary, as well as applying the Haskell philosophy to real-world applications including compilers, linkers, text editors, network servers, and systems software. His recent work has focused on optimizing Haskell for high-performance scenarios, using techniques from term rewriting.
It is clear that The Three wanted to bring this phenomenal langauge tomainstream industry in order to save themselves (and the rest of the world) fromthe toil of working with non-functional programming languages.
In order to use Haskell locally, we have to install it first. I will not go into the details of that now. Just follow the links on the resources page. There are plenty of competing installation instructions out there in the world. I do not particularly care which one you follow, but make sure you get GHC-7.10.3.
We will work with String for now, but just for reference: There are two String-like data types out there that you would reach out to in real code: Text and ByteString. The former handles Unicode text, and should be used for, well text. The latter handles packed arrays of bytes, and should be used for binary data. Mixing up strings and binary data is another major cause of bugs in any programming languge, and again the distinction here helps.
No real surprises here. We create the heap object, push the address of the newly created heap object onto the stack, and call want_Int_info. The same happens when we call want_Double, except of course that we need to create a larger heap object (12 bytes rather than 8).
with two arguments is thought of as a function of a single argument of type Int#, which returns a new function, that takes an argument of type Double# and returns an Int#. The compiler does not implement that literally, however, as that would be much too slow. Instead, a function such as want_ID## really does take two arguments, both of which are on the stack (or in registers on architectures where that is possible); want_ID## gets compiled to
This is really no different from supplying just one argument; we still have to deal with the same set of possibilities; the only difference is that we now need a payload for two pointers. This is created by stg_ap_pp_fast:
For now, if this really matters it is faster to use a single Proxy# argument, and make sure that it is the last argument so that we can take advantage of the specialized stg_ap functions which were introduced for the IO monad:
Description:Real World Haskell takes you through the basics of functional programming at a brisk pace, and then helps you increase your understanding of Haskell in real-world issues like I/O, performance, dealing with data, concurrency, and more as you move through each chapter. With this book, you will: Understand the differences between procedural and functional programming; Learn the features of Haskell, and how to use it to develop useful programs; Interact with filesystems, databases, and network services; Write solid code with automated tests, code coverage, and error handling; Harness the power of multicore systems via concurrent and parallel programming.
The Semantic project is concerned with parsing, analyzing (evaluating), and comparing source code and as such we are firmly rooted in the academic domain of programming language theory (PLT) and spend significant time applying existing research to the real world problem of analyzing source code on GitHub. Haskell is well suited to this domain. Its language features allow concise, correct, and elegant expression of the data structures and algorithms we work with. (Source)
At the same time, new programming languages like Rust and TypeScript have taken the world of general software development by storm. They incorporate a lot of what is good about Haskell (and FP in general) while also focusing on great developer experience and being more approachable.
In this fast-moving, interactive tutorial we will learn Haskell by developing a realistic analytic application: we'll crawl a web site and rank its pages in order of authority. This combines some very modern concerns: network programming; handling dodgy HTML; big data; and number crunching. With our emphasis on getting real work done, we'll show off some of Haskell's compelling features and demonstrate how they help us to develop dependable, easy to understand code.
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