Syntax in Functions - Learn You a Haskell for Great Good!Whereas patterns are a way of making sure a value conforms to some form and
deconstructing it, guards are a way of testing whether some property of a value ...

Learn You a Haskell for Great Good!Hey yo! This is Learn You a Haskell , the funkiest way to learn Haskell, which is
the best functional programming language around. You may have heard of it. Table of contentsIntroduction - Starting Out - Syntax in Functions - Input and OutputIntroductionIntroduction. About this tutorial. Welcome to Learn You a

Starting Out - Learn You a Haskell for Great Good!For a start, we'll try calling one of the most boring functions in Haskell . ghci> succ
8 ..... List comprehensions are very similar to set comprehensions. We'll stick to ...

Hey yo! This is Learn You a Haskell , the funkiest way to learn Haskell , which is
the best functional programming language around. You may have heard of it.

Higher Order Functions - Learn You a Haskell for Great Good!Higher order functions aren't just a part of the Haskell experience, they pretty
much are the

Chapters - Learn You a Haskell for Great Good !Learn You a Haskell for Great Good ! Introduction · About this tutorial · So what's
Haskell? What you need to dive in · Starting Out · Ready, set, go! Baby's first ...

When defining functions, you can define separate function bodies for different ....
Notice that if you want to bind to several variables (even if one of them is just _ ...

Types and Typeclasses - Learn You a Haskell for Great Good!We covered some of the basics of Haskell with only a very superficial glance at
types . However, understanding the type system is a very important part of ...

Introduction - Learn You a Haskell for Great Good!Welcome to Learn You a Haskell for Great Good! If you 're reading this, chances
are you want to learn Haskell. Well, you 've come to the right place, but let's talk ...

A Fistful of Monads - Learn You a Haskell for Great Good!And now, let's think about how we would do >>= for Maybe . Like we said, >>=
takes a monadic value, and a function that takes a normal value and returns a ...

Recursion - Learn You a Haskell for Great Good!We mention recursion briefly in the previous chapter. In this chapter, we'll take a
closer look at recursion , why it's important to Haskell and how we can work out ...

For a Few Monads More - Learn You a Haskell for Great Good !Exploring a few monads more will also solidify our intuition for monads. The
monads that we'll be exploring are all part of the mtl package. A Haskell package
is ...

For a Few Monads More - Learn You a Haskell for Great Good!We've also learned how to work in the IO monad, even before we knew what a
monad was! In this chapter, we're going to learn about a few other monads.

When defining functions , you can define separate function bodies for different ....
Here's how we would have done it if we didn't know about pattern matching:.

Functionally Solving Problems - Learn You a Haskell for Great Good!The downside to it is that we have to use parentheses to denote precedence.
Reverse Polish notation is another way of writing down mathematical
expressions.

Previously we mentioned that Haskell has a static type system. ... We didn't have
to give this function a type declaration because the compiler can infer by itself ...

When you do import Data . List , all the functions that Data . List exports become
available in the global namespace, meaning that you can call them from
wherever ...

Instead of explaining their syntax , let's just dive in and make a function using
guards. We're going to make a simple function that berates you differently ...

Types and Typeclasses - Learn You a Haskell for Great Good !If you write a program where you try to divide a boolean type with some number,
.... The type of those two values must be a member of the Eq class (this was the ...

In this chapter, we're going to learn about a few other monads. We'll see how they
can .... Here are a few more examples of using applyLog: ghci> ("Tobin","Got ...

Functors , Applicative Functors and Monoids - Learn You a Haskell In Haskell, they're described by the typeclass Functor , which has only one
typeclass ..... A function a -> b -> c actually takes just one parameter of type a and
then ...

While most modern calculators use infix notation, some people still swear by
RPN calculators . This is what the previous infix expression looks like in RPN: 10
4 3 ...

Here's how we would have done it if we didn't know about pattern matching: .....
where bindings aren't shared across function bodies of different patterns.

List module is all about lists , obviously. It provides some very useful functions for
dealing with them. We've already met some of its functions (like map and filter) ...

Using partial application ( calling functions with too few parameters, if you will) ....
map takes a function and a list and applies that function to every element in the ...

Every function in Haskell officially only takes one parameter . ..... map takes a
function and a list and applies that function to every element in the list, producing
a ...

FAQ - Learn You a Haskell for Great Good!There are loads of awesome tutorials out there, but I'd just like to point out how
great Real World Haskell is. It's really great. I feel it complements this tutorial ...

Hey yo! This is Learn You a Haskell, the funkiest way to learn Haskell, which is
the best functional programming language around. You may have heard of it.

Making Our Own Types and Typeclasses - Learn You a Haskell for In this chapter, we'll learn how to make our own and how to put them to work! ...
Let's see how the Bool type is defined in the standard library. data Bool = False |
...

Haskell functions can take functions as parameters and return functions as return
values. A function that does either of those is called a higher order function .

For a start, we'll try calling one of the most boring functions in Haskell . ghci> succ
8; 9 .... The first is that in the function name we didn't capitalize Conan's name.

In Haskell, lists are a homogenous data structure. It stores several elements of
the same type. That means that we can have a list of integers or a list of
characters ...

Previously we mentioned that Haskell has a static type system. The type of every
expression is known at compile time, which leads to safer code. If you write a ...

That's good because it's better to catch such errors at compile time instead of
having your program crash. .... What's the type signature of the == function?

In this chapter, we'll take a closer look at recursion, why it's important to Haskell
and how we can work ..... There's a very cool algoritm for sorting called quicksort .

Zippers - Learn You a Haskell for Great Good!So our tree is either empty or it's a node that has an element and two sub- trees .
...... from break as the focus and build a breadcrumb that has all the data it needs.

In the previous chapters, we covered some existing Haskell types and
typeclasses. In this chapter, we'll learn how to make our own and how to put them
to work!

However, understanding the type system is a very important part of learning
Haskell. A type is a kind of label that every expression has. It tells us in which ...

This tutorial is aimed at people who have experience in imperative programming
languages (C, C++, Java, Python …) but haven't programmed in a functional ...

The syntax for importing modules in a Haskell script is import < module name>. ...
Reading the source code of some modules is a really good way to learn ...

For instance, the fibonacci sequence is defined recursively. First, we define the
first two fibonacci numbers non-recursively. We say that F(0) = 0 and F(1) = 1, ...

And now, we want to sort them! There's a very cool algoritm for sorting called
quicksort . It's a very clever way of sorting items. While it takes upwards of 10 lines
to ...

is read as "has type of". ... So we read that as it being a list of characters. ..... We
do that by adding :: at the end of the expression and then specifying a type.

Introduction . About this tutorial. Welcome to Learn You a Haskell for Great Good!
If you're reading this, chances are you want to learn Haskell. Well, you've come ...

Chapters - Learn You a Haskell for Great Good!Learn You a Haskell for Great Good! Introduction · About this tutorial · So what's
Haskell ? What you need to dive in · Starting Out · Ready, set, go! Baby's first ...

lucky :: (Integral a) => a -> String; lucky 7 = " LUCKY NUMBER SEVEN! ... catch all
the numbers and they wouldn't have a chance to fall through and be checked ...

Syntax in Functions - Learn You a Haskell for Great Good !This chapter will cover some of Haskell's cool syntactic constructs and we'll .....
Guards are indicated by pipes that follow a function's name and its parameters.

Recursion is actually a way of defining functions in which the function is applied
... Let's take an example list of numbers and check out how this would work on ...

There's also a very clever way for zipping infinite numbers of lists , but we're not
..... Then we add the shift amount to each number before converting the list of ...

The Maybe Int is for how big the chunk should be, in bytes . If it's Nothing, then the
operating system determines the chunk size. NoBuffering means that it will be ...

For example, in C , you use parentheses to call functions like foo(), bar(1) or baz(3
, "haha"). Like we ..... If you want to get an element out of a list by index , use !

First , we get a line from the terminal by performing getLine call that line line . .... If
it's not empty, then print the first character of the string by doing putChar and ...

So far, we've run into a lot of data types . Bool, Int, Char, Maybe, etc. But how do
we make our own? Well, one way is to use the data keyword to define a type .

With those two parts separated, we can still reason about our pure program and
..... Note that due to buffering, reading of the characters won't actually happen ...

If we write a number , we don't have to tell Haskell it's a number . .... [a] -> Bool
because it uses == over a list to check whether some value we're looking for is in
it.

When defining functions, you can define separate function bodies for different
patterns. This leads to really neat code that's simple and readable. You can
pattern ...

List module, which has a bunch of useful functions for working with lists and use
a function that it exports to create a function that tells us how many unique ...

Yeah, I know it's not but bear with me. A little pitfall to watch out for here is
negating numbers. If we want to have a negative number, it's always best to
surround it ...

Higher order functions aren't just a part of the Haskell experience, they pretty
much are the Haskell experience. It turns out that if you want to define
computations ...

Starting Out. Ready , set , go ! egg Alright, let's get started! If you're the sort of
horrible person who doesn't read introductions to things and you skipped it, you ...

Like, what if we have Just (*3), how do we apply that to Just 5? What if we don't
want to apply it to Just 5 but to a Nothing instead? Or if we have [(*2),(+4)], how ...

This tutorial is aimed at people who have experience in imperative programming
languages (C, C++, Java, Python …) but haven't programmed in a functional ...

Our data type is good , although it could be better. Let's make an ...... Here's how
the standard library defines String as a synonym for [Char]. type String = [Char].

Learn You a Haskell for Great Good! Introduction · About this tutorial · So what's
Haskell? What you need to dive in · Starting Out · Ready, set, go! Baby's first ...

Modules - Learn You a Haskell for Great Good !The Haskell standard library is split into modules, each of them contains functions
and types that are somehow related and serve some common purpose.

Next up, 3 is used as the accumulator value and 5 as the current element and 8
..... meaning that composing two functions produces a new function that, when ...

Testing it out produces pretty predictable results (remember to append this
function ..... So if you're not in GHCI, it's better to split longer list comprehensions
across multiple ..... "grouchy pope","scheming hobo ","scheming frog","scheming
pope"].

When you call lucky , the patterns will be checked from top to bottom and when it
conforms to a ...... They can also be used to introduce functions in a local scope :.

Before we move on to files , let's take a look at some functions that are useful .....
We run the getContents I/O action and name the string it produces contents .

Here we see that doing :t on an expression prints out the expression followed by :
: and its type . .... Because it's not in capital case it's actually a type variable . ...
have names longer than one character, we usually give them names of a, b, c , d
…