User:Lenny222/Haskell explained to the busy
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You have heard about Haskell but don't have the time to find out what it is?
This page may be for you.
Introduction
What is Haskell?
Haskell is a purely functional, lazy, statically typed programming language
What is a purely functional programming language?
What is good about that?
What is a lazy programming language?
What is good about that?
What is a statically typed programming language
What is good about that?
Is Haskell Open Source?
Why the name "Haskell"?
Haskell is named after the American mathematician Haskell Curry
Basics
| Question | Answer |
|---|---|
| What is the meaning of the double colon "::"? | TODO |
| What is the meaning of the square brackets "[" and "]"? | TODO |
| What is the meaning of the colon ":"? | ":" is an infix operator that adds an element to the beginning of a list
For example: 1 : [2,3]
will result in the new list [1,2,3]
|
| What is an infix operator? | Infix operators are normal functions. TODO: symbols, round brackets
For example: 5 + 2
is the same as (+) 5 2
|
| Are there any prefix operators? | TODO |
| What is the meaning of the backtick "`"? | A function enclosed in "`"s can be used as an infix operator.
For example: subtract 2 10
is the same as 2 `subtract` 10
|
| What is the meaning of the tick " ' "? | TODO: single characters, common usage in function names |
| How do you define a function in Haskell? | TODO
For example: add x y = x + y
|
| Didn't you say Haskell is statically typed? | It is. TODO |
| What is the meaning of the double dash "--"? | "-- " (a trailing space is necessary) begins a single-line comment. The rest of the line will be ignored by the compiler.
For example: -- Sort the list
sort [3,2,4]
or sort [3,2,4] -- Sort the list
|
| What is the meaning of "{-" and "-}"? | "{- " (a trailing space is necessary) and "-}" define a block comment. Everything in between will be ignored by the compiler.
For example: {-
The next line would sort the list, if it wasn't in a block comment
sort [3,2,4]
-}
|
| What is the meaning of the dollar sign "$"? | "$" is a way to compose functions, but avoid typing too many brackets.
For example: foo x = h (g (f x))
is the same as foo x = h $ g $ f x
|
| What is the meaning of the dot "."? | "." is used to compose functions in point-free style, similar to "$".
For example: foo x = h $ g $ f x
is the same as foo = h . g . f
|
| What is point-free style? | Point-free style is a way to define functions solely as a composition of other functions, leaving out arguments in the definition.
For example: takeFive x = take 5 x
is the same as takeFive = take 5
in point-free style. |
| What is the meaning of "data"? | "data" defines a new data type. TODO
For example: data colors = Red | Blue | Green
|
| What is currying? | TODO |
| What is pattern matching? | TODO |
Advanced
| Question | Answer |
|---|---|
| What is the meaning of "{-#" and "#-}"? | "{-# " (the trailing space is necessay) and "#-}" define compiler pragmas. TODO |
| What is a Monad? | TODO |
| What is the meaning of "forall"? | TODO |
Special characters and keywords
\
Backslash TODO: multiline strings, lambda function
|
Downslash TODO: pattern matching, data types
deriving
TODO
newtype
TODO
type
TODO