[Learning you a Haskell for great goods!] Chapter 01 starting out

Installation

Under centos/Fedora

# Yum install ghc

 

Version

[[Email protected] Haskell] # ghc-V

Glasgow Haskell compiler, version 7.0.4, for Haskell 98, Stage 2 booted by ghc version 7.0.4

 

Change Prompt

Echo: set prompt "ghci>"> ~ /. Ghci

 

Command

# Boolean

Ghci> true & false

False

 

# Call function, get successor of 8

Ghci> succ 8

9

 

# Load scripts

# Echo doubleme x = x + x> baby. Hs

 

Ghci>: l baby. Hs

[1 of 1] compiling main (baby. Hs, interpreted)

OK, modules loaded: Main.

 

Ghci> doubleme 9

18

 

# Concatenation between list and string

Ghci> [1, 2, 4] ++ [9, 10, 11, 12]

[1, 2, 3, 4, 9, 10, 11, 12]

 

Or

 

Ghci> 'A': "Small Cat"

"A small cat"

 

Or

 

Ghci> 5: [1, 2]

[5, 1, 2]

 

# List Operation

 

# Get the element that's Index = 3

Ghci> "123456 "!! 3

'4'

 

# Comparing

Ghci> [3, 2, 1]> [2, 1, 0]
True

# Head vs tail, init vs last

Ghci> head [5, 4, 3, 2, 1]
5

Ghci> tail [5, 4, 3, 2, 1]
[4, 3, 2, 1]

Ghci> last [5, 4, 3, 2, 1]
1

Ghci> init [5, 4, 3, 2, 1]
[5, 4, 3, 2]

# Length

Ghci> length [5, 4, 3, 2, 1]
5

# Is null or not

Ghci> null [1, 2, 3]
False
Ghci> null []
True

# Reverse list

Ghci> reverse [5, 4, 3, 2, 1]
[1, 2, 3, 4, 5]

# Take the first n elements

Ghci> take 3 [5, 4, 3, 2, 1]
[5, 4, 3]
Ghci> take 1 [3, 9, 3]
[3]
Ghci> take 5 [1, 2]
[1, 2]
Ghci> take 0 [6, 6]
[]

# Drop the first n elements

Ghci> drop 3 [,]
[1, 5, 6]
Ghci> drop 0 [1, 2, 4]
[1, 2, 3, 4]
Ghci> drop 100 [,]
[]

# Element in list or not

Ghci> 4 'elem '[1, 4]
True

Or

Ghci> ELEM 4 [1, 4]
True

# Range

Ghci> [1 .. 4]
[1, 2, 3, 4]

 

# Replicate

Ghci> replicate 3 10
[10, 10, 10]

# List Comprehension

Ghci> [x * 2 | x <-[1 .. 10]
[,]

Ghci> [x * 2 | x <-[1 .. 10], x * 2> = 12]

[, 20]

 

 

 

 

 

 

Note

Doublesmallnumber 'is valid as a method name

[Learning you a Haskell for great goods!] Chapter 01 starting out