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haskell.md

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128 lines (103 loc) · 3.2 KB
title Haskell
description Quick reference to Haskell cheat sheet which will increase your productivity as it contains useful syntax and is very handy while coding.
created 2020-06-25
updated 2020-06-25

Sample program

main = do  
    name <- getLine  
    putStrLn ("Hello " ++ name ++ ", Happy learning!")

  • main : entry point of the program

  • getLine : reads input data from Console

  • putStrLn : prints data to the console.

  • -- : Single line comment

  • {- Multi

    Line

    comment -}

Data types

Data-type Description
Numbers Haskell is intelligent to identify numbers without specifying data type
Characters Haskell is intelligent to identify characters and strings without specifying data type
Tuple To declare multiple values in a single data type. Tuples are represented in single paranthesis. For example (10,20,'apple')
Boolean To represent boolean values, true or false
List To declare same type of values in a single data type. Lists are represented in square braces.For example [1,2,3] or `['a','b','c','d']

Reserved keywords

|||| |----|----|----|----| | case | class | data| deriving| | do | else | if |import| | in | infix | infixl | infixr| | instance | let | of | module| | newtype | then | type | where

Operators

Type Operators
Arithmetic Operators + , - , * , / , % , **, &&, ||, not
Comparision Operators == , /= , > , >= , < , <=
Bitwise Operators & , ^ , | , ^ , ~ , << , >> , >>>
Function Operators , ., |
List Operators [...,...], ++, :, !!, .. , \, <-
Monad Operators :, ->, ::, =>, (), >>, >>=, >@>,(..)
Pattern Operators _, ~, !, @

Conditional Statements

If-Else

if conditional-expression
  then true statements 
  else false statements

Case

 case exp of
     Pattern1  -> action1
     Pattern2  -> action2
     _         -> else_action

Tuples

Tuples are used to group data of different types(similar type is also allowed)

(item1,item2,[itemn…])

Example

(1, "John", 35.2, true)

Lists

Lists are usually used to group data of similar types

[item1, item2,[itemn]]

Example

[1,2,3,4,5,6,7,8,9,10]
[1..10]

Both the above gives the same meaning as you can also use range to define lists

Some of the common list operations

List Operations Description
list1+list2 to append two lists list1+list2
list1!!n to return element n from list1
head/last list1 to retrieve the first/last element of the list1
sum list1 to get the sum of all list elements present in list1
prod list1 to get the product of all list elements present in list1
reverse list1 to reverse the elements present in list1

Functions

How to define and call a Function

functionname :: data type [-> datatype] -> data type -- function definition 
--code

functionname(variable) -- calling a function

Examples

multiply :: Integer -> Integer -> Integer   --declaration of a function 
multiply x1 x2 =  x1 * x2                       --definition of a function

main = do 
   putStrLn "Multiplication value is:"  
   print(multiply 10 5)    --calling a function