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Haskell Program To Check Whether The Input Number Is A Palindrome
This tutorial discusses writing a program to check whether the input number is a Palindrome number in the Haskell programming language.
A number can be called as a palindrome when it results in the same number when the digits are reversed. For Example, the number 12321 is a palindrome, because after reversing the digits it results in the same number.
In this tutorial we see,
Program to check whether the input number is a palindrome using the string reverse function.
Program to check whether the input number is a palindrome using the recursive function.
Method 1: Checking Palindrome using String Reverse Function
Algorithm Steps
We declared a function isPalindrome which takes an integer as an argument and returns a boolean value.
Using the "Where" keyword to express the logic in multiple statements
Converting the number to number to string using the function show and
Reversing the string by using the function reverse
Comparing both the strings
Printing the results as per the boolean expression got from comparison
Example
-- function declaration
isPalindrome :: Int->Bool
-- function definition
isPalindrome n = (n == k)
where
-- Converting integer to string using function show
nStr = reverse (show n)
-- Converting string to an integer using function read
k = (read nStr :: Int)
main :: IO()
main = do
-- initializing variable num
let num = 12321
-- invoking the function isPalindrome
let status = isPalindrome num
-- printing the status
if(status==True)
then print ("The number " ++ show num ++ " is a palindrome")
else print ("The number " ++ show num ++ " is not a palindrome")
Output
"The number 12321 is a palindrome"
Method 2: Checking Palindrome using String Recursive Function
Algorithm
We declared a function isPalindrome as such it takes three integer arguments and returns a boolean value.
Create a main function and define a value to check whether it is a palindrome or not.
Initiailize the Palendrom function in the main function towards the defined number.
Print the result as per the boolean expression got from the Palendrom function.
Example
Program to check whether the input number is a palindrome using the recursive function
-- function declaration
isPalindrome :: Int->Int->Int->Bool
-- function definition
isPalindrome num a revNum = if(a==0)
then if (revNum == num)
then True
else False
else k
where
d = mod a 10
newRevNum = revNum*10 + d
newA = div a 10
k = isPalindrome num newA newRevNum
main :: IO()
main = do
-- initializing variable num
let num = 1256521
-- invoking the function isPalindrome
let status = isPalindrome num num 0
-- printing the status
if(status==True)
then print ("The number " ++ show num ++ " is a palindrome")
else print ("The number " ++ show num ++ " is not a palindrome")
Output
"The number 1256521 is a palindrome"
Conclusion
In this tutorial, we discussed two ways to implement a program to check whether the number is a palindrome in the Haskell programming Language.
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