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Haskell Program to Print Diamond Star Pattern
In Haskell, to print Diamond star pattern we will be using mapM_, reverse, unlines and replicate functions. In the first example, we are going to use ( diamondStarPattern n = unlines $ topHalf ++ bottomHalf where topHalf = [replicate (n - i) ' ' ++ replicate ((2 * i) - 1) '*' | i <- [0..n]] and bottomHalf = reverse $ drop 0 topHalf) function and in the second example, we are going to use, (diamondStarPattern n = mapM_ putStrLn $ bottomRows ++ topRows where topRows = [spaces i ++ stars (n - 2 * i) | i <- [0..n `div` 2]] and bottomRows = reverse [spaces i ++ stars (n - 2 * i) | i <- [1..n `div` 2]]) function.
Algorithm
Step 1 − The diamondStarPattern function is defined using mapM_ and reverse functions
Step 2 − The program execution will be started from main function. The main() function has whole control of the program.
Step 3 − The resultant diamond star pattern is printed to the console, once the function is being called with argument.
Example 1
In this example, the diamond star pattern is printed using unlines and replicate function.
main = do
let n = 3
putStrLn $ diamondStarPattern n
diamondStarPattern :: Int -> String
diamondStarPattern n = unlines $ topHalf ++ bottomHalf
where topHalf = [replicate (n - i) ' ' ++ replicate ((2 * i) - 1) '*' | i <- [0..n]]
bottomHalf = reverse $ drop 0 topHalf
Output
[1 of 1] Compiling Main ( main.hs, main.o ) Linking main ... * *** ***** ***** *** *
Example 2
In this example, the diamond star pattern is printed using mapM_ and reverse function.
diamondStarPattern :: Int -> IO ()
diamondStarPattern n = mapM_ putStrLn $ bottomRows ++ topRows
where
topRows = [spaces i ++ stars (n - 2 * i) | i <- [0..n `div` 2]]
bottomRows = reverse [spaces i ++ stars (n - 2 * i) | i <- [1..n `div` 2]]
stars x = replicate x '*'
spaces x = replicate x ' '
main = diamondStarPattern 7
Output
[1 of 1] Compiling Main ( main.hs, main.o ) Linking main ... * *** ***** ******* ***** *** *
Conclusion
The diamond star pattern is a pattern made up of asterisks (*) arranged in the shape of a diamond. The pattern consists of two parts - an upper triangle and a lower triangle. The upper triangle is formed by a series of lines that gradually decrease in length from the center until they meet at a point at the top. The lower triangle is formed by a series of lines that gradually increase in length from the center until they reach the maximum width at the bottom. The two triangles are separated by a single line of asterisks. The overall effect is a diamond shape with a star pattern.
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