3. HC3 ‐ Haskell Chapter 3 Practical Tasks: Conditions‐and‐helper‐constructions

HC3T1 - Task 1: Check if a number is positive, negative, or zero

1. Define a function checkNumber :: Int -> String.
2. Use an if-then-else statement to check if the number is positive, negative, or zero.
3. Return "Positive", "Negative", or "Zero" accordingly.
4. Test your function with checkNumber 5, checkNumber (-3), and checkNumber 0.

HC3T2 - Task 2: Determine the grade based on a score using guards

1. Define a function grade :: Int -> String.
2. Use guards (|) to classify scores into grades:
   • 90 and above: "A"
   • 80 to 89: "B"
   • 70 to 79: "C"
   • 60 to 69: "D"
   • Below 60: "F"
3. Test your function with grade 95, grade 72, and grade 50.

HC3T3 - Task 3: Convert an RGB color to a hex string using let bindings

1. Define a function rgbToHex :: (Int, Int, Int) -> String.
2. Use let bindings to format each color component as a two-character hex string.
3. Concatenate the three hex values into a single string.
4. Test your function with rgbToHex (255, 0, 127) and rgbToHex (0, 255, 64).

HC3T4 - Task 4: Calculate the area of a triangle using Heron's formula

1. Define a function triangleArea :: Float -> Float -> Float -> Float.
2. Use let to calculate the semi-perimeter s.
3. Apply Heron’s formula: sqrt(s * (s - a) * (s - b) * (s - c)).
4. Test with triangleArea 3 4 5 and triangleArea 7 8 9.

HC3T5 - Task 5: Determine the type of a triangle using guards

1. Define a function triangleType :: Float -> Float -> Float -> String.
2. Use guards to classify the triangle:
   • All sides equal: "Equilateral"
   • Two sides equal: "Isosceles"
   • No sides equal: "Scalene"
3. Test with triangleType 3 3 3, triangleType 5 5 8, and triangleType 6 7 8.

HC3T6 - Advanced Task 6: Check leap year using if-then-else

1. Define isLeapYear :: Int -> Bool.
2. Use if-then-else to check:
   • Divisible by 400: True
   • Divisible by 100 but not 400: False
   • Divisible by 4: True
   • Otherwise: False
3. Test with isLeapYear 2000, isLeapYear 1900, and isLeapYear 2024.

HC3T7 - Advanced Task 7: Determine the season based on the month using guards

1. Define season :: Int -> String.
2. Use guards to return:
   • 12, 1, 2 -> "Winter"
   • 3, 4, 5 -> "Spring"
   • 6, 7, 8 -> "Summer"
   • 9, 10, 11 -> "Autumn"
3. Test with season 3, season 7, and season 11.

HC3T8 - Advanced Task 8: Calculate BMI and return category using where

1. Define bmiCategory :: Float -> Float -> String.
2. Use where to calculate BMI: bmi = weight / height^2.
3. Use guards to classify BMI:
   • <18.5: "Underweight"
   • 18.5 to 24.9: "Normal"
   • 25 to 29.9: "Overweight"

   • =30: "Obese"

4. Test with bmiCategory 70 1.75 and bmiCategory 90 1.8.

HC3T9 - Advanced Task 9: Find the maximum of three numbers using let

1. Define maxOfThree :: Int -> Int -> Int -> Int.
2. Use let to store intermediate max values.
3. Return the maximum of the three numbers.
4. Test with maxOfThree 10 20 15 and maxOfThree 5 25 10.

HC3T10 - Advanced Task 10: Check if a string is a palindrome using recursion and guards

1. Define isPalindrome :: String -> Bool.
2. Use guards:
   • If the string has 0 or 1 characters: True
   • If the first and last characters match, recursively check the rest.
   • Otherwise, return False.
3. Test with isPalindrome "racecar", isPalindrome "haskell", and isPalindrome "madam".

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