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complex number assignment

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Sebastian Steger 2025-08-20 15:29:24 +02:00
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# Complex Numbers
## Assignment
Define a new type `Complex` that allows arithmetic calculations in an intuitive fashion. See below for the rules that shall be implemented. Incrementally make sure that all unit tests in `06-complex/complex.hs` are passed.
## Complex Numbers
Complex numbers are numbers of the form: $z = a + bi$
- **`a`**: The real part of the complex number.
- **`b`**: The imaginary part of the complex number.
- **`i`**: The imaginary unit, where $i^2 = -1$.
Complex numbers are used in mathematics, physics, and engineering to extend the real number system and solve equations that have no real solutions, such as $x^2 + 1 = 0$.
Complex numbers are often represented in both rectangular form $a + bi$ and polar/exponential form $r e^{i\theta}$.
## Rules for Computing with Complex Numbers
### 1. **Addition and Subtraction**
- Add or subtract the real and imaginary parts separately.
- Rule:
$(a + bi) + (c + di) = (a + c) + (b + d)i$
$(a + bi) - (c + di) = (a - c) + (b - d)i$
**Examples**:
1. $(2 + 3i) + (4 + 5i) = 6 + 8i$
2. $(0 + 3i) + (2 + 0i) = 2 + 3i$
3. $(7 + 2i) - (3 + 6i) = 4 - 4i$
4. $(5 + 4i) - (1 + 2i) = 4 + 2i$
### 2. **Multiplication**
- Use the distributive property and the rule $i^2 = -1$.
- Rule:
$(a + bi)(c + di) = (ac - bd) + (ad + bc)i$
**Examples**:
1. $(1 + 2i)(3 + 4i) = -5 + 10i$
2. $(2 + 3i)(1 - i) = 5 + i$
3. $(4 + i)(2 - 3i) = 11 - 10i$
4. $(3 + 2i)(3 + 2i) = 5 + 12i$
### 3. **Division**
- Multiply numerator and denominator by the conjugate of the denominator.
- Rule:
$\frac{a + bi}{c + di} = \frac{(a + bi)(c - di)}{(c + di)(c - di)}$
Simplifies to:
$\frac{(ac + bd) + (bc - ad)i}{c^2 + d^2}$
**Examples**:
1. $\frac{1 + i}{1 - i} = 0 + 1i$
2. $\frac{3 + 2i}{4 + 3i} = \frac{18 + i}{25} = 0.72 - 0.04i$
3. $\frac{2 + i}{1 + i} = \frac{3 - i}{2} = 1.5 - 0.5i$
### 4. **Complex Conjugate**
- The conjugate of $a + bi$ is $a - bi$, used for simplifications and magnitude calculation.
**Examples**:
1. Conjugate of $3 + 4i$ is $3 - 4i$.
2. Conjugate of $5 - i$ is $5 + i$.
3. Conjugate of $-2 + 3i$ is $-2 - 3i$.
### 5. **Magnitude (Modulus)**
- The magnitude is the distance from the origin in the complex plane.
- Rule: $|a + bi| = \sqrt{a^2 + b^2}$
**Examples**:
1. $|3 + 4i| = \sqrt{3^2 + 4^2} = 5$
2. $|1 - i| = \sqrt{1^2 + (-1)^2} = \sqrt{2}$
3. $|0 + 5i| = \sqrt{0^2 + 5^2} = 5$

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{-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
{-# HLINT ignore "Use void" #-}
import Test.HUnit
data Complex a = TODO
instance (Show a, Num a, Eq a) => Show (Complex a) where
-- show :: (Show a, Num a, Eq a) => Complex a -> String
-- TODO
instance (Num a, Floating a) => Num (Complex a) where
-- (+) :: (Num a, Floating a) => Complex a -> Complex a -> Complex a
-- (*) :: (Num a, Floating a) => Complex a -> Complex a -> Complex a
-- TODO
-- abs (Complex re im) = TODO
-- signum (Complex re im) = TODO
-- fromInteger n = TODO
-- negate :: (Num a, Floating a) => Complex a -> Complex a
-- negate (Complex re im) = Complex (negate re) (negate im)
instance (Fractional a, Floating a) => Fractional (Complex a) where
-- fromRational r = TODO
-- recip (Complex re im) = TODO
-- (Complex re1 im1) / (Complex re2 im2) = TODO
-- conj :: Num a => Complex a -> Complex a
-- TODO
tests :: Test
tests =
TestList
[
-- Test.HUnit.TestCase (assertEqual "Show 1+2i" "1+2i" (show $ Complex 1 2)),
-- Test.HUnit.TestCase (assertEqual "Show 1" "1" (show $ Complex 1 0)),
-- Test.HUnit.TestCase (assertEqual "Show i" "i" (show i)),
-- Test.HUnit.TestCase (assertEqual "Show 5i" "5i" (show $ Complex 0 5)),
-- Test.HUnit.TestCase (assertEqual "Show 0" "0" (show $ Complex 0 0)),
-- Test.HUnit.TestCase (assertEqual "Compare Equal" True (Complex 2 3 == Complex 2 3)),
-- Test.HUnit.TestCase (assertEqual "Compare Real Not Equal" False (Complex 1 3 == Complex 2 3)),
-- Test.HUnit.TestCase
-- (assertEqual "Compare Imag Not Equal" False (Complex 2 4 == Complex 2 3)),
-- Test.HUnit.TestCase
-- (assertEqual "Compare Not Equal" False (Complex 2 3 /= Complex 2 3)),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Addition 1"
-- (Complex 6.0 8.0)
-- (Complex 2.0 3.0 + Complex 4.0 5.0)
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Addition 2"
-- (Complex 2.0 3.0)
-- (Complex 0.0 3.0 + Complex 2.0 0.0)
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Subtraction 1"
-- (Complex 4.0 (-4.0))
-- (Complex 7.0 2.0 - Complex 3.0 6.0)
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Subtraction 2"
-- (Complex 4.0 2.0)
-- (Complex 5.0 4.0 - Complex 1.0 2.0)
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Negation"
-- (Complex (-7.0) (-2.0))
-- (negate (Complex 7.0 2.0))
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Multiplication 1"
-- (Complex (-5.0) 10.0)
-- (Complex 1.0 2.0 * Complex 3.0 4.0)
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Multiplication 2"
-- (Complex 5.0 1.0)
-- (Complex 2.0 3.0 * Complex 1.0 (-1.0))
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Multiplication 3"
-- (Complex 11.0 (-10.0))
-- (Complex 4.0 1.0 * Complex 2.0 (-3.0))
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Multiplication 4"
-- (Complex 5.0 12.0)
-- (Complex 3.0 2.0 * Complex 3.0 2.0)
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Magnitude 1"
-- (Complex 5.0 0.0)
-- (abs (Complex 3.0 4.0))
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Magnitude 2"
-- (Complex (sqrt 2.0) 0.0)
-- (abs (Complex 1.0 (-1.0)))
-- ),
-- Test.HUnit.TestCase
-- ( assertEqual
-- "Magnitude 3"
-- (Complex 5.0 0.0)
-- (abs (Complex 0.0 5.0))
-- ),
-- TestCase (assertEqual "Conjugate of 3+4i" (Complex 3 (-4)) (conj (Complex 3 4))),
-- TestCase (assertEqual "Conjugate of 5-i" (Complex 5 1) (conj (Complex 5 (-1)))),
-- TestCase (assertEqual "Conjugate of -2+3i" (Complex (-2) (-3)) (conj (Complex (-2) 3)))
]
main :: IO ()
main = runTestTT tests >> return ()