feat: Finish part - 4

bin/main.dart

@@ -1,6 +1,7 @@
 import 'package:dart_basics/basic_part1.dart' as part1;
 import 'package:dart_basics/basic_part2.dart' as part2;
 import 'package:dart_basics/basic_part3.dart' as part3;
+import 'package:dart_basics/basic_part4.dart' as part4;
 
 main(List<String> arguments) {
   // Part 1
@@ -14,4 +15,7 @@ main(List<String> arguments) {
   // Part 3
   part3.basic_operators();
   part3.basic_classes();
+
+  // Part 4
+  part4.basic_classes();
 }

lib/basic_part3.dart

@@ -142,6 +142,3 @@ class Complex {
     }
   }
 }
-
-
-

lib/basic_part4.dart

@@ -0,0 +1,69 @@
+void basic_classes() {
+  var n1 = Complex(3, -4);
+  var n2 = Complex(5, 2);
+
+  print(n1 + n2);
+  print(n1.multiply(n2));
+  print(Complex.substract(n1, n2));
+}
+
+class Complex {
+  // Private property(member)
+  num _real;
+  num _imaginary;
+
+  // Getters & Setters
+  get real => _real;
+  set real(num newReal) => _real = newReal;
+
+  get imaginary => _imaginary;
+  set imaginary(num newImaginary) => _imaginary = newImaginary;
+
+  // Constructors
+  Complex(this._real, this._imaginary);
+  Complex.real(num real) : this(real, 0);
+  Complex.imaginary(num imaginary) : this(0, imaginary);
+
+  Complex operator +(Complex c) {
+    return Complex(this.real + c.real, this.imaginary + c.imaginary);
+  }
+
+  Complex operator *(Complex c) {
+    return Complex(
+      (this.real * c.real) - (this.imaginary * c.imaginary),
+      (this.real * c.imaginary) + (this.imaginary * c.real),
+    );
+  }
+
+  Complex multiply(Complex c) {
+    return Complex(
+      (this.real * c.real) - (this.imaginary * c.imaginary),
+      (this.real * c.imaginary) + (this.imaginary * c.real),
+    );
+  }
+
+  static Complex substract(Complex c1, Complex c2) {
+    return Complex(
+      c1.real - c2.real,
+      c1.imaginary - c2.imaginary,
+    );
+  }
+
+  @override
+  bool operator ==(dynamic other) {
+    if (other is! Complex) {
+      return false;
+    } else {
+      return real == other.real && imaginary == other.imaginary;
+    }
+  }
+
+  @override
+  String toString() {
+    if (imaginary >= 0) {
+      return "$real + ${imaginary}i";
+    } else {
+      return "$real - ${imaginary.abs()}i";
+    }
+  }
+}