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Task/Numeric-error-propagation/Java/numeric-error-propagation.java

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+public class Approx {
+    private double value;
+    private double error;
+
+    public Approx(){this.value = this.error = 0;}
+
+    public Approx(Approx b){
+        this.value = b.value;
+        this.error = b.error;
+    }
+
+    public Approx(double value, double error){
+        this.value = value;
+        this.error = error;
+    }
+
+    public Approx add(Approx b){
+        value+= b.value;
+        error = Math.sqrt(error * error + b.error * b.error);
+        return this;
+    }
+
+    public Approx add(double b){
+        value+= b;
+        return this;
+    }
+
+    public Approx sub(Approx b){
+        value-= b.value;
+        error = Math.sqrt(error * error + b.error * b.error);
+        return this;
+    }
+
+    public Approx sub(double b){
+        value-= b;
+        return this;
+    }
+
+    public Approx mult(Approx b){
+        double oldVal = value;
+        value*= b.value;
+        error = Math.sqrt(value * value * (error*error) / (oldVal*oldVal) +
+                                  (b.error*b.error) / (b.value*b.value));
+        return this;
+    }
+
+    public Approx mult(double b){
+        value*= b;
+        error = Math.abs(b * error);
+        return this;
+    }
+
+    public Approx div(Approx b){
+        double oldVal = value;
+        value/= b.value;
+        error = Math.sqrt(value * value * (error*error) / (oldVal*oldVal) +
+                                  (b.error*b.error) / (b.value*b.value));
+        return this;
+    }
+
+    public Approx div(double b){
+        value/= b;
+        error = Math.abs(b * error);
+        return this;
+    }
+
+    public Approx pow(double b){
+        double oldVal = value;
+        value = Math.pow(value, b);
+        error = Math.abs(value * b * (error / oldVal));
+        return this;
+    }
+
+    @Override
+    public String toString(){return value+"±"+error;}
+
+    public static void main(String[] args){
+        Approx x1 = new Approx(100, 1.1);
+        Approx x2 = new Approx(50, 1.2);
+        Approx y1 = new Approx(200, 2.2);
+        Approx y2 = new Approx(100, 2.3);
+
+        x1.sub(x2).pow(2).add(y1.sub(y2).pow(2)).pow(0.5);
+
+        System.out.println(x1);
+    }
+}