03: Java FP composing functions example – calculate discount

Posted on August 18, 2017 by

FP – calculate the invoice price Invoice Price = (markedPrice * (100 – discountRate)/100) + deliveryCharge Example

package com.fp.eg3;
import java.util.function.Function;
public class DiscountCalcFPMain {
    
    public static void main(String[] args) {
        
        double markedPrice = 300.00;
        double discountRate = 10.00 ; //10%
        double deliveryCharge = 50.00;
        
        DiscountCalaculator dc = new DiscountCalaculator();
    
        Function<Double, Double> f = dc.currySecondArg((100 - discountRate)/100);
        Function<Double, Double> g = x -> x + deliveryCharge;
        
        Function<Double, Double> h = f.andThen(g);
        System.out.println("Invoice Price = " + h.apply(markedPrice)); // 320.00
    }
}

package com.fp.eg3;

import java.util.function.Function;

public class DiscountCalcFPMain {

public static void main(String[] args) {

double markedPrice = 300.00;

double discountRate = 10.00 ; //10%

double deliveryCharge = 50.00;

DiscountCalaculator dc = new DiscountCalaculator();

Function<Double, Double> f = dc.currySecondArg((100 - discountRate)/100);

Function<Double, Double> g = x -> x + deliveryCharge;

Function<Double, Double> h = f.andThen(g);

System.out.println("Invoice Price = " + h.apply(markedPrice)); // 320.00

}

“f.andThen(g)” is the composition of functions. This can be described as g(f()) where f() is 270.0 (i.e. 300.00 * (100 – 10)/100),…

03: Java FP composing functions example – calculate discount

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