#6 Xbase Number Literals

Jul 08, 2012 | 6 minutes | Beginners, Xtend

This episode shows, how to significantly simplify java BigDecimal expressions using the Xbase operator overloading together with the "bd" number literal.

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What's new in Xtext 2.3: http://www.eclipse.org/Xtext/releasenotes/2.3.0/new_and_noteworthy.php

Xbase expression operators (for operator overloading):
http://www.eclipse.org/Xtext/documentation.html#Xbase_Expressions_Operators

Tax rates example: http://en.wikipedia.org/wiki/Tax#Tax_rates

              xtend
                    
        package test

import java.math.BigDecimal
import static extension test.MyMath.*

class TaxRates2 {
  /**
   * Income is taxed on a formula of 5% from $0 up to $50,000,
   * 10% from $50,000 to $100,000, and 15% over $100,000.
   * 
   * @param income income to pay taxes from
   * @return effective tax rate
   */
  def static BigDecimal effectiveRate(BigDecimal income) {
    var tax = 0.05bd * income
    if (income > 50_000bd) {
      tax = tax + 0.05bd * (income - 50_000bd)
    }
    if (income > 100_000bd) {
      tax = tax + 0.05bd * (income - 100_000bd)
    }
    tax / income * 100bd
  }

}
        
        
        
        
        
        
        
        
        
      
package test

import java.math.BigDecimal
import static extension test.MyMath.*

class TaxRates2 {
  /**
   * Income is taxed on a formula of 5% from $0 up to $50,000,
   * 10% from $50,000 to $100,000, and 15% over $100,000.
   * 
   * @param income income to pay taxes from
   * @return effective tax rate
   */
  def static BigDecimal effectiveRate(BigDecimal income) {
    var tax = 0.05bd * income
    if (income > 50_000bd) {
      tax = tax + 0.05bd * (income - 50_000bd)
    }
    if (income > 100_000bd) {
      tax = tax + 0.05bd * (income - 100_000bd)
    }
    tax / income * 100bd
  }

}

              MyMath.xtend
                    
        package test

import java.math.BigDecimal
import java.math.MathContext

class MyMath {
  def static operator_divide(BigDecimal a, BigDecimal b) {
    a.divide(b, MathContext::DECIMAL64)
  }
  
  def static operator_multiply(BigDecimal a, BigDecimal b) {
    a.multiply(b, MathContext::DECIMAL64)
  }
}
        
package test

import java.math.BigDecimal
import java.math.MathContext

class MyMath {
  def static operator_divide(BigDecimal a, BigDecimal b) {
    a.divide(b, MathContext::DECIMAL64)
  }
  
  def static operator_multiply(BigDecimal a, BigDecimal b) {
    a.multiply(b, MathContext::DECIMAL64)
  }
}