Code Smell 89 - Math Feature Envy

Code Smell 89 - Math Feature Envy

Maxi Contieri
·Oct 4, 2021·

2 min read

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One class calculating formulas for another class.

TL;DR: Leave the formulas to the objects gathering the information.


  • Declaratively

  • Low reuse

  • Real-world concept missing

  • Encapsulation


  1. Move the math formula to the class

  2. Search for real-world abstractions

Sample Code


function area(rectangle) { 
  return rectange.width * rectangle.height;
  //Notice we are sending consecutive messages to
  //the same object and doing calculations
class Rectangle {
    constructor(width, height, color) { 
         this.height = height;
         this.width = width;

    area() {
        return this.width * this.height;


Since many cascading messages are sending to the same object, we can detect a pattern.


  • Encapsulation

  • Coupling


This is a very basic smell. If we are manipulating another object characteristics, we should let it do it the maths for us.


More Info


Photo by Michal Matlon on Unsplash

Computer science is not about machines, in the same way that astronomy is not about telescopes. There is an essential unity of mathematics and computer science.

Michael R. Fellows

This article is part of the CodeSmell Series.

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