Condition Yoda, good reason to use?

Question

Question mainly in PHP, in the Wordpress documentation exists an excerpt which explicitly speaks that it is interesting to use the famous Yoda conditions, although it does not give a good and real reason.

When making logical comparisons involving variables, always put the variable on the right side and put constants, literals or calls function on left side. (Free Translation)

Specifically me, always found ugly and read not easy this kind of coding: if(10 == $teste){ // do anything } or if("string" == $teste){ // do anything }

This doubt arose me after a colleague of mine recommend me to install a plugin in Brackets called Brackets php code quality tools that theoretically points out errors in coding... and in lines of the type if($teste == 10){ // do anything } he generates warnings, he recommends the use of the blessed Yoda conditions.

The first time I saw this type of coding came into my mind to be to facilitate the processing, like first the processor just picks up the constant and then accesses the location of the variable in memory, but stopping to think I see no difference!

I did tests in PHP and Javascript and saw no difference in performance with the naked eye...

Follows tests:

PHP

echo "Normal<br/>";
$a = "a";
for($x = 0; $x <= 5; $x++){
    $time_start = microtime(true);
    if($a == "a"){
        //
    }
    $execution_time = microtime(true) - $time_start;
    echo $execution_time.'s<br/>';
}
echo "-------------<br/>";
echo "Yoda Condition<br/>";
$a = "a";
for($x = 0; $x <= 5; $x++){
    $time_start = microtime(true); 
    if("a" == $a){
        //
    }
    $execution_time = microtime(true) - $time_start;
    echo $execution_time.'s<br/>';
}

Javascript

Is there a good reason to use Yoda Conditions in some programming language? Or is it just the customer’s taste? Is there any difference in performance (in some language)?

Answer 1

The only advantage of Yoda conditions is change the error type, logic (assignment instead of comparison) by a syntax. It is not possible to assign something directly to a number or any other type.

Basically Yoda conditions make the code fail faster in case of errors while performace is still the same comparison; so it does not affect anything.

Is it worth sacrificing readability to detect this kind of mistake sooner? It is a simple mistake that can sometimes cause a little headache, in these situations it is best to take a break and cool your head.

<?php
$usuario = 'teste';
if('admin' = $nome){
    echo 'administrador do sistema';
}

PHP Parse error: syntax error, Unexpected '='

Example - ideone

Answer 2

Java uses something similar for comparisons involving a literal string (between quotes) or another already instantiated object:

if ("Mario".equals(nome)) {

The utility is to save a null reference test. If the programmer doesn’t want to do this check or forget to do it, but is used to reversing the condition, you can avoid a NullPointerException that could occur if called equals() from a null reference.

Answer 3

The advantage of Yoda conditions is to expose possible bugs by typos, replacing a == for =.

In the code below, the condition will always return true, causing unexpected application behavior - which could take some time to discover.

<?php
$usuario = 'teste';
if($usuario = 'admin'){
    echo 'administrador do sistema';
}
?>

Using Yoda condition, you would receive a syntax error while running this code, noticing and fixing the problem immediately.

<?php
$usuario = 'teste';
if('admin' = $usuario){
    echo 'administrador do sistema';
}
?>

So you get a performance gain not in code execution, but in preventing bugs.