PHP: Ternary operator
Look at the definition of this function, which returns the modulus of a given number:
<?php
function abs($number)
{
if ($number >= 0) {
return $number;
}
return -$number;
}
abs(10); // 10
abs(-10); // 10
Can we write it more concisely? Something like return return ОТВЕТ В ЗАВИСИМОСТИ ОТ УСЛОВИЯ? That would require an expression following return, but if is a statement, not an expression.
In PHP, there's a construct that works like the*if-else* construct, but is an expression. It's called the ternary operator.
The ternary operator is the only JavaScript operator that takes three operands:
<?php
function abs($number)
{
return $number >= 0 ? $number : -$number;
}
It generally looks like this: <predicate> ? <expression on true> : <expression on false>.
Let's rewrite the initial version of getTypeOfSentence() in the same way:
Before:
<?php
function getTypeOfSentence($sentence)
{
$lastChar = substr($sentence, -1);
if ($lastChar === '?') {
return 'question';
}
return 'normal';
}
After:
<?php
function getTypeOfSentence($sentence)
{
$lastChar = substr($sentence, -1);
return ($lastChar === '?') ? 'question' : 'normal';
}
getTypeOfSentence('Hodor'); // normal
getTypeOfSentence('Hodor?'); // question
If you remember the main strength of expressions, then you probably figured out by now that you can nest a ternary operator in another ternary operator. ** Don't do it :)** This sort of code is hard both to read and to debug, it's very bad practice.
Instructions
Implement the flipFlop() function, which takes a string as input and, if that string is 'flip', it returns the string 'flop'. Otherwise, the function needs to return 'flip'.
Call examples:
<?php
flipFlop('flip'); // 'flop'
flipFlop('flop'); // 'flip'
Try writing two versions of the function: one with the usual if-else, and one with a ternary operator.
The exercise doesn't pass checking. What to do? 😶
If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:
- Be sure to attach the test output, without it it's almost impossible to figure out what went wrong, even if you show your code. It's complicated for developers to execute code in their heads, but having a mistake before their eyes most probably will be helpful.
In my environment the code works, but not here 🤨
Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.
My code is different from the teacher's one 🤔
It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.
In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.
I've read the lessons but nothing is clear 🙄
It's hard to make educational materials that will suit everyone. We do our best but there is always something to improve. If you see a material that is not clear to you, describe the problem in “Discussions”. It will be great if you'll write unclear points in the question form. Usually, we need a few days for corrections.
By the way, you can participate in courses improvement. There is a link below to the lessons course code which you can edit right in your browser.
Definitions
The ternary operator is a way to turn a simple conditional instruction into an expression, e.g.,
$number >= 0 ? $number : -$number.