2nd hardest thing in computer science

2nd hardest thing in computer science

Definition?

“There are only two hard things in Computer Science: cache invalidation and naming things.” Phil Carton

#2 Naming things*

*things variables methods classes modules comments inline docs commit messages

You don’t code for CPU

You don’t code for interpreter

You don’t code for compiler

You code for people

You code for other developers

You code for your future self

“Don’t code, write prose” Sławomir Sobótka

“Instead of imagining that our main task is to instruct a computer what to do, let us concentrate rather on explaining to human beings what we want a computer to do.” Donald E. Knuth

Comprehension

~70%

function a($b) { sort($b); $c = count($b); if ($c % 2 === 1) { return $b[($c - 1) / 2]; } else { return ($b[$c/2 - 1] + $b[$c/2]) / 2; } }

function median($pool) { sort($pool); $size = count($pool); if ($size % 2 === 1) { return $pool[($size - 1] / 2]; } else { return ($pool[$size/2 - 1] + $pool[$size/2]) / 2; } }

Self-documenting code

Programming is mapping from problem domain via intermediate domain into programming domain

Worst variable name

data

Second worst name?

data2

$total = $price * $qty; $total2 = $total - $discount; $total2 += $total * $taxrate; $total3 = $purchase_order_value + $available_credit; if ($total2 < $total3) { echo “You can’t afford this order.”; }

$order_total = $price * $qty $payable_total = $order_total - $discount $payable_total += $payable_total * $taxrate $available_funds = $purchase_order_value + $availble_credit if ($payable_total < $available_funds) { echo “You can’t afford this order.”; }

“No-one sets out to write legacy code” Rachel Willmer

Broken window theory

Code will decay

Design patterns

Misapplied Java design patterns are the root of all AbstractWordFactoryFactory(“evil”) anonymous HN comment

Naming conventions CamelCaseClass methodName someVariable CAPITAL_CONSTANT

syntax < semanthics

Bad name Does more that what is says Says more than what it does Does the opposite Contains more than what it says Says more than what it contains Contains the opposite

Common issues

Pseudo getter

get_data() with extra operations inside

get_create_object()

Alternatives fetch find lookup create calculate

Not really a boolean

is_active() function is_active() { if (cond) { return ‘false’; } return ‘true’; }

is_valid() function is_valid() { if (input_is_valid) { return true; } }

Plural / singular names function get_person() { return array(‘John Doe’, ‘Jane Doe’); } function get_employers() { return ‘John Doe’; }

Misleading docs

function get_lowest_price($user) { }

/** * Actually it returns the highest price. */ function get_lowest_price($user) { }

/** * Actually it returns the highest price. */ function get_lowest_price($user) { if ($user === null) { return _get_highest_price(); } else { return _get_lowest_price($user); } }

More than one responsibility

Abbreviations pos mod abs auth

Synonyms

<ThatThing>Manager UserManager StringManager ProductManager etc.

Alternatives Builder Writer Adapter Factory Handler Provider Converter

Magic numbers

$client = new GuzzleHttp\Client(); $url = ‘https://2019.phpcon.pl/’; $response = $client->request(‘GET’, $url); $response_code = $response->getStatusCode(); if ($response_code === 200) { echo ‘It works!’; } elseif ($response_code === 418) { // ??? }

$client = new GuzzleHttp\Client(); $url = ‘https://2019.phpcon.pl/’; $response = $client->request(‘GET’, $url); $response_code = $response->getStatusCode(); if ($response_code === StatusCode::OK) { echo ‘Website works!’; } elseif ($response_code === StatusCode::IM_A_TEAPOT) { echo ‘Would like a cup of tea?’; }

Useless comments /** * Returns the data. / function get_data() {} /* * Return maximum ID value from the database. */ function get_max_id_from_db() {}

Explain why why,, not what or how

“Code should have comments, but if your file is more than 25% comments, that’s a red flag: you may be explaining bad code” Adam Culp

Commit messages

Good practices

Define dictionary

Short names

Do not use negation

is_not_enabled() is_disabled()

Consistent names in code & docs

Single responsibility

Domain terms

Think about it

ASCII only $Δ = 1; ++$Δ; echo $Δ;

Tests!

Commit message

Good commit message Speeds up review process Helps write release notes Helps future maintainers

Short (50 chars or less) summary of changes More detailed explanatory text, if necessary. Wrap it to about 72 characters or so. In some contexts, the first line is treated as the subject of an email and the rest of the text as the body. The blank line separating the summary from the body is critical (unless you omit the body entirely); tools like rebase can get confused if you run the two together. Further paragraphs come after blank lines. - Bullet points are okay, too - Typically a hyphen or asterisk is used for the bullet, preceded by a single space, with blank lines in between, but conventions vary here

Agree on standards Use english, please

Boy Scout Rule

Practice

Improve vocabulary

Refactor

Code reviews Short, bite size, single logical change

Code ownership

Commit messages

Research papers https://www.cqse.eu/publications/2005-concise-and-consistent-naming.pdf http://www.cs.loyola.edu/~lawrie/papers/lawrieJese07.pdf https://www.researchgate.net/publication/224079441_Relating_Identifier_Naming_Flaws_a http://www.veneraarnaoudova.com/wp-content/uploads/2014/10/2014-EMSE-Arnaodova-e

thank you