Showing 612 of 612 total issues
Line length Open
Мы знаем, что у всех данных в Haskell-программе обязательно есть какой-то тип, внимательно проверяемый на этапе компиляции. Вопрос: какой тип у выражения `mul` из предыдущего примера?- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Dollar signs used before commands without showing output Open
```bash- Read upRead up
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MD014 - Dollar signs used before commands without showing output
Tags: code
Aliases: commands-show-output
This rule is triggered when there are code blocks showing shell commands to be typed, and the shell commands are preceded by dollar signs ($):
$ ls
$ cat foo
$ less barThe dollar signs are unnecessary in the above situation, and should not be included:
ls
cat foo
less barHowever, an exception is made when there is a need to distinguish between typed commands and command output, as in the following example:
$ ls
foo bar
$ cat foo
Hello world
$ cat bar
bazRationale: it is easier to copy and paste and less noisy if the dollar signs are omitted when they are not needed. See http://www.cirosantilli.com/markdown-styleguide/#dollar-signs-in-shell-code for more information.
Line length Open
В далёких 1930-х молодой американский математик [Алонзо Чёрч](https://en.wikipedia.org/wiki/Alonzo_Church) задался вопросом о том, что значит «вычислить» что-либо. Плодом его размышлений явилась система для формализации понятия «вычисление», и назвал он эту систему «лямбда-исчислением» (англ. lambda calculus, по имени греческой буквы `λ`). В основе этой системы лежит лямбда-функция, которую в некотором смысле можно считать «матерью функционального программирования» в целом и Haskell в частности. Далее буду называть её ЛФ.- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Погодите, скажете вы, но ведь это же объявление функции! Совершенно верно: объявление функции — это и есть указание её типа. Помните, когда мы впервые познакомились с функцией, я уточнил, что её объявление разделено двойным двоеточием? Так вот это двойное двоеточие и представляет собой указание типа:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Теперь выражения `containsAtSign` и `endsWithCom` приравнены к ЛФ от одного аргумента. В этом случае мы не указываем тип этих выражений. Впрочем, если очень хочется, можно и указать:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Это наша старая знакомая, функция `square`. Когда она будет применена к значению типа `Int`, тип аргумента будет выведен автоматически как `Int`.- Read upRead up
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MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Haskell — чисто функциональный (англ. purely functional) язык. Чисто функциональным он называется потому, что центральное место в нём уделено чистой функции (англ. pure function). А чистой называется такая функция, которая предельно честна с нами: её выходное значение всецело определяется её аргументами и более ничем. Это и есть функция в математическом смысле. Вспомним функцию `prod`: когда на входе числа `10` и `20` — на выходе всегда будет `200`, и ничто не способно помешать этому. Функция `prod` является чистой, а потому характеризуется отсутствием побочных эффектов (англ. side effects): она не способна сделать ничего, кроме как вернуть произведение двух своих аргументов. Именно поэтому чистая функция предельно надёжна, ведь она не может преподнести нам никаких сюрпризов.- Read upRead up
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MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Это — две функции, которые мы определили прямо в `where`-секции, поэтому они существуют только для основного выражения функции `validComEmail`. С простыми функциями так поступают очень часто: где она нужна, там её и определяют. Мы могли бы написать и более явно:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Любой, кто знаком с веб-разработкой, мгновенно узнает в этом коде HTML. Это [кусочек кода](https://github.com/denisshevchenko/ohaskell.guide/blob/master/src/CreateHtmlTemplates.hs#L56), строящего HTML-шаблон для веб-варианта данной книги. То что вы видите — это совершенно легальный Haskell-код, в процессе работы которого генерируется реальный HTML: тег `<div>` с классом `nav-wrapper`, внутри которого лежит `<a>`-ссылка с двумя классами, корневым адресом и внутренним текстом `#ohaskell`.- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Шли 30-е годы прошлого века, компьютеров не было, и все научные работы набирались на печатных машинках. В первоначальном варианте, дабы выделять имя аргумента ЛФ, Чёрч ставил над именем аргумента символ, похожий на `^`. Но когда он сдавал работу наборщику, то вспомнил, что печатная машинка не сможет воспроизвести такой символ над буквой. Тогда он вынес эту «крышу» перед именем аргумента, и получилось что-то наподобие:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Trailing punctuation in header Open
## «Присваивание? Не, не слышал…»- Read upRead up
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MD026 - Trailing punctuation in header
Tags: headers
Aliases: no-trailing-punctuation
Parameters: punctuation (string; default ".,;:!?")
This rule is triggered on any header that has a punctuation character as the last character in the line:
# This is a header.To fix this, remove any trailing punctuation:
# This is a headerNote: The punctuation parameter can be used to specify what characters class
as punctuation at the end of the header. For example, you can set it to
'.,;:!' to allow headers with question marks in them, such as might be used
in an FAQ.
Trailing punctuation in header Open
## Зачем это нужно?- Read upRead up
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MD026 - Trailing punctuation in header
Tags: headers
Aliases: no-trailing-punctuation
Parameters: punctuation (string; default ".,;:!?")
This rule is triggered on any header that has a punctuation character as the last character in the line:
# This is a header.To fix this, remove any trailing punctuation:
# This is a headerNote: The punctuation parameter can be used to specify what characters class
as punctuation at the end of the header. For example, you can set it to
'.,;:!' to allow headers with question marks in them, such as might be used
in an FAQ.
Line length Open
Почти все ASCII-символы (а также их всевозможные комбинации) можно использовать в качестве операторов в Haskell. Это даёт нам широкие возможности для реализации различных EDSL (англ. Embedded Domain Specific Language), своего рода «языков в языке». Вот пример:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Идентификаторы `div`, `class_` и `href` — это имена функций, а символы `!` и `$` — это операторы, записанные в инфиксной форме. Самое главное, что для понимания этого кода нам абсолютно необязательно знать, где определены все эти функции/операторы и как они работают. Это важная мысль, которую я неоднократно буду повторять в последующих главах:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Функция `makeAlias` даёт нам пару из хоста и имени. Но что это за странная запись возле уже знакомого нам слова `let`? Это промежуточное выражение, но выражение хитрое, образованное через паттерн матчинг. Чтобы было понятнее, сначала перепишем функцию без него:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Пожалуй, ничего проще придумать нельзя: на входе два аргумента, на выходе — двухэлементный кортеж с этими аргументами. Двухэлементный кортеж называют ещё парой (англ. pair). И хотя кортеж может содержать сколько угодно элементов, на практике именно пары встречаются чаще всего.- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
До тех пор, пока результат вычисления никому не нужен, оно не производится. Однако даже тогда, когда результат кому-то понадобился, вычисление происходит не до конца. Помните, выше я сказал, что при жадной модели вычисления выражение, являющееся аргументом, вычисляется «полностью»? А вот при ленивой модели мы вычисляем выражение лишь настолько, насколько это необходимо. Как вышеупомянутый ребёнок, убирающий игрушки в комнате, убирает их вовсе не до конца, а лишь до такой степени, чтобы его не ругали родители.- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Обратите внимание, насколько легко создаётся кортеж. Причина тому — уже знакомый нам паттерн матчинг:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Необычного вида оператор `!!` извлекает из списка элемент по индексу, в данном случае нас интересует второй по счёту элемент. Теперь нам уже недостаточно просто сформировать список, нам действительно нужен его второй элемент, иначе как бы мы смогли вывести его на консоль? В этом случае выражение `4 * 12.003` будет вычислено до своей окончательной, нормальной формы, а результат этого вычисления ляжет вторым элементом списка, вот так:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.
Line length Open
Был добавлен идентификатор заболевания. И всё бы хорошо, но внести изменения в функцию `patientEmail` мы забыли:- Read upRead up
- Exclude checks
MD013 - Line length
Tags: line_length
Aliases: line-length Parameters: linelength, codeblocks, tables (number; default 80, boolean; default true)
This rule is triggered when there are lines that are longer than the configured line length (default: 80 characters). To fix this, split the line up into multiple lines.
This rule has an exception where there is no whitespace beyond the configured line length. This allows you to still include items such as long URLs without being forced to break them in the middle.
You also have the option to exclude this rule for code blocks and tables. To
do this, set the code_blocks and/or tables parameters to false.
Code blocks are included in this rule by default since it is often a requirement for document readability, and tentatively compatible with code rules. Still, some languages do not lend themselves to short lines.