Line length Open
Первая строка содержит объявление, вторая — определение. Объявление (англ. declaration) — это весть всему миру о том, что такая функция существует, вот её имя и вот типы, с которыми она работает. Определение (англ. definition) — это весть о том, что конкретно делает данная функция.- 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
В процессе работы Haskell-программы в памяти создаётся великое множество различных данных, ведь мы постоянно строим новые данные на основе уже имеющихся. За их своевременное уничтожение отвечает сборщик мусора (англ. garbage collector, GC), встраиваемый в программы компилятором GHC.- 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
мы тем самым приказываем: «Возьми значение `0.569` и перезапиши им то значение, которое уже содержалось в переменной `coeff` до этого». И перезаписывать это значение мы можем множество раз, а следовательно, мы вынуждены внимательно отслеживать текущее состояние переменной `coeff`, равно как и состояния всех остальных переменных в нашем коде.- 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
Оно разделено двойным двоеточием на две части: слева указано имя функции, справа — типы, с которыми эта функция работает, а именно типы аргументов и тип вычисленного, итогового значения. Как вы узнали из предыдущей главы, все данные в Haskell-программе имеют конкретный тип, а поскольку функция работает с данными, её объявление содержит типы этих данных. Типы разделены стрелками. Схематично это выглядит 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
мы просто объявляем: «Отныне значение `coeff` равно `0.569`, и так оно будет всегда». Вот почему в Haskell-коде символ `=` — это знак равенства в математическом смысле, и с присваиванием он не имеет ничего общего.- 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
Идею вы поняли: ищем крайнюю правую стрелку, и всё что левее от неё — то типы аргументов, а всё что правее — то тип вычисленного значения.- 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
мы объявляем следующее: «Отныне выражение `prod x y` равно выражению `x * y`». Мы можем безопасно заменить выражение `prod 2 5` выражением `2 * 5`, а выражение `prod 120 500` — выражением `120 * 500`, и при этом работа программы гарантированно останется неизменной.- 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
В мире Haskell нет места оператору присваивания. Впрочем, этот факт удивителен лишь на первый взгляд. Задумаемся: если каждая функция в конечном итоге представляет собою выражение, вычисляемое посредством применения каких-то других функций к каким-то другим аргументам, тогда нам просто не нужно ничего ничему присваивать.- 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
А теперь, дабы не мучить вас вопросами без ответов, мы начнём ближе знакомиться с Китами Haskell, и детали большой головоломки постепенно сложатся в красивую картину.- 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
Мы не можем работать с функцией, которая ничего не вычисляет. То есть аналога C-функции `void f(int i)` в Haskell быть не может, так как это противоречит математической природе. Однако мы можем работать с функцией, которая ничего не принимает, то есть с аналогом C-функции `int f(void)`. С такими функциями мы познакомимся в следующих 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
Вспомним, что присваивание (англ. assignment) пришло к нам из императивных языков. Императивное программирование (англ. imperative programming) — это направление в разработке, объединяющее несколько парадигм программирования, одной из которых является знаменитая объектно-ориентированная парадигма. В рамках этого направления программа воспринимается как набор инструкций, выполнение которых неразрывно связано с изменением состояния (англ. state) этой программы. Вот почему в императивных языках обязательно присутствует понятие «переменная» (англ. variable). А раз есть переменные — должен быть и оператор присваивания. Когда мы пишем:- 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
Определение тоже разделено на две части: слева от знака равенства — имя функции и имена аргументов (имена, а не типы), разделённые пробелами, а справа — выражение, составляющее суть функции, её содержимое. Иногда эти части называют «головой» и «телом»:- 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
Скажу больше: чистые функции не видят окружающий мир. Вообще. Они не могут вывести текст на консоль, их нельзя заставить обработать HTTP-запрос, они не умеют дружить с базой данных и прочесть файл они также неспособны. Они суть вещь в себе.- 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
Применение функции нам уже знакомо, осталось узнать про объявление и определение, без них использовать функцию не получится. Помните функцию `square`, возводящую свой единственный аргумент в квадрат? Вот как выглядит её объявление и определение:- 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
Такое объявление сообщает нам о том, что функция `square` принимает единственный аргумент типа `Int` и возвращает значение того же типа `Int`. Если же аргументов более одного, объявление просто вытягивается. Например, объявление функции `prod`, возвращающей произведение двух целочисленных аргументов, могло бы выглядеть 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
В предыдущей главе мы познакомились с функциями и выражениями, увидев близкую связь этих понятий. В этой главе мы познакомимся с функциями поближе, а также узнаем, что такое «чисто функциональный» язык и почему в нём нет места оператору присваивания.- 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
Уверен, вы удивлены. Как же можно написать реальную программу на языке, в котором нельзя изменять данные? Какой прок от этих чистых функций, если они не способны ни файл прочесть, ни запрос по сети отправить? Оказывается, прок есть, и на Haskell можно написать очень даже реальную программу. За примером далеко ходить не буду: сама эта книга построена с помощью программы, написанной на Haskell, о чём я подробнее расскажу в следующих 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
Обратите внимание, речь здесь идёт именно о знаке равенства, а никак не об операторе присваивания. Мы ничего не присваиваем, мы лишь декларируем равенство левой и правой частей. Когда мы пишем:- 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
Однако существует принципиально иной подход к разработке, а именно декларативное программирование (англ. declarative programming). Данное направление также включает в себя несколько парадигм, одной из которых является функциональная парадигма, нашедшая своё воплощение в Haskell. При этом подходе программа воспринимается уже не как набор инструкций, а как набор выражений. А поскольку выражения вычисляются путём применения функций к аргументам (то есть, по сути, к другим выражениям), там нет места ни переменным, ни оператору присваивания. Все данные в Haskell-программе, будучи созданными единожды, уже не могут быть изменены. Поэтому нам не нужен не только оператор присваивания, но и ключевое слово `const`. И когда в Haskell-коде мы пишем:- 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
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
- 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
- Exclude checks
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.