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authorMax <solomax2014@users.noreply.github.com>2014-08-07 17:53:03 +0400
committerMax <solomax2014@users.noreply.github.com>2014-08-07 17:53:03 +0400
commite110db4db65b3a3dcc21b2088bf6278334279065 (patch)
tree6d7c9a503fcf32d30d609a566820e696a8ccc628 /ru-ru/lua-ru.html.markdown
parent5a42a4e3010b22ab5dd7507b0d8997a7b5eb123b (diff)
1 part of Russian translation.
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+---
+language: lua
+filename: learnlua-ru.lua
+contributors:
+ - ["Tyler Neylon", "http://tylerneylon.com/"]
+translators:
+ - ["Max Solomonov", "https://vk.com/solomonovmaksim"]
+lang: ru-ru
+---
+
+```lua
+-- Два дефиса начинают однострочный комментарий.
+
+--[[
+ Добавление двух квадратных скобок
+ делает комментарий многострочным.
+--]]
+--------------------------------------------------------------------------------
+-- 1. Переменные, циклы и условия.
+--------------------------------------------------------------------------------
+
+num = 42 -- Все числа являются типом double.
+--[[
+ Не волнуйся, 64-битные double имеют 52 бита
+ для хранения именно целочисленных значений;
+ точность не является проблемой для
+ целочисленных значений, занимающих меньше
+ 52 бит.
+--]]
+
+s = 'walternate' -- Неизменные строки как в Python.
+t = "Двойные кавычки также приветствуются"
+u = [[ Двойные квадратные скобки
+ начинают и заканчивают
+ многострочные значения.]]
+t = nil -- Удаляет определение переменной t; Lua имеет мусорку.
+
+-- Циклы и условия имеют ключевые слова, такие как do/end:
+while num < 50 do
+ num = num + 1 -- Здесь нет ++ или += операторов.
+end
+
+-- Условие "если":
+if num > 40 then
+ print('больше 40')
+elseif s ~= 'walternate' then -- ~= обозначает "не равно".
+ -- Проверка равенства это == как в Python; ok для строк.
+ io.write('не больше 40\n') -- По умолчанию стандартный вывод.
+else
+ -- По умолчанию переменные являются глобальными.
+ thisIsGlobal = 5 -- Стиль CamelСase является общим.
+
+ -- Как сделать локальную переменную:
+ local line = io.read() -- Считывает введённую строку.
+
+ -- Конкатенация строк использует .. оператор:
+ print('Зима пришла, ' .. line)
+end
+
+-- Неопределённые переменные возвращают nil.
+-- Этот пример не является ошибочным:
+foo = anUnknownVariable -- Теперь foo = nil.
+
+aBoolValue = false
+
+-- Только значения nil и false являются ложными; 0 и '' являются истинными!
+if not aBoolValue then print('это значение ложно') end
+
+--[[
+ Для 'or' и 'and' действует принцип "какой оператор дальше,
+ тот и применается". Это действует аналогично a?b:c
+ операторам в C/js:
+--]]
+ans = aBoolValue and 'yes' or 'no' --> 'no'
+
+karlSum = 0
+for i = 1, 100 do -- The range includes both ends.
+ karlSum = karlSum + i
+end
+
+-- Use "100, 1, -1" as the range to count down:
+fredSum = 0
+for j = 100, 1, -1 do fredSum = fredSum + j end
+
+-- In general, the range is begin, end[, step].
+
+-- Another loop construct:
+repeat
+ print('the way of the future')
+ num = num - 1
+until num == 0
+
+--------------------------------------------------------------------------------
+-- 2. Functions.
+--------------------------------------------------------------------------------
+
+function fib(n)
+ if n < 2 then return n end
+ return fib(n - 2) + fib(n - 1)
+end
+
+-- Closures and anonymous functions are ok:
+function adder(x)
+ -- The returned function is created when adder is called, and remembers the
+ -- value of x:
+ return function (y) return x + y end
+end
+a1 = adder(9)
+a2 = adder(36)
+print(a1(16)) --> 25
+print(a2(64)) --> 100
+
+-- Returns, func calls, and assignments all work with lists that may be
+-- mismatched in length. Unmatched receivers are nil; unmatched senders are
+-- discarded.
+
+x, y, z = 1, 2, 3, 4
+-- Now x = 1, y = 2, z = 3, and 4 is thrown away.
+
+function bar(a, b, c)
+ print(a, b, c)
+ return 4, 8, 15, 16, 23, 42
+end
+
+x, y = bar('zaphod') --> prints "zaphod nil nil"
+-- Now x = 4, y = 8, values 15..42 are discarded.
+
+-- Functions are first-class, may be local/global. These are the same:
+function f(x) return x * x end
+f = function (x) return x * x end
+
+-- And so are these:
+local function g(x) return math.sin(x) end
+local g = function(x) return math.sin(x) end
+-- Equivalent to local function g(x)..., except referring to g in the function
+-- body won't work as expected.
+local g; g = function (x) return math.sin(x) end
+-- the 'local g' decl makes g-self-references ok.
+
+-- Trig funcs work in radians, by the way.
+
+-- Calls with one string param don't need parens:
+print 'hello' -- Works fine.
+
+-- Calls with one table param don't need parens either (more on tables below):
+print {} -- Works fine too.
+
+--------------------------------------------------------------------------------
+-- 3. Tables.
+--------------------------------------------------------------------------------
+
+-- Tables = Lua's only compound data structure; they are associative arrays.
+-- Similar to php arrays or js objects, they are hash-lookup dicts that can
+-- also be used as lists.
+
+-- Using tables as dictionaries / maps:
+
+-- Dict literals have string keys by default:
+t = {key1 = 'value1', key2 = false}
+
+-- String keys can use js-like dot notation:
+print(t.key1) -- Prints 'value1'.
+t.newKey = {} -- Adds a new key/value pair.
+t.key2 = nil -- Removes key2 from the table.
+
+-- Literal notation for any (non-nil) value as key:
+u = {['@!#'] = 'qbert', [{}] = 1729, [6.28] = 'tau'}
+print(u[6.28]) -- prints "tau"
+
+-- Key matching is basically by value for numbers and strings, but by identity
+-- for tables.
+a = u['@!#'] -- Now a = 'qbert'.
+b = u[{}] -- We might expect 1729, but it's nil:
+-- b = nil since the lookup fails. It fails because the key we used is not the
+-- same object as the one used to store the original value. So strings &
+-- numbers are more portable keys.
+
+-- A one-table-param function call needs no parens:
+function h(x) print(x.key1) end
+h{key1 = 'Sonmi~451'} -- Prints 'Sonmi~451'.
+
+for key, val in pairs(u) do -- Table iteration.
+ print(key, val)
+end
+
+-- _G is a special table of all globals.
+print(_G['_G'] == _G) -- Prints 'true'.
+
+-- Using tables as lists / arrays:
+
+-- List literals implicitly set up int keys:
+v = {'value1', 'value2', 1.21, 'gigawatts'}
+for i = 1, #v do -- #v is the size of v for lists.
+ print(v[i]) -- Indices start at 1 !! SO CRAZY!
+end
+-- A 'list' is not a real type. v is just a table with consecutive integer
+-- keys, treated as a list.
+
+--------------------------------------------------------------------------------
+-- 3.1 Metatables and metamethods.
+--------------------------------------------------------------------------------
+
+-- A table can have a metatable that gives the table operator-overloadish
+-- behavior. Later we'll see how metatables support js-prototypey behavior.
+
+f1 = {a = 1, b = 2} -- Represents the fraction a/b.
+f2 = {a = 2, b = 3}
+
+-- This would fail:
+-- s = f1 + f2
+
+metafraction = {}
+function metafraction.__add(f1, f2)
+ local sum = {}
+ sum.b = f1.b * f2.b
+ sum.a = f1.a * f2.b + f2.a * f1.b
+ return sum
+end
+
+setmetatable(f1, metafraction)
+setmetatable(f2, metafraction)
+
+s = f1 + f2 -- call __add(f1, f2) on f1's metatable
+
+-- f1, f2 have no key for their metatable, unlike prototypes in js, so you must
+-- retrieve it as in getmetatable(f1). The metatable is a normal table with
+-- keys that Lua knows about, like __add.
+
+-- But the next line fails since s has no metatable:
+-- t = s + s
+-- Class-like patterns given below would fix this.
+
+-- An __index on a metatable overloads dot lookups:
+defaultFavs = {animal = 'gru', food = 'donuts'}
+myFavs = {food = 'pizza'}
+setmetatable(myFavs, {__index = defaultFavs})
+eatenBy = myFavs.animal -- works! thanks, metatable
+
+--------------------------------------------------------------------------------
+-- Direct table lookups that fail will retry using the metatable's __index
+-- value, and this recurses.
+
+-- An __index value can also be a function(tbl, key) for more customized
+-- lookups.
+
+-- Values of __index,add, .. are called metamethods.
+-- Full list. Here a is a table with the metamethod.
+
+-- __add(a, b) for a + b
+-- __sub(a, b) for a - b
+-- __mul(a, b) for a * b
+-- __div(a, b) for a / b
+-- __mod(a, b) for a % b
+-- __pow(a, b) for a ^ b
+-- __unm(a) for -a
+-- __concat(a, b) for a .. b
+-- __len(a) for #a
+-- __eq(a, b) for a == b
+-- __lt(a, b) for a < b
+-- __le(a, b) for a <= b
+-- __index(a, b) <fn or a table> for a.b
+-- __newindex(a, b, c) for a.b = c
+-- __call(a, ...) for a(...)
+
+--------------------------------------------------------------------------------
+-- 3.2 Class-like tables and inheritance.
+--------------------------------------------------------------------------------
+
+-- Classes aren't built in; there are different ways to make them using
+-- tables and metatables.
+
+-- Explanation for this example is below it.
+
+Dog = {} -- 1.
+
+function Dog:new() -- 2.
+ local newObj = {sound = 'woof'} -- 3.
+ self.__index = self -- 4.
+ return setmetatable(newObj, self) -- 5.
+end
+
+function Dog:makeSound() -- 6.
+ print('I say ' .. self.sound)
+end
+
+mrDog = Dog:new() -- 7.
+mrDog:makeSound() -- 'I say woof' -- 8.
+
+-- 1. Dog acts like a class; it's really a table.
+-- 2. "function tablename:fn(...)" is the same as
+-- "function tablename.fn(self, ...)", The : just adds a first arg called
+-- self. Read 7 & 8 below for how self gets its value.
+-- 3. newObj will be an instance of class Dog.
+-- 4. "self" is the class being instantiated. Often self = Dog, but inheritance
+-- can change it. newObj gets self's functions when we set both newObj's
+-- metatable and self's __index to self.
+-- 5. Reminder: setmetatable returns its first arg.
+-- 6. The : works as in 2, but this time we expect self to be an instance
+-- instead of a class.
+-- 7. Same as Dog.new(Dog), so self = Dog in new().
+-- 8. Same as mrDog.makeSound(mrDog); self = mrDog.
+
+--------------------------------------------------------------------------------
+
+-- Inheritance example:
+
+LoudDog = Dog:new() -- 1.
+
+function LoudDog:makeSound()
+ local s = self.sound .. ' ' -- 2.
+ print(s .. s .. s)
+end
+
+seymour = LoudDog:new() -- 3.
+seymour:makeSound() -- 'woof woof woof' -- 4.
+
+--------------------------------------------------------------------------------
+-- 1. LoudDog gets Dog's methods and variables.
+-- 2. self has a 'sound' key from new(), see 3.
+-- 3. Same as "LoudDog.new(LoudDog)", and converted to "Dog.new(LoudDog)" as
+-- LoudDog has no 'new' key, but does have "__index = Dog" on its metatable.
+-- Result: seymour's metatable is LoudDog, and "LoudDog.__index = Dog". So
+-- seymour.key will equal seymour.key, LoudDog.key, Dog.key, whichever
+-- table is the first with the given key.
+-- 4. The 'makeSound' key is found in LoudDog; this is the same as
+-- "LoudDog.makeSound(seymour)".
+
+-- If needed, a subclass's new() is like the base's:
+function LoudDog:new()
+ local newObj = {}
+ -- set up newObj
+ self.__index = self
+ return setmetatable(newObj, self)
+end
+
+--------------------------------------------------------------------------------
+-- 4. Modules.
+--------------------------------------------------------------------------------
+
+
+--[[ I'm commenting out this section so the rest of this script remains
+-- runnable.
+```
+
+```lua
+-- Suppose the file mod.lua looks like this:
+local M = {}
+
+local function sayMyName()
+ print('Hrunkner')
+end
+
+function M.sayHello()
+ print('Why hello there')
+ sayMyName()
+end
+
+return M
+
+-- Another file can use mod.lua's functionality:
+local mod = require('mod') -- Run the file mod.lua.
+
+-- require is the standard way to include modules.
+-- require acts like: (if not cached; see below)
+local mod = (function ()
+ <contents of mod.lua>
+end)()
+-- It's like mod.lua is a function body, so that locals inside mod.lua are
+-- invisible outside it.
+
+-- This works because mod here = M in mod.lua:
+mod.sayHello() -- Says hello to Hrunkner.
+
+-- This is wrong; sayMyName only exists in mod.lua:
+mod.sayMyName() -- error
+
+-- require's return values are cached so a file is run at most once, even when
+-- require'd many times.
+
+-- Suppose mod2.lua contains "print('Hi!')".
+local a = require('mod2') -- Prints Hi!
+local b = require('mod2') -- Doesn't print; a=b.
+
+-- dofile is like require without caching:
+dofile('mod2') --> Hi!
+dofile('mod2') --> Hi! (runs again, unlike require)
+
+-- loadfile loads a lua file but doesn't run it yet.
+f = loadfile('mod2') -- Calling f() runs mod2.lua.
+
+-- loadstring is loadfile for strings.
+g = loadstring('print(343)') -- Returns a function.
+g() -- Prints out 343; nothing printed before now.
+
+--]]
+
+```
+## References
+
+I was excited to learn Lua so I could make games
+with the <a href="http://love2d.org/">Love 2D game engine</a>. That's the why.
+
+I started with <a href="http://nova-fusion.com/2012/08/27/lua-for-programmers-part-1/">BlackBulletIV's Lua for programmers</a>.
+Next I read the official <a href="http://www.lua.org/pil/contents.html">Programming in Lua</a> book.
+That's the how.
+
+It might be helpful to check out the <a href="http://lua-users.org/files/wiki_insecure/users/thomasl/luarefv51.pdf">Lua short
+reference</a> on lua-users.org.
+
+The main topics not covered are standard libraries:
+
+* <a href="http://lua-users.org/wiki/StringLibraryTutorial">string library</a>
+* <a href="http://lua-users.org/wiki/TableLibraryTutorial">table library</a>
+* <a href="http://lua-users.org/wiki/MathLibraryTutorial">math library</a>
+* <a href="http://lua-users.org/wiki/IoLibraryTutorial">io library</a>
+* <a href="http://lua-users.org/wiki/OsLibraryTutorial">os library</a>
+
+By the way, the entire file is valid Lua; save it
+as learn.lua and run it with "lua learn.lua" !
+
+This was first written for tylerneylon.com, and is
+also available as a <a href="https://gist.github.com/tylerneylon/5853042">github gist</a>. Have fun with Lua!