diff --git a/lua.html.markdown b/lua.html.markdown
index 32174a81..0a7c4f00 100644
--- a/lua.html.markdown
+++ b/lua.html.markdown
@@ -12,13 +12,15 @@ filename: learnlua.lua
Adding two ['s and ]'s makes it a
multi-line comment.
--]]
---------------------------------------------------------------------------------
+
+----------------------------------------------------
-- 1. Variables and flow control.
---------------------------------------------------------------------------------
+----------------------------------------------------
num = 42 -- All numbers are doubles.
--- Don't freak out, 64-bit doubles have 52 bits for storing exact int
--- values; machine precision is not a problem for ints that need < 52 bits.
+-- Don't freak out, 64-bit doubles have 52 bits for
+-- storing exact int values; machine precision is
+-- not a problem for ints that need < 52 bits.
s = 'walternate' -- Immutable strings like Python.
t = "double-quotes are also fine"
@@ -58,15 +60,10 @@ aBoolValue = false
-- Only nil and false are falsy; 0 and '' are true!
if not aBoolValue then print('twas false') end
--- 'or' and 'and' are short-circuited. This is similar to the a?b:c operator
--- in C/js:
+-- 'or' and 'and' are short-circuited.
+-- This is similar to the a?b:c operator in C/js:
ans = aBoolValue and 'yes' or 'no' --> 'no'
--- BEWARE: this only acts as a ternary if the value returned when the condition
--- evaluates to true is not `false` or Nil
-iAmNotFalse = (not aBoolValue) and false or true --> true
-iAmAlsoNotFalse = (not aBoolValue) and true or false --> true
-
karlSum = 0
for i = 1, 100 do -- The range includes both ends.
karlSum = karlSum + i
@@ -84,19 +81,20 @@ repeat
num = num - 1
until num == 0
---------------------------------------------------------------------------------
+
+----------------------------------------------------
-- 2. Functions.
---------------------------------------------------------------------------------
+----------------------------------------------------
function fib(n)
- if n < 2 then return n end
+ if n < 2 then return 1 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:
+ -- 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)
@@ -104,9 +102,10 @@ 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.
+-- 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.
@@ -119,15 +118,13 @@ 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:
+-- 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.
@@ -136,16 +133,15 @@ local g; g = function (x) return math.sin(x) end
-- 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.
+-- 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:
@@ -161,13 +157,14 @@ t.key2 = nil -- Removes key2 from the table.
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.
+-- 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.
+-- 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
@@ -187,15 +184,16 @@ 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.
+-- 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
--- behaviour. Later we'll see how metatables support js-prototype behaviour.
+-- 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}
@@ -205,7 +203,7 @@ f2 = {a = 2, b = 3}
metafraction = {}
function metafraction.__add(f1, f2)
- local sum = {}
+ sum = {}
sum.b = f1.b * f2.b
sum.a = f1.a * f2.b + f2.a * f1.b
return sum
@@ -216,9 +214,10 @@ 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.
+-- 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
@@ -230,12 +229,11 @@ 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.
+-- 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.
+-- 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.
@@ -256,19 +254,19 @@ eatenBy = myFavs.animal -- works! thanks, metatable
-- __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.
+-- 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.
+ newObj = {sound = 'woof'} -- 3.
self.__index = self -- 4.
return setmetatable(newObj, self) -- 5.
end
@@ -281,59 +279,62 @@ 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.
+-- 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.
+-- 4. self = 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.
+-- 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.
+ 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
+-- 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 = LoudDog. So seymour.key will
+-- = 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)".
+-- 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 = {}
+ 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.
+--[[ I'm commenting out this section so the rest of
+-- this script remains runnable.
```
```lua
@@ -359,8 +360,8 @@ local mod = require('mod') -- Run the file mod.lua.
local mod = (function ()
end)()
--- It's like mod.lua is a function body, so that locals inside mod.lua are
--- invisible outside it.
+-- 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.
@@ -368,19 +369,19 @@ 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.
+-- 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)
+dofile('mod2.lua') --> Hi!
+dofile('mod2.lua') --> Hi! (runs it again)
-- loadfile loads a lua file but doesn't run it yet.
-f = loadfile('mod2') -- Calling f() runs mod2.lua.
+f = loadfile('mod2.lua') -- Call f() to run it.
-- loadstring is loadfile for strings.
g = loadstring('print(343)') -- Returns a function.