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Fix various issues and cleanup whitespace #9

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Fix various issues and cleanup whitespace #9

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49dae75
cleanup trailing spaces
catwell Nov 20, 2013
8997401
fixes #6, #7 and #8
catwell Nov 20, 2013
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89 changes: 57 additions & 32 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,7 @@ you find any mistakes or typos.

print(foo[0], bar[0]) -- => 9 9
print(foo[1], bar[1]) -- => 3 3
print(foo[2], bar[2]) -- => 2 2
print(foo[2], bar[2]) -- => 2 2
```

**[[⬆]](#TOC)**
Expand All @@ -95,7 +95,7 @@ you find any mistakes or typos.
```lua
-- bad
local player = {
attack = function()
attack = function()
-- ...stuff...
end
}
Expand All @@ -109,35 +109,60 @@ you find any mistakes or typos.
}
```

- Consider `nil` properties when selecting lengths.
A good idea is to store an `n` property on lists that contain the length
- The length operator does not work as you may expect on tables that
contain `nil`.
A good idea is to store an `n` property on lists that contain their length
(as noted in [Storing Nils in Tables](http://lua-users.org/wiki/StoringNilsInTables))

```lua
-- nils don't count
local list = {}
list[0] = nil
list[1] = "item"
list[2] = nil

print(#list) -- 0
print(select('#', list)) -- 1
print(#list) -- 1
```

```lua
local list = {}
list[1] = "item"
list[2] = nil
list[3] = "item"

print(#list) -- undefined result
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This should say that it returns 1 rather than the expected 3.

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With a given Lua implementation. But the definition in the language is even worse. In Lua 5.1:

any integer index n such that t[n] is not nil and t[n+1] is nil

So it could be 1 or 3.

In Lua 5.2 it is even clearer:

Unless a __len metamethod is given, the length of a table t is only defined if the table is a sequence, that is, the set of its positive numeric keys is equal to {1..n} for some integer n

So the operator could return anything. Or crash your program, for that matter. Actually I expect some later Lua implementations to raise an error in that situation.

Anyway, my point is: you cannot rely on it being 3 but you cannot rely on it being 1 either.

EDIT: If you think this undefined stuff is theoretical, guess what this prints:

print(#{1, 2, nil, 3})

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That's true; maybe expand it as result depends on Lua implementation, then?

I admit, I only tested it in Lua 5.1.5 and Luajit 2.0.2 to confirm.

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Yes, it depends on the implementation. And it is not consistent even on Lua 5.1.5. As I said in my edit above, if you put the hole just one step further it doesn't give the same answer:

Lua 5.1.5  Copyright (C) 1994-2012 Lua.org, PUC-Rio
> list = {}
> list[1] = "item"
> list[2] = "item"
> list[3] = nil
> list[4] = "item"
> =#list
4

If you are interested in the "why" see the implementation. Hint: binary search.

```

- The length operator always counts from 1. If you store values at negative
positions in a table (including 0) they will be ignored.

```lua
local list = {}
list[0] = "item"
list[1] = "item"

print(#list) -- 1
```

- When tables have functions, use `self` when referring to itself.

```lua
-- bad
local fullname = function(this)
return this.first_name + " " + this.last_name
end
local me = {
fullname = function(this)
return this.first_name + " " + this.last_name
end
fullname = fullname,
first_name = "Jack",
last_name = "Smith",
}

-- good
local fullname = function(self)
return self.first_name + " " + self.last_name
end
local me = {
fullname = function(self)
return self.first_name + " " + self.last_name
end
fullname = fullname,
first_name = "Jack",
last_name = "Smith",
}
```

Expand All @@ -161,7 +186,7 @@ you find any mistakes or typos.
local fullName = 'Bob ' .. self.lastName
```

- Strings longer than 80 characters should be written across multiple lines
- Strings longer than 80 characters should be written across multiple lines
using concatenation. This allows you to indent nicely.

```lua
Expand Down Expand Up @@ -219,7 +244,7 @@ you find any mistakes or typos.

```lua
-- bad
local function nope(name, options, arg)
local function nope(name, options, arg)
-- ...stuff...
end

Expand Down Expand Up @@ -281,7 +306,7 @@ you find any mistakes or typos.
age = 28
}

local function getProp(prop)
local function getProp(prop)
return luke[prop]
end

Expand Down Expand Up @@ -371,7 +396,7 @@ you find any mistakes or typos.
end
```

- Prefer *true* statements over *false* statements where it makes sense.
- Prefer *true* statements over *false* statements where it makes sense.
Prioritize truthy conditions when writing multiple conditions.

```lua
Expand Down Expand Up @@ -458,8 +483,8 @@ you find any mistakes or typos.
if test < 1 and do_complicated_function(test) == false or
seven == 8 and nine == 10 then

do_other_complicated_function()
return false
do_other_complicated_function()
return false
end
```

Expand All @@ -472,17 +497,17 @@ you find any mistakes or typos.

```lua
-- bad
function()
function()
∙∙∙∙local name
end

-- bad
function()
function()
∙local name
end

-- good
function()
function()
∙∙local name
end
```
Expand Down Expand Up @@ -513,14 +538,14 @@ you find any mistakes or typos.

```lua
-- bad
(function(global)
(function(global)
-- ...stuff...
end)(self)
```

```lua
-- good
(function(global)
(function(global)
-- ...stuff...
end)(self)

Expand All @@ -547,11 +572,11 @@ you find any mistakes or typos.
```lua
--bad
local thing = {1,2,3}
thing = {1 , 2 , 3}
thing = {1 ,2 ,3}
thing = { 1 , 2 , 3 }
thing = { 1 ,2 ,3 }

--good
local thing = {1, 2, 3}
local thing = { 1, 2, 3 }
```

- Add a line break after multiline blocks.
Expand Down Expand Up @@ -666,12 +691,12 @@ you find any mistakes or typos.

```lua
-- bad
local function q()
local function q()
-- ...stuff...
end

-- good
local function query()
local function query()
-- ..stuff..
end
```
Expand Down Expand Up @@ -763,7 +788,7 @@ you find any mistakes or typos.
## <a name='file-structrure'>File Structure</a>

- Files should be named in all lowercase.
- Lua files should be in a top-level `src` folder. The main library file should
- Lua files should be in a top-level `src` folder. The main library file should
be called `modulename.lua`.
- Rockspecs, license, readme, etc should be in the top level.
- Tests should be in a top-level spec folder.
Expand All @@ -789,7 +814,7 @@ you find any mistakes or typos.

## <a name='testing'>Testing</a>

- Use [busted](olivinelabs.com/busted) and write lots of tests in a /spec
- Use [busted](olivinelabs.com/busted) and write lots of tests in a /spec
folder. Separate tests by module.
- Use descriptive `describe` and `it` blocks so it's obvious to see what
precisely is failing.
Expand Down