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[Lua-love2d] Snake贪吃蛇

2017-07-31

mdgsf

lua

Lua

package.path = package.path .. ";E:\\Lua\\lualogging\\src\\?.lua"
require("logging")
require("logging.file")

function GetMicroTime()
    return love.timer.getTime() * 1000
end

-- This function is called exactly once at the beginning of the game.
function love.load()

    -- Init log
    logger = logging.file("Snake_%s.log", "%Y-%m-%d")
    logger:info("logging.file test")
    logger:debug("debug...")
    logger:error("error!")

    logger:info("Game Start.")

    -- Init images
    images = {}
    for idx, image in ipairs({'blank', 'body'}) do
        images[image] = love.graphics.newImage('images/' .. image .. '.png')
    end

    logger:info(images)

    -- Init Windows Size
    cellSize = 7

    gridXCount = 50
    gridYCount = 50

    WindowWidth = cellSize * gridXCount
    WindowHeight = cellSize * gridYCount

    logger:info("WindowWidth = " .. WindowWidth .. " WindowHeight = " .. WindowHeight)


    -- Init Speed, 1000ms one move.
    SnakeSpeed = 200
    LastTime = GetMicroTime()


    function GetOneBlankPosition()
        local BlankPosition = {}
        for x = 1, gridXCount do
            for y = 1, gridYCount do
                if grid[x][y].type == 0 then
                    table.insert(BlankPosition, {x, y})
                end
            end
        end

        return BlankPosition[love.math.random(#BlankPosition)]
    end

    function ShowGrid()
        for x = 1, gridXCount do
            local rowStr = string.format("%02d ", x)
            for y = 1, gridYCount do
                rowStr = rowStr .. grid[x][y].type .. " "
            end
            logger:info(rowStr)
        end
    end

    -- Init Grid
    function reset()
        logger:info("reset")

        grid = {}
        for x = 1, gridXCount do
            grid[x] = {}
            for y = 1, gridYCount do
                grid[x][y] = {
                    type = 0 -- 0:blank, 1:Snake Body, 2:Food
                }
            end
        end

        local RandX = love.math.random(5, gridXCount - 4)
        local RandY = love.math.random(5, gridYCount - 4)

        HeadDirection = love.math.random(4) -- 1:Up, 2:Right, 3:Down, 4:Left

        local TailX = RandX
        local TailY = RandY
        if HeadDirection == 1 then
            TailY = TailY + 1
        elseif HeadDirection == 2 then
            TailX = TailX - 1
        elseif HeadDirection == 3 then
            TailY = TailY - 1
        else
            TailX = TailX + 1
        end

        grid[RandX][RandY].type = 1
        grid[TailX][TailY].type = 1

        SnakeList = {}
        table.insert(SnakeList, {RandX, RandY})
        table.insert(SnakeList, {TailX, TailY})

        FoodPosition = GetOneBlankPosition()
        grid[FoodPosition[1]][FoodPosition[2]].type = 2

        ShowGrid()
    end

    reset()

end


-- Callback function used to update the state of the game every frame.
function love.update()

    currentTime = GetMicroTime()
    -- logger:info("currentTime = "..currentTime.." LastTime = "..LastTime)
    if currentTime - LastTime < SnakeSpeed then
        return
    end
    LastTime = currentTime

    local tail = SnakeList[1]
    local tailX = tail[1]
    local tailY = tail[2]

    local head = SnakeList[#SnakeList]
    local headX = head[1]
    local headY = head[2]

    local newNodeX = headX
    local newNodeY = headY

    if HeadDirection == 1 then
        newNodeX = newNodeX - 1
    elseif HeadDirection == 2 then
        newNodeY = newNodeY + 1
    elseif HeadDirection == 3 then
        newNodeX = newNodeX + 1
    else
        newNodeY = newNodeY - 1
    end

    logger:info("HeadDirection = "..HeadDirection)
    logger:info("tailX = "..tailX.." tailY = "..tailY)
    logger:info("headX = "..headX.." headY = "..headY)
    logger:info("newNodeX = "..newNodeX.." newNodeY = "..newNodeY.." type = "..grid[newNodeX][newNodeY].type)

    if grid[newNodeX][newNodeY].type == 0 then
        grid[tailX][tailY].type = 0
        grid[newNodeX][newNodeY].type = 1
        table.remove(SnakeList, 1)
        table.insert(SnakeList, {newNodeX, newNodeY})
    elseif grid[newNodeX][newNodeY].type == 1 then
        -- reset()
    elseif grid[newNodeX][newNodeY].type == 2 then
        grid[newNodeX][newNodeY].type = 1
        table.insert(SnakeList, {newNodeX, newNodeY})

        FoodPosition = GetOneBlankPosition()
        grid[FoodPosition[1]][FoodPosition[2]].type = 2
    end

end


-- Callback function used to draw on the screen every frame.
function love.draw()
    local function drawCell(image, x, y)
        love.graphics.draw(image, (y-1)*cellSize, (x-1)*cellSize)
    end

    for x = 1, gridXCount do
        for y = 1, gridYCount do
            if grid[x][y].type == 0 then
                drawCell(images.blank, x, y)
            else
                drawCell(images.body, x, y)
            end
        end
    end
end


function love.keypressed(key)
    logger:info("key = " .. key)

    if key == 'w' and HeadDirection ~= 3 then
        HeadDirection = 1
    elseif key == 'd' and HeadDirection ~= 4 then
        HeadDirection = 2
    elseif key == 's' and HeadDirection ~= 1 then
        HeadDirection = 3
    elseif key == 'a' and HeadDirection ~= 2 then
        HeadDirection = 4
    elseif key == 'space' then
        SnakeSpeed = 100
    else
        logger:info("Unknown key = " .. key)
        return
    end
end

function love.keyreleased(key)
    if key == 'space' then
        SnakeSpeed = 200
    end
end

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[Lua] 使用第3方库时，如何导入路径

2017-07-29

mdgsf

lua

Lua
如果是一个 *.LUA 的文件，里面用到了自己写的库，或者第三方写的库，但是你不想把它放到 lua 的安装目录里，则在代码里面可以指定require搜索的路径。
```
package.path = '/usr/local/share/lua/5.1/?.lua;/home/resty/?.lua;'    --搜索lua模块
package.cpath = '/usr/local/lib/lua/5.1/?.so;'        --搜索so模块

package.path = package.path .. ";E:\\Lua\\lualogging\\src\\?.lua"
```
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[Lua] logging日志库使用

2017-07-29

mdgsf

lua

Lua

https://github.com/Neopallium/lualogging

实例1

日志库就是 lualogging，放在 E:\Lua 这个目录下面。

package.path = package.path .. ";E:\\Lua\\lualogging\\src\\?.lua"

require("logging")

local logger = logging.new(
    function(self, level, message)
        print(level, message)
        return true
    end
)

-- logger:setLevel(logging.WARN)

logger:log(logging.INFO, "sending email")
logger:info("info log.")
logger:warn("warn log.")
logger:error("error log.")


local tab = { a = 1, b = 2, c = {1,2,3,4,5,6}}
logger:debug(tab)

logger:info("val1 = '%s', val2 = %d", "string value", 1234)

实例2 输出日志到文件中

package.path = package.path .. ";E:\\Lua\\lualogging\\src\\?.lua"
require("logging")
require("logging.file")

local logger = logging.file("test_%s.log", "%Y-%m-%d")

logger:info("logging.file test")
logger:debug("debug...")
logger:error("error!")

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[Lua] MetaTable and MetaMethod

2017-07-27

mdgsf

lua

Lua

比如，我们有两个分数：

fraction_a = {numerator=2, denominator=3}
fraction_b = {numerator=4, denominator=7}

我们想实现分数间的相加：2/3 + 4/7，我们如果要执行： fraction_a + fraction_b，会报错的。

所以，我们可以动用MetaTable，如下所示：

fraction_op={}
function fraction_op.__add(f1, f2)
    ret = {}
    ret.numerator = f1.numerator * f2.denominator + f2.numerator * f1.denominator
    ret.denominator = f1.denominator * f2.denominator
    return ret
end

为之前定义的两个table设置MetaTable：（其中的setmetatble是库函数）

setmetatable(fraction_a, fraction_op)
setmetatable(fraction_b, fraction_op)

于是你就可以这样干了：（调用的是fraction_op.__add()函数）

fraction_s = fraction_a + fraction_b

至于__add这是MetaMethod，这是Lua内建约定的，其它的还有如下的MetaMethod：

__add(a, b)                     对应表达式 a + b
__sub(a, b)                     对应表达式 a - b
__mul(a, b)                     对应表达式 a * b
__div(a, b)                     对应表达式 a / b
__mod(a, b)                     对应表达式 a % b
__pow(a, b)                     对应表达式 a ^ b
__unm(a)                        对应表达式 -a
__concat(a, b)                  对应表达式 a .. b
__len(a)                        对应表达式 #a
__eq(a, b)                      对应表达式 a == b
__lt(a, b)                      对应表达式 a < b
__le(a, b)                      对应表达式 a <= b
__index(a, b)                   对应表达式 a.b
__newindex(a, b, c)             对应表达式 a.b = c
__call(a, ...)                  对应表达式 a(...)

Set = {}
Set.mt = {} -- metatable for sets

function Set.new(t)
    t = t or {}
    local set = {}
    setmetatable(set, Set.mt)
    for _, l in ipairs(t) do
        set[l] = true
    end
    return set
end

function Set.union(a, b)

    if getmetatable(a) ~= Set.mt or
        getmetatable(b) ~= Set.mt then
        error("Attempt to 'add' a set with a not-set value", 2)
    end

    local res = Set.new()
    for k in pairs(a) do
        res[k] = true
    end
    for k in pairs(b) do
        res[k] = true
    end
    return res
end

function Set.intersection(a, b)
    local res = Set.new()
    for k in pairs(a) do
        res[k] = b[k]
    end
    return res
end

function Set.tostring(set)
    set = set or {}
    local s = "{"
    local sep = ""
    for e in pairs(set) do
        s = s .. sep .. e
        sep = ", "
    end
    return s .. "}"
end

function Set.print(s)
    print(Set.tostring(s))
end

-- 相加
Set.mt.__add = Set.union

-- 相乘，交集
Set.mt.__mul = Set.intersection


s1 = Set.new({10, 20, 30, 50})
s2 = Set.new({30, 1})
print(getmetatable(s1))
print(getmetatable(s2))

Set.print(s1)
Set.print(s2)

s3 = s1 + s2
Set.print(s3)

s = Set.new({1, 2, 3})
-- s = s + 8    -- table加上一个数字

Set.print(s1 * s2)

print("--------------")

print(s1)
print(s2)
-- print会自动调用__tostring，我们在这里修改了__tostring
Set.mt.__tostring = Set.tostring
print(s1)
print(s2)

参考链接：

http://coolshell.cn/articles/10739.html

http://book.luaer.cn/

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[Lua-pil] Bits and Bytes

2017-07-27

mdgsf

lua

Lua
读书笔记： Programming in Lua, 4th Edition.

Bitwise Operators
```
> string.format("%x", 0xff & 0xabcd) --> cd
> string.format("%x", 0xff | 0xabcd) --> abff
> string.format("%x", 0xaaaa ~ -1) --> ffffffffffff5555
> string.format("%x", ~0) --> ffffffffffffffff
```
Negative displacements shift in the other direction, that is, a » n is the same as a « -n:
```
> string.format("%x", 0xff << 12) --> ff000
> string.format("%x", 0xff >> -12) --> ff000
```
If the displacement is equal to or larger than the number of bits in the integer representation (64 in Standard Lua, 32 in Small Lua), the result is zero, as all bits are shifted out of the result:
```
> string.format("%x", -1 << 80) --> 0
```
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[Lua-pil] Object-Oriented Programming

2017-07-27

mdgsf

lua

Lua
读书笔记： Programming in Lua, 4th Edition.
```
Account = {
    balance = 0,
    withdraw = function(self, v)
        self.balance = self.balance - v
    end
}

function Account:deposit(v)
    self.balance = self.balance + v
end

-- 用.来调用函数的话，需要手动给self传值。
-- 用冒号来调用函数的话，可以省略self。
Account.deposit(Account, 200)
Account:deposit(200)

Account.withdraw(Account, 100)
Account:withdraw(100)
```
在上面的例子中，Account只是一个对象实例。

在C++中，一个类，可以生成多个对象实例。

在Lua中，没有类的概念，Lua是用metatable来模拟实现类的。

Classes

if we have two objects A and B, all we have to do to make B a prototype for A is this:
```
setmetatable(A, {__index = B})
```
After that, A looks up in B for any operation that it does not have.

Let us go back to our example of a bank account. To create other accounts with behavior similar to Account, we arrange for these new objects to inherit their operations from Account, using the __index metamethod.
```
local mt = {__index = Account}
function Account.new (o)
    o = o or {} -- create table if user does not provide one
    setmetatable(o, mt)
    return o
end
```
After this code, what happens when we create a new account and call a method on it, like this?
```
a = Account.new{balance = 0}
a:deposit(100.00)
```
When we create the new account, a, it will have mt as its metatable. When we call a:deposit(100.00), we are actually calling a.deposit(a, 100.00); the colon is only syntactic sugar. However, Lua cannot find a “deposit” entry in the table a; hence, Lua looks into the __index entry of the metatable. The situation now is more or less like this:
```
getmetatable(a).__index.deposit(a, 100.00)
```
The metatable of a is mt, and mt.__index is Account. Therefore, the previous expression evaluates to this one:
```
Account.deposit(a, 100.00)
```
That is, Lua calls the original deposit function, but passing a as the self parameter. So, the new account a inherited the function deposit from Account. By the same mechanism, it inherits all fields from Account.

We can make two small improvements on this scheme. The first one is that we do not need to create a new table for the metatable role; instead, we can use the Account table itself for that purpose. The second one is that we can use the colon syntax for the new method, too. With these two changes, method new becomes like this:
```
function Account:new (o)
    o = o or {}
    self.__index = self
    setmetatable(o, self)
    return o
end
```
Now, when we call Account:new(), the hidden parameter self gets Account as its value, we make Account.__index also equal to Account, and set Account as the metatable for the new object. It may seem that we do not gained much with the second change (the colon syntax); the advantage of using self will become apparent when we introduce class inheritance, in the next section.

Inheritance 继承
```
Account = {balance = 0}

function Account:new(o)
    o = o or {}
    self.__index = self
    setmetatable(o, self)
    return o
end

function Account:deposit(v)
    self.balance = self.balance + v
end

function Account:withdraw(v)
    if v > self.balance then error"insufficient funds" end
    self.balance = self.balance - v
end

SpecialAccount = Account:new()
s = SpecialAccount:new{limit = 1000.00}

function SpecialAccount:withdraw(v)
    if v - self.balance >= self.getLimit() then
        error"insufficient funds"
    end
    self.balance = self.balance - v
end

function SpecialAccount:getLimit()
    return self.limit or 0
end
```
就像一个链表一样，通过metatable一层一层向上找。
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55/97

Welcome to MDGSF's Blog!

[Lua-love2d] Snake贪吃蛇

[Lua] 使用第3方库时，如何导入路径

[Lua] logging日志库使用

实例1

实例2 输出日志到文件中

[Lua] MetaTable and MetaMethod

[Lua-pil] Bits and Bytes

Bitwise Operators

[Lua-pil] Object-Oriented Programming

Classes

Inheritance 继承