Lua5.0 示例程序抽样
Lua5.0 的 test 目录里是一些 Lua 示例程序，有些挺有意思的，这里拿出来看看。
简单的介绍在 README 文件里有描述。
这些程序应该就是原作者的团队写的，有的程序的含金量很高，也很有意思。
比如协程的使用（sieve.lua），比如生命游戏（life.lua），比如排序（sort.lua），比如几个算法。
看一下排序
-- two implementations of a sort function
-- this is an example only. Lua has now a built-in function "sort"
-- extracted from Programming Pearls, page 110
function qsort(x,l,u,f)
if l<u then
local m=math.random(u-(l-1))+l-1-- choose a random pivot in range l..u
x[l],x[m]=x[m],x[l] -- swap pivot to first position
local t=x[l] -- pivot value
m=l
local i=l+1
while i<=u do
-- invariant: x[l+1..m] < t <= x[m+1..i-1]
if f(x[i],t) then
m=m+1
x[m],x[i]=x[i],x[m] -- swap x[i] and x[m]
end
i=i+1
end
x[l],x[m]=x[m],x[l] -- swap pivot to a valid place
-- x[l+1..m-1] < x[m] <= x[m+1..u]
qsort(x,l,m-1,f)
qsort(x,m+1,u,f)
end
end
function selectionsort(x,n,f)
local i=1
while i<=n do
local m,j=i,i+1
while j<=n do
if f(x[j],x[m]) then m=j end
j=j+1
end
x[i],x[m]=x[m],x[i] -- swap x[i] and x[m]
i=i+1
end
end
function show(m,x)
io.write(m,"\n\t")
local i=1
while x[i] do
io.write(x[i])
i=i+1
if x[i] then io.write(",") end
end
io.write("\n")
end
function testsorts(x)
local n=1
while x[n] do n=n+1 end; n=n-1 -- count elements
show("original",x)
qsort(x,1,n,function (x,y) return x<y end)
show("after quicksort",x)
selectionsort(x,n,function (x,y) return x>y end)
show("after reverse selection sort",x)
qsort(x,1,n,function (x,y) return x<y end)
show("after quicksort again",x)
end
-- array to be sorted
x={"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"}
testsorts(x)
有一个快速排序和一个选择排序。
代码说明一切，不做过多解释。
看一下一个闭包的使用。
-- function closures are powerful -- traditional fixed-point operator from functional programming Y = function (g) local a = function (f) return f(f) end return a(function (f) return g(function (x) local c=f(f) return c(x) end) end) end -- factorial without recursion F = function (f) return function (n) if n == 0 then return 1 else return n*f(n-1) end end end factorial = Y(F) -- factorial is the fixed point of F -- now test it function test(x) io.write(x,"! = ",factorial(x),"\n") end for n=0,16 do test(n) end
非递归的求阶乘，这里的 Y combinator 很是漂亮。
说明了 Lua 的函数式编程能力。
关于 Y combinator 的相关描述，这里有一篇写的很好的文章，感兴趣的可以看一下。
http://blog.csdn.net/pongba/article/details/1336028
标题叫做： 康托尔、哥德尔、图灵——永恒的金色对角线
etc 目录里也有几个实用小程序，比如 bin2c.c 。看一下 README 里的介绍：
bin2c.c
This program converts files to byte arrays that are automatically run
with lua_dobuffer. This allows C programs to include all necessary Lua
code, even in precompiled form. Even if the code is included in source
form, bin2c is useful because it avoids the hassle of having to quote
special characters in C strings.
Example of usage: Run bin2c file1 file2 ... > init.h. Then, in your
C program, just do #include "init.h" anywhere in the *body* of a
function. This will be equivalent to calling
lua_dofile(L,"file1"); lua_dofile(L,"file2"); ...
Note that the Lua state is called "L". If you use a different name,
say "mystate", just #define L mystate before you #include "init.h".
简单地说，这个程序可以把一个文件转换为字节流。保存到一个大大的字节数组里。
使用的时候调用 lua_dobuffer 即可。