Lua Getting started with Lua Executing Lua programs
Example
Usually, Lua is being shipped with two binaries:
lua- standalone interpreter and interactive shellluac- bytecode compiler
Lets say we have an example program (bottles_of_mate.lua) like this:
local string = require "string"
function bottle_take(bottles_available)
local count_str = "%d bottles of mate on the wall."
local take_str = "Take one down, pass it around, " .. count_str
local end_str = "Oh noes, " .. count_str
local buy_str = "Get some from the store, " .. count_str
local bottles_left = 0
if bottles_available > 0 then
print(string.format(count_str, bottles_available))
bottles_left = bottles_available - 1
print(string.format(take_str, bottles_left))
else
print(string.format(end_str, bottles_available))
bottles_left = 99
print(string.format(buy_str, bottles_left))
end
return bottles_left
end
local bottle_count = 99
while true do
bottle_count = bottle_take(bottle_count)
end
The program itself can be ran by executing following on Your shell:
$ lua bottles_of_mate.lua
Output should look like this, running in the endless loop:
Get some from the store, 99 bottles of mate on the wall.
99 bottles of mate on the wall.
Take one down, pass it around, 98 bottles of mate on the wall.
98 bottles of mate on the wall.
Take one down, pass it around, 97 bottles of mate on the wall.
97 bottles of mate on the wall.
...
...
3 bottles of mate on the wall.
Take one down, pass it around, 2 bottles of mate on the wall.
2 bottles of mate on the wall.
Take one down, pass it around, 1 bottles of mate on the wall.
1 bottles of mate on the wall.
Take one down, pass it around, 0 bottles of mate on the wall.
Oh noes, 0 bottles of mate on the wall.
Get some from the store, 99 bottles of mate on the wall.
99 bottles of mate on the wall.
Take one down, pass it around, 98 bottles of mate on the wall.
...
You can compile the program into Lua's bytecode by executing following on Your shell:
$ luac bottles_of_mate.lua -o bottles_of_mate.luac
Also bytecode listing is available by executing following:
$ luac -l bottles_of_mate.lua
main <./bottles.lua:0,0> (13 instructions, 52 bytes at 0x101d530)
0+ params, 4 slots, 0 upvalues, 2 locals, 4 constants, 1 function
1 [1] GETGLOBAL 0 -1 ; require
2 [1] LOADK 1 -2 ; "string"
3 [1] CALL 0 2 2
4 [22] CLOSURE 1 0 ; 0x101d710
5 [22] MOVE 0 0
6 [3] SETGLOBAL 1 -3 ; bottle_take
7 [24] LOADK 1 -4 ; 99
8 [27] GETGLOBAL 2 -3 ; bottle_take
9 [27] MOVE 3 1
10 [27] CALL 2 2 2
11 [27] MOVE 1 2
12 [27] JMP -5 ; to 8
13 [28] RETURN 0 1
function <./bottles.lua:3,22> (46 instructions, 184 bytes at 0x101d710)
1 param, 10 slots, 1 upvalue, 6 locals, 9 constants, 0 functions
1 [5] LOADK 1 -1 ; "%d bottles of mate on the wall."
2 [6] LOADK 2 -2 ; "Take one down, pass it around, "
3 [6] MOVE 3 1
4 [6] CONCAT 2 2 3
5 [7] LOADK 3 -3 ; "Oh noes, "
6 [7] MOVE 4 1
7 [7] CONCAT 3 3 4
8 [8] LOADK 4 -4 ; "Get some from the store, "
9 [8] MOVE 5 1
10 [8] CONCAT 4 4 5
11 [9] LOADK 5 -5 ; 0
12 [11] EQ 1 0 -5 ; - 0
13 [11] JMP 16 ; to 30
14 [12] GETGLOBAL 6 -6 ; print
15 [12] GETUPVAL 7 0 ; string
16 [12] GETTABLE 7 7 -7 ; "format"
17 [12] MOVE 8 1
18 [12] MOVE 9 0
19 [12] CALL 7 3 0
20 [12] CALL 6 0 1
21 [13] SUB 5 0 -8 ; - 1
22 [14] GETGLOBAL 6 -6 ; print
23 [14] GETUPVAL 7 0 ; string
24 [14] GETTABLE 7 7 -7 ; "format"
25 [14] MOVE 8 2
26 [14] MOVE 9 5
27 [14] CALL 7 3 0
28 [14] CALL 6 0 1
29 [14] JMP 15 ; to 45
30 [16] GETGLOBAL 6 -6 ; print
31 [16] GETUPVAL 7 0 ; string
32 [16] GETTABLE 7 7 -7 ; "format"
33 [16] MOVE 8 3
34 [16] MOVE 9 0
35 [16] CALL 7 3 0
36 [16] CALL 6 0 1
37 [17] LOADK 5 -9 ; 99
38 [18] GETGLOBAL 6 -6 ; print
39 [18] GETUPVAL 7 0 ; string
40 [18] GETTABLE 7 7 -7 ; "format"
41 [18] MOVE 8 4
42 [18] MOVE 9 5
43 [18] CALL 7 3 0
44 [18] CALL 6 0 1
45 [21] RETURN 5 2
46 [22] RETURN 0 1
