Demo of a class num representing a number which implements basic math operations. This is a mini object oriented demo with Lua.
num.lua:
num = {}
num_mt = {
__newindex = function(t, k, v) error('not permitted to create field \'' .. k .. '\'') end,
__index = num,
__add = function(a, b) return setmetatable({ v = a.v + b.v }, num_mt) end,
__sub = function(a, b) return setmetatable({ v = a.v - b.v }, num_mt) end,
__mul = function(a, b) return setmetatable({ v = a.v * b.v }, num_mt) end,
__div = function(a, b) return setmetatable({ v = a.v / b.v }, num_mt) end,
__mod = function(a, b) return setmetatable({ v = a.v % b.v }, num_mt) end,
__pow = function(a, b)
if type(b) == type(num) then
return setmetatable({ v = a.v ^ b.v }, num_mt)
else
return setmetatable({ v = a.v ^ tonumber(b) }, num_mt)
end
end,
__eq = function(a, b) return a.v == b.v end,
__lt = function(a, b) return a.v < b.v end,
__le = function(a, b) return a.v <= b.v end,
__gt = function(a, b) return a.v > b.v end,
__ge = function(a, b) return a.v >= b.v end,
__tostring = function(a) return tostring(a.v) end,
}
function num:new(val)
return setmetatable({ v = val }, num_mt)
end
function num:val()
return self.v
end
a = num:new(10)
b = num:new(20)
c = num:new(3)
print(a:val(), b:val(), (a+b):val(), (a*b):val(), (a ^ 2):val(), (a ^ c):val())