Janko in a Jar

I am no experienced Lua-er. But I got very intrigued after the first “aha” moment happened to me: “aha, so lua is like some super-table language?”. That is of course not all, and many more aha-s did and will follow.

I love minimalism and this is a minimalism at it’s best!

Just some random code to confuse you:

function makeHiSayer(name)
  return function()
    function sayHi(name1)
      print("hi, I am " .. name1)
    end
    local n = name
    sayHi(n)
  end
end
hi = makeHiSayer("janko")
hi()
-- hi, I am janko

from Wikipedia: Although Lua does not have a built-in concept of classes, the language is powerful enough to easily implement them using two language features: first-class functions and tables. By simply placing functions and related data into a table, an object is formed. Inheritance (both single and multiple) can be implemented via the “metatable” mechanism, telling the object to lookup nonexistent methods and fields in parent object(s).

In next example I am not using any of the proposed methods for doing OO in Lua. Basically I am just making stuff up as I go and yet it works.

AmIABulletClass = { x = 10, y = 20, dx = 1, dy = 1,
  update = function (self)
    self.x = self.x + self.dx ;
    self.y = self.y + self.dy
  end }
bul = AmIABulletClass
bul.update(bul)
print(bul["x"])
-- 11
print(bul["y"])
-- 21
bul.update(bul)
print(bul.x)
-- 12
print(bul.y)
-- 22

This entry was posted on Thursday, August 23rd, 2007 at 7:46 pm and is filed under Just programming.