calling a function from an argument of another function

[a7s1h1]

Is it possible to call a function from an argument of another function, like this: ?

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function love.load()
   tmr=4
end

-- function "timer" is called from love.update(dt): 
-- The function print('Hi') prints the word "Hi"
function love.update(dt)
     timer(tmr,print('Hi'),dt)
end

-- the timer counts back and when it reaches 0, the function print('Hi') should be performed from an argument "func"
function timer(timer,func,dt)
     if timer>0 then           
          timer=timer-1*dt   
           if timer<=0 then
                return func
           end
     end
     tmr=timer
end

[Starry]

I'm gunna say yes but i'm not certain this is what you're asking. code follows

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function love.load()

	timerx = 4

	function timecount(x,y)
	love.graphics.print(x, 10, 10)
	love.graphics.print(y, 10, 20)
	end

	function testing()
		return "Hi"
	end

	 func = testing()

end

function love.update(dt)
bonzer = dt
end

function love.draw()
timecount(func, bonzer)
end

you can't call dt from draw without problems so I bonzered it to save time and reading, i got stuff to do today >_>

(I would think there is more to this since your return wouldn't always be a string...)
ed: timerx is supposed to be in there too but i forgot to put it back in after fixing dt..my bad

[micha]

In Lua function are first class values. That means that you can call a function and give a function as an argument. See for example the generic sorting function in Lua.

However, "print('Hi')" is not a function. That is why your code would not work. "print" is a function. For your purpose you need some sort of function-factory, that makes a function, that does "print('Hi')".

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function factory(text)
  return function() print(text) end
end

(disclaimer: this is untested, maybe I forgot some brackets or something)

[a7s1h1]

function factory(text)
return function() print(text) end
end

Well, I see, I can set an argument of a function2 as an argument of a function1, which runs the function2. But what if the function does not have any arguments? How can I call it from another function? (The issue is not about printing function, as a matter of fact, it does not even matter, what shoul the function do, the question is how to make it perform)

It won't work, just to describe what I need:

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function1 (function2)
   <perform function2>
end

Or the larger example:

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if a=1 then
   func_1(func_2)
end

function func_1(func)
  <returns func(in that case func=func_2, so the function func_2() should be performed)>
end

function func_2()
   <does not matter what>
end

Of course, neither of these codes will work, but they describe what I'm trying to find.

[micha]

I just realize, my example was overly complicated.

To your question: You can for example define a function, that displays some text, and that does not take any input, as follows:

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fun = function () print('foo') end

Now you have a function, called "fun". If you type

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fun()

It will be executed and display "foo".
And for a simple example of a function, that has a function as argument you could have this:

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function runFunctionIfPositive(a,f)
  if a>0 then
    f()
  end
end

This example is just for illustration. The function checks if a is positive and then runs the function you hand over to it. In this case, it is assumed that f has not input arguments.

[a7s1h1]

Now I understood!
For example, if I create these two functions

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function print(text,x,y)
	love.graphics.setFont(font)
	love.graphics.print(text,x,y)
end

function performfunction(func,ar1,ar2,ar3)
   func(ar1,ar2,ar3)
end

Then calling performfunction(print,'It works!',300,200) will perform function print(text,x,y) and so print the text according to the related arguments.
That is easier than I thought - It appears that just I have to set every element of a function (it's name and each argument) as a separate argument of a function, which calls it.
Thanks a lot for the help!

[Plu]

On a sidenote, I'm not sure it's a good idea to overwrite the "print" function as it's a basic part of Lua and LÖVE. Weird things might happen. Plus you won't be able to print to the console window anymore.

[Robin]

it's name and each argument

Note you're not passing function names, though: you're passing the actual function. You can do:

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performFunction(function(a,b,c) print("Wee", a, b, c) end, 1, 2, 3)
-- prints Wee     1       2       3
-- assuming you didn't bind the name "print" to another function, like you did in your sample

And you don't need to pass each argument to the function calling the other function, if you want it to be the same every time. You can do, for example:

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function performfunction(func,ar1,ar2)
   func(ar1,ar2,ar3, 200)
end