That facepalm moment when ...

[togFox]

... I spent 2 hours trying to nut out my failed vector math only to discover I didn't convert to radians.

You?

[darkfrei]

Code: Select all

function update_vector (vector, reset_vector)
  if reset_vector then 
    vector = {0,0} 
  end
end

local vector = {1,1}
update_vector (vector, true)
print (vector[1]..' '..vector[2]) -- 1 1

[milon]

Haha! Been there, done that - both of those, actually!

Here's most recent facepalm:

Code: Select all

    for x = 1, width do
        for y = 1, height do
            heightmap[x][y] = 1 - math.abs(heightmap[x][y] * 2 - 1)
            watermap[x][y] = math.abs(heightmap[x][y] * 2 - 1)
        end
    end

[darkfrei]

Haha! Been there, done that - both of those, actually!

Here's most recent facepalm:

Code: Select all

    for x = 1, width do
        for y = 1, height do
            heightmap[x][y] = 1 - math.abs(heightmap[x][y] * 2 - 1)
            watermap[x][y] = math.abs(heightmap[x][y] * 2 - 1)
        end
    end

What was expected? Something like this?

Code: Select all

for x = 1, width do
	for y = 1, height do
		local h = math.abs(heightmap[x][y] * 2 - 1)
		heightmap[x][y] = 1 - h
		watermap[x][y] = h
	end
end

[milon]

Nah, it was copypasta. The line should have read:
watermap[x][y] = math.abs(watermap[x][y] * 2 - 1)

But I see where you're coming from. I didn't exactly give any context.

[ZuccaroMateo]

Code: Select all

function update_vector (vector, reset_vector)
  if reset_vector then 
    vector = {0,0} 
  end
end

local vector = {1,1}
update_vector (vector, true)
print (vector[1]..' '..vector[2]) -- 1 1

hey, why is it printing 1 1?

[MrFariator]

hey, why is it printing 1 1?

Tables are passed by reference in lua. As such, if you pass in a table and do some modifications on it, then those changes will persist even after the function finishes. However, in the posted code, when the reset_vector is any non-falsey value, the table the variable "vector" points to doesn't get modified. Instead, the "vector" variable is reassigned to look at a new table. This leaves the original table untouched, so the code will print 1,1 after the function is over.

The correct code for the function would be like

Code: Select all

function update_vector (vector, reset_vector)
  if reset_vector then 
    vector[1] = 0
    vector[2] = 0
  end
end

[darkfrei]

Code: Select all

print (vector[1]..' '..vector[2]) -- 1 1

hey, why is it printing 1 1?

It's "facepalm" topic, when you unterstand that your mind expectations do not match the Lua reality.

I've made this mistake because I can

[Xii]

hey, why is it printing 1 1?

Took me a moment to get it.
Within the function, the local parameter named "vector" is assigned to point to something else.
It's illustrated by renaming this variable:

Code: Select all

function update_vector (localparameter)
    localparameter = {0,0} 
end
local vector = {1,1}
update_vector (vector)
print (vector[1]..' '..vector[2]) -- 1 1

It doesn't actually touch the vector at all.
The confusion arises from both the external and parameter variables being named "vector".

[darkfrei]

hey, why is it printing 1 1?

Took me a moment to get it.
Within the function, the local parameter named "vector" is assigned to point to something else.
It's illustrated by renaming this variable:

Code: Select all

function update_vector (localparameter)
    localparameter = {0,0} 
end
local vector = {1,1}
update_vector (vector)
print (vector[1]..' '..vector[2]) -- 1 1

It doesn't actually touch the vector at all.
The confusion arises from both the external and parameter variables being named "vector".

But!

Code: Select all

function update_vector (localparameter)
    localparameter[1] = 0
    localparameter[2] = 0
end
local vector = {1,1}
update_vector (vector)
print (vector[1]..' '..vector[2]) -- 0 0