Display and add varaibles

[basil60]

Hi
I'm a noob and trying to do some basic stuff.

My code looks like this:

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Code: Select all

minetest.register_chatcommand("foo1", {
   privs = {
      interact = true
   },
   func = function(name, param)
      local a = param
   end
})
minetest.register_chatcommand("foo2", {
   privs = {
      interact = true
   },
   func = function(name, param)
      local b = param
   end
})

result = a + b
minetest.chat_send_all(result)

I'm trying to do this:

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Code: Select all

local a = 2     -- Set 'a' to 2
local b = 2     -- Set 'b' to 2
local result = a + b -- Set 'result' to a + b, which is 4
a = a + 10
print("Sum is "..result)

, but instead of doing in the command line, want it to happen in the display.

Where did I go wrong? It doesn't display a result.
Is there a better way to do this?

[qwertymine3]

There are a number of issues with what you have written.

In both of the chat commands you have written local a/b. This makes a/b local to the function, not the file, so they can't be accessed outside their respective function. You need to declare a local a/b outside of any function for it to be file-local.

You have then written the result calculation and chat_send_all call outside of any function. This means that it will be called while the mod is initialising, before either of the two values has been set. IDK why this isn't causing an error, but you need to call it later instead, such as in a third chat command.

Also param is a string, you need to convert it to a number if you want to do arithmetic on it later. This can be done with tonumber().

[basil60]

Thanks
I see you do a lot of work in Minetest. I was trying to work on basic coding examples that use Lua and work within Minestest, to teach some basic programming to kids.

Got any good ideas for simple simple programmes for kids, who'll generally have no idea of coding?

[qwertymine3]

Are you looking for demo ideas (so that complex stuff can be used behind the scenes to make the code look better) or are you looking for code that the kids can write?

It is quite hard to think of examples which don't go too deep into the minetest API and are interactive, but on_palce/on_rightclick maybe a good starting point.

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Code: Select all

minetest.register_craftitem("teaching:conditionals",{
    description = "Change dirt to mese!",
    stack_max = 1,
    inventory_image = "default_mese_block.png",
    on_place = function(_,_,pointed_thing)
        local looking_at = minetest.get_node(pointed_thing.under)
        if looking_at.name == "default:dirt" then
            minetest.set_node(pointed_thing.under,{name = "default:mese"})
        end
    end,
})


[basil60]

Code that kids can write or adapt would be the ideal.

So I've taken a LUA loop - write Hello World 10 times to lay 10 blocks side by side.
That's the kind of progression I had in mind. And I think all they can probably handle!
The API has always been a sticking point (not just in Minetest) for me. It's what separates the "men from the boys".

And I'm barely a lad!!!
Thanks for the example - if you've got others, it'd be great!

[basil60]

qwertymine3
I tried this, in anew mod folder called "teaching"

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Code: Select all

minetest.register_craftitem("teaching:conditionals",{
    description = "Change dirt to water!",
    stack_max = 1,
    inventory_image = "default_water.png",
    on_place = function(_,_,pointed_thing)
        local looking_at = minetest.get_node(pointed_thing.under)
        if looking_at.name == "default:dirt" then
            minetest.set_node(pointed_thing.under,{name = "default:water"})
        end
    end,
})

Am I correct in assuming that if I place a dirt node, it will then change the node to water.
It doesn't seem to change anything.

[Byakuren]

qwertymine3
I tried this, in anew mod folder called "teaching"

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Code: Select all

minetest.register_craftitem("teaching:conditionals",{
    description = "Change dirt to water!",
    stack_max = 1,
    inventory_image = "default_water.png",
    on_place = function(_,_,pointed_thing)
        local looking_at = minetest.get_node(pointed_thing.under)
        if looking_at.name == "default:dirt" then
            minetest.set_node(pointed_thing.under,{name = "default:water"})
        end
    end,
})

Am I correct in assuming that if I place a dirt node, it will then change the node to water.
It doesn't seem to change anything.

It creates a "teaching:conditionals" item that you can use to turn dirt into water by right-clicking the dirt with it.

[basil60]

Thanks
so how can I access that item. Does it put it into one's inventory? Do I need to manually add it to inventory.

[qwertymine3]

You would have to use /giveme teaching:condtionals or the creative inventory menu

Also this may be a good example of these types of loops.

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Code: Select all

  minetest.register_craftitem("teaching:checking_loop",{
         description = "Make a tower of mese!",
         inventory_image = "default_mese_block.png",
         stack_max = 1,
          on_place = function(_,_,pointed_thing)
                  local pos = pointed_thing.under
                  local node = minetest.get_node(pos)
                  while node.name == "default:mese" do
                          pos.y = pos.y + 1
                          node = minetest.get_node(pos)
                  end
                  minetest.set_node(pos,{name = "default:mese"})
          end,
  })
   
  minetest.register_craftitem("teaching:checking_loop_b",{
          description = "Make another tower of mese!",
          inventory_image = "default_mese_block.png",
          stack_max = 1,
          on_place = function(_,_,pointed_thing)
                  local pos = pointed_thing.under
                  repeat
                          pos.y = pos.y + 1
                          node = minetest.get_node(pos)
                  until node.name ~= "default:mese"
                  minetest.set_node(pos,{name = "default:mese"})
          end,
  })     


[basil60]

Cheers

I'll look at it...

[basil60]

So the /giveme worked OK.
I slightly changed the code you gave me:

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Code: Select all

minetest.register_craftitem("teaching:conditionals",{
    description = "Change dirt to water!",
    stack_max = 1,
    inventory_image = "default_water.png",
    on_place = function(_,_,pointed_thing)
        local looking_at = minetest.get_node(pointed_thing.under)
        if looking_at.name == "default:dirt" then
            minetest.set_node(pointed_thing.under,{name = "default:water"})
        end
    end,
})

It now returns an error when I right click on a dirt block:

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Code: Select all

2016-10-06 18:56:06: ERROR[ServerThread]: Map::setNode(): Not allowing to place
CONTENT_IGNORE while trying to replace "default:dirt" at (-25,3,-21) (block (-2,
0,-2))

Hope I'm not just being thick.

[qwertymine3]

So the /giveme worked OK.
I slightly changed the code you gave me:

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Code: Select all

            minetest.set_node(pointed_thing.under,{name = "default:water"})


Hope I'm not just being thick.

The name needs to be default:water_source

[basil60]

Thanks
That's perfect

[qwertymine3]

Here is an example for the basic for loop

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  minetest.register_craftitem("teaching:for_loop",{
          description = "Make a geysir!",
          inventory_image = "default_water.png",
          stack_max = 1,
          on_place = function(_,_,pointed_thing)
                  local pos = pointed_thing.above
                  for i=1,10 do
                          minetest.set_node({x=pos.x,y=pos.y+i,z=pos.z},{name="default:river_water_source"})
                  end     
          end,
  })


[basil60]

Thank you

[basil60]

Qwertymine3 - another really noob question - how do you get rid of the geyser?

[qwertymine3]

Place nodes through the center of the geyser to remove the source nodes