Ceres' Lua Problems

[Ceres]

Now the stderr.txt complains that altar_goto[0].x is an invalid WML array index
Is it impossible to set indexes like that?

[Anonymissimus]

Now the stderr.txt complains that altar_goto[0].x is an invalid WML array index

Should happen if the wml array value altar_goto[0].x doesn't exist when evaluating the variable (but not when setting it).

EDIT
Here's the lua part improved with the error above supposed to disappear (untested):

Code: Select all

		local helper = wesnoth.require "lua/helper.lua"
		local altar_victims = helper.get_variable_array "altar_victims"
		wesnoth.set_variable("altar_goto")
		for i, v in ipairs(altar_victims) do
			local altar_path = wesnoth.find_path (v.x, v.y, 22, 14, {ignore_units = false, viewing_side = 0})
			wesnoth.set_variable ("altar_goto[" .. i-1 .. "].x", altar_path[i][1])
			wesnoth.set_variable ("altar_goto[" .. i-1 .. "].y", altar_path[i][2])
			wesnoth.set_variable ("altar_goto[" .. i-1 .. "].id", v.id)
		end

[Ceres]

It actually worked (the evaluated coordinates were the hex the unit was standing on, but I figured it out myself)! Thank you all so much!
Lua doesn't seem to like me, so I'd better stay wth WML for now.
Edit+repost: Sigh. Sometimes it's working as I want it, but often the code spawns this:
20110718 17:32:10 error scripting/lua: [string "..."]:7: attempt to index field '?' (a nil value)
stack traceback:
[string "..."]:7: in function 'bytecode'
...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:247: in function 'cmd'
...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:290: in
function 'handle_event_commands'
...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:305: in
function 'if_while_handler'
...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:311: in function 'cmd'
...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:290: in
function 'handle_event_commands'
...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:305: in
function 'if_while_handler'
...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:315: in function 'cmd'
...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:290: in
function <...(x86)/Battle for Wesnoth 1.9.7/data/lua/wml-tags.lua:254>
20110718 17:32:10 error engine: Formula in WML string cannot be
evaluated due to Could not parse expression --> "9 13 "

Code:

Code: Select all

	[set_variable]
			name=range_counter
			value=1
		[/set_variable]
		[while]
			[variable]
				name=range_counter
				less_than_equal_to=8
			[/variable]
			[do]
				[store_unit]
					[filter]
						[not]
							role=altar_moved
							[or]
								x,y=22,14
							[/or]
						[/not]
						[filter_location]
							x,y=22,14
							radius=$range_counter
						[/filter_location]
					[/filter]
					variable=altar_victims
				[/store_unit]
				[if]
					[variable]
						name=altar_victims.length
						greater_than=0
					[/variable]
					[then]
						[lua]
							code= <<
								local helper = wesnoth.require "lua/helper.lua"
								local altar_victims = helper.get_variable_array "altar_victims"
								wesnoth.set_variable("altar_goto")
								for i, v in ipairs(altar_victims) do
									local altar_path = wesnoth.find_path (v.x, v.y, 22, 14, {ignore_units = false, viewing_side = 0})
									wesnoth.set_variable ("altar_goto[" .. i-1 .. "].x", altar_path[i+1][1])
									wesnoth.set_variable ("altar_goto[" .. i-1 .. "].y", altar_path[i+1][2])
									wesnoth.set_variable ("altar_goto[" .. i-1 .. "].id", v.id)
								end
							>>
						[/lua]
						{FOREACH altar_goto i}
							[if]
								[not]
									[have_unit]
										x,y=$altar_goto[$i].x,$altar_goto[$i].y
									[/have_unit]
								[/not]
								[then]
									[move_unit]
										id=$altar_goto[$i].id
										to_x=$altar_goto[$i].x
										to_y=$altar_goto[$i].y
									[/move_unit]
								[/then]
							[/if]
							[modify_unit]
								[filter]
									id=$altar_goto[$i].id
								[/filter]
								role=altar_moved
							[/modify_unit]
						{NEXT i}
					[/then]
				[/if]
				[set_variable]
					name=range_counter
					add=1
				[/set_variable]
				[clear_variable]
					name=altar_victims
				[/clear_variable]
			[/do]
		[/while]

[Elvish_Hunter]

error scripting/lua: [string "..."]:7: attempt to index field '?' (a nil value)

And at line 7 we have...

Code: Select all

wesnoth.set_variable ("altar_goto[" .. i-1 .. "].x", altar_path[i+1][1])

Here, the only thing that can be nil is altar_path[i+1][1]. I'm not sure, as it's always hard to guess what goes wrong, but what about trying to replace it with altar_path[i][1] ?
Also, a suggestion: when there are such problems, use print() to check the values of suspicious variables. It can be really helpful.

[Ceres]

That's what it was before, but it seemed to evaluate the wrong hex, namely the one the unit is standing on. My code was working sometimes, but not always.

[Elvish_Hunter]

So, I tested your code, by putting it in a [set_menu_item] to make my life simpler. There were some things to notice:
- first, why use get_variable_array when you can simply use wesnoth.get_units?
- to move the units of one hex, you needed to use the second step in the iterator returned by find_path. Using index+1 had the consequence of attempting to read on-existent steps.
- to pass the radius parameter, I used the (...) table, that collects everything that is supplied in the [args] tag.
- I also used string.format instead of multiple concatenations.
See here:

Spoiler:

Code: Select all

		[set_menu_item]
			description=Altar move
			id=altar
			[command]
				[lua]
					code=<<
						local t = (...)
						helper = wesnoth.require "lua/helper.lua"
						local altar_victims = wesnoth.get_units( { { "not", { role = "altar_moved" } }, { "filter_location", { x=22, y=14, radius=t.radius } } } )
						-- print ( "Units: " .. #altar_victims )
						wesnoth.set_variable( "altar_goto" ) -- making it nil erases it
						for index, victim in ipairs ( altar_victims ) do
							local altar_path = wesnoth.find_path( victim.x, victim.y, 20, 14, { ignore_units = false, viewing_side = 0 } )
							-- print ( index, victim.id, #altar_path )
							if #altar_path >= 2 then -- if a unit is already on the hex we avoid an error
								--for i, loc in ipairs( altar_path ) do print ( "Altar path " .. i .. ": " .. loc[1] .. " " .. loc[2] ) end
								-- [1] is the starting loc, [2] the next step
								wesnoth.set_variable ( string.format( "altar_goto[%d].x", index - 1 ), altar_path[2][1] )
								wesnoth.set_variable ( string.format( "altar_goto[%d].y", index - 1 ), altar_path[2][2] )
								wesnoth.set_variable ( string.format( "altar_goto[%d].id", index - 1 ), victim.id )
								--print ( "Victim: " .. altar_path[index+1][1], altar_path[index+1][2], victim.id )
							end
						end
					>>
					[args]
						radius = $range_counter
					[/args]
				[/lua]
				[set_variable]
					name=range_counter
					add=1
				[/set_variable]
			[/command]
		[/set_menu_item]

I left (but commented) all the print() lines, so you can see how I tracked down the bug. I also change the variable names to be long and more understandable. If there is anything unclear, just ask.

[Ceres]

At first I thought that something in your code was broken, but then I noticed you changed the hex the units are pulled towards from 22;14 to 20;14, whyever.
Apart from that, you kindly healed my ailing code (forever now, hopefully)
One thing I want to know since months: what exactly is ipairs() doing? I looked for tutorials and references, but always lost the thread somewhere...

[Elvish_Hunter]

I needed to change the location only because of the map that I used, that was 20 x 20.
About ipairs, it iterates through a table, and for every item it returns a numeric value (index) and the item itself. More informations are available at lua-users.org .

[Ceres]

Yet another question: What's the difference between tables, WML tables and proxy units?

[Luther]

A WML table is a table that can be translated directly to WML. They're very complicated to type without using set_wml_tag_metatable. The following Lua and WML are equivalent:

Lua:

Code: Select all

H = wesnoth.require('lua/helper.lua')
T = H.set_wml_tag_metatable{}

{
  --x, y, and radius are WML attributes
  x = 84,
  y = 42,
  radius = 1,

  --This is a [filter_radius] tag with its own WML table
  T.filter_radius{
    terrain = 'K*,C*'
  }
}

WML:

Code: Select all

x=84
y=42
radius=1
[filter_radius]
  terrain=K*,C*
[/filter_radius]

A proxy unit is like a table, but it gives you direct access to a unit in the engine. A full description is at LuaWML:Units. You cannot write one from scratch. It must be returned by one of the functions on that wiki page.

Let us know if you need any clarification.

[Anonymissimus]

A wml table is a normal lua table which additionally fullfills several syntax rules. I listed them somewhere in my lua thread (at the time I wrote the dbms function from the WLP).

A proxy unit is like a table

When dumped by calling the __cfg field, yes. Other than that it's a read-only lua userdata which is owned by the C++ code which allows you several ways of accessing and modifying.

[Elvish_Hunter]

Just for completeness, the code posted by Luther will be the following, if you don't use set_wml_tag_metatable:

Code: Select all

{
  x = 84,
  y = 42,
  radius = 1,
  { "filter_radius", { terrain = 'K*,C*' } }
}

If you do not want to use the metatable, the rule is to create a table where the first element is the tag name ( "filter_radius" ), and the second element is another table containing all the keys and values ( { terrain = 'K*,C*' } ).

[Ceres]

Thank you. All right then, I messed around with this code for hours now trying to create a [find_path] tag. Yet Wesnoth complains about
"attempt to index field '?' (a number value)".
Could someone kindly point out where this error comes from? I tried to franken-code as much as possible from working snippets, but apparently I failed somewhere.

Code: Select all

function wml_actions.find_path(cfg)
	local variable = cfg.variable or "path"
	local unit = wesnoth.get_units(helper.get_child(cfg, "filter"))[1]
	local to_x = cfg.to_x
	local to_y = cfg.to_y
	local findpath = wesnoth.find_path ( unit.x, unit.y, to_x, to_y, { ignore_units = false})
	for i, v in ipairs(findpath) do
		wesnoth.set_variable(string.format(variable .. "[%d].x", i-1), v[i][1])
		wesnoth.set_variable(string.format(variable .. "[%d].y", i-1), v[i][2])
	end
end

[Anonymissimus]

untested:

Code: Select all

function wml_actions.find_path(cfg)
	local variable = cfg.variable or "path"
	local unit = wesnoth.get_units(helper.get_child(cfg, "filter"))[1]
	local to_x = cfg.to_x
	local to_y = cfg.to_y
	local findpath = wesnoth.find_path ( unit.x, unit.y, to_x, to_y, { ignore_units = false})
	for i, v in ipairs(findpath) do
		wesnoth.set_variable(string.format(variable .. "[%u].x", i-1), v[1])
		wesnoth.set_variable(string.format(variable .. "[%u].y", i-1), v[2])
	end
end

The structure of the arrays returned by find_path and get_locations is like { {a, b}, {c, d}, ... } so v in this loop will be {a, b} and then {b, c}, ...

[Elvish_Hunter]

I messed around with this code for hours now trying to create a [find_path] tag.

In case that you are interested, some months ago I created a [find_path] tag, that is available in the Wesnoth Lua Pack.