I want to print the table, more complex. like this:
I don't know how to check each value in the table that equals and connects string like this (value1, value2, value3, and value4) Before it ends, it must end with and
Table:
table = {
{amount = 1, items = "item1"},
{amount = 1, items = "item2"},
{amount = 1, items = "item3"},
{amount = 2, items = "item4"},
{amount = 3, items = "item5"},
}
P.S I need to sort them too.
table.sort(table, function(a,b) return a.amount < b.amount end)
but I am still stuck with connect string that I mentioned above.
I want it to output like this:
3x item5
2x item4
1x item1, item2, and item3
Thanks for the answers, I newbie to Lua, and English is not my native language. Sorry for the incorrect grammar and words.
the solution is something like this, only without the output of and between item2, and item3 :
local t = {
{amount = 1, items = "item1"},
{amount = 1, items = "item2"},
{amount = 1, items = "item3"},
{amount = 2, items = "item4"},
{amount = 3, items = "item5"},
}
local res = {}
for k,v in pairs(t) do
res[v.amount] = res[v.amount] and (res[v.amount] .. ', ' .. v.items) or v.items -- use ternary operator
end
for k,v in pairs(res) do
v = v:gsub("(.*), (.-)","%1 and %2")
print(k,v)
end
Related
How do I get the full path to the required value in the table? I want to track changes in another table through a proxy table.
I understand that I need to use metatables and __index in it. But I haven't been able to come up with a tracker yet.
Sample table structure:
Objects = {
Panel = { layer = 1, x = 600, y = 328, w = 331, h = 491;
objects = {
label = { layer = 1, x = 0, y = 0, text = 'header' };
Window = { layer = 2, x = 400, y = 100, w = 100, h = 100;
objects = {
label = { layer = 1, x = 0, y = 0, text = 'lorem ipsum dorem' };
};
};
};
};
};
Path: Objects.Panel.objects.Window.objects.label.text
I tried to create a metatable for each of the tables and collect the result of each call to __index into a table in order to roughly understand which key and value were retrieved or changed in order to synchronize these values with other tables.
This will prove itself to be horrendously slow and memory inefficient. Anyway, you were right on the track: proxy and handle __index and __newindex metamethods to your liking. This being said you also need to track the state of the proxy somehow.
You can try to hide it with some closures and upvalues but the easy way is to store the information directly in the proxy tables:
function make_tracker (o, name)
local mt = {}
mt.__index = function (proxy, key)
local path = {unpack(rawget(proxy, "__path"))} -- Stupid shallow copy
local object = rawget(proxy, "__to")
table.insert(path, key)
if type(object[key]) == "table" then
return setmetatable({__to = object[key], __path = path}, mt)
else
return table.concat(path, ".") .. " = " .. tostring(object[key])
end
end
return setmetatable({__to = o, __path = {name}}, mt)
end
__to fields indicates what proxy should point to and __path is there to cover fields we have trespassed so far. It does a shallow copy, so that one can use subproxies with local variables. name parameter is there to initialize the name of the first table, as you just simply can't know that. You use it like this:
local tObjects = make_tracker(Objects, "Objects")
local subproxy = tObjects.Panel.objects.Window
print(subproxy.objects.label.text)
print(tObjects.Panel.objects.label.text)
print(subproxy.x)
-- prints:
-- Objects.Panel.objects.Window.objects.label.text = lorem ipsum dorem
-- Objects.Panel.objects.label.text = header
-- Objects.Panel.objects.Window.x = 400
Of course, I doubt that appending the path to the original value is what you want. Modify insides of else block:
return table.concat(path, ".") .. " = " .. tostring(object[key])
according to your needs, e.g:
register_tracked_path(table.concat(path, "."))
return object[key]
If you want to handle modification of values you need to extend the metatable with similar __newindex.
I've made a table like this
TableAlpha = {
Alpha = 3648,
Beta = 6593,
Charlie = 2358,
Delta = 6483,
Echo = 4736
}
Im wondering how can i pull out 3 keys with lowest values inside the table?
local TableAlpha = {
Alpha = 3648,
Beta = 6593,
Charlie = 2358,
Delta = 6483,
Echo = 4736
}
--- Returns the keys of tab sorted numerically by their values
local function ascending(tab)
local list = {}
for key, integer in pairs(tab) do
table.insert(list, {integer, key})
end
table.sort(list, function(left, right) return left[1] < right[1] end)
for i, tuple in ipairs(list) do
list[i] = tuple[2]
end
return list
end
local unpack = unpack or table.unpack or error("Could not find an unpack function!")
print(unpack(ascending(TableAlpha), 1, 3))
This may be easier than I'm making it on myself. I am relatively new to Lua, but experienced in other languages.
I have a table that looks like this:
local state = {}
state[1] = {
show = true,
changed = true,
progressType = "static",
value = 0,
total = 9,
name = "nine",
}
state[2] = {
show = true,
changed = true,
progressType = "static",
value = 0,
total = 7,
name = "seven",
}
state[3] = {
show = true,
changed = true,
progressType = "static",
value = 0,
total = 8,
name = "eight",
}
state[4] = {
show = true,
changed = true,
progressType = "static",
value = 0,
total = 6,
name = "six",
}
What I need to do is sort each table[] entry based on the value of table.value5. I can't find any functions in the docs that expressely say they do more than just a basic table.sort so I find myself a bit stuck. Do I need to manually sort by iterating through and creating a new table with the sorted data?
I can't find any functions in the docs that expressely say they do more than just a basic table.sort so I find myself a bit stuck.
I might be misunderstanding your issue, but table.sort is exactly what you need in this case:
local state = {}
state[1] = {
total = 9,
name = "nine",
}
state[2] = {
total = 7,
name = "seven",
}
state[3] = {
total = 8,
name = "eight",
}
state[4] = {
total = 6,
name = "six",
}
-- Use table.sort with a custom anonymous function
-- to specify how to compare the nested tables.
table.sort(state, function (a, b)
return a.total < b.total
end)
for i=1, #state do
print(i, state[i].name)
end
With table.sort you can provide an optional custom function, which can be as easy or complicated as you want it to be. In this case (as per your question) it is enough to simply compare the total values of your table.
I'm trying to figure out how to dynamically build a series of sub-tables inside a lua table. For example
function BuildsubTable()
local oTable = {}
local name = {"P1","P2"}
for i = 1, 2 do
oTable[i] = {name = name[i], "x" = i + 2, "y" = i + 1}
end
return oTable
end
expected output:
oTable = {
{name = "P1", "x"=3, "y"=2},
{name = "P2", "x"=4, "y"=3}
}
Which obviously doesn't work, but you get the idea of what I'm trying to do. This is a rather simple task but in LUA 5.3 this is proving to be difficult. I cannot find a good example of building a table in this manner. Any solutions or other ideas would be appreciated. In Python I would use a class or a simple dictionary.
Your problem is that you quote the string indices. The generic syntax for declaring a table key inside the table constructor is [<key>] = <value>, for example, [20] = 20 or ["x"] = i + 2.
A shorthand for ["<key>"] = <value>, that is, for string indices that are valid variable names, you can write <key> = <value>, for example x = i + 2.
In your code you use a mix of both and write { ..., "x" = i + 2, ... }. A quick google search shows me that in Python, which you mention, you quote string keys in dictionaries, so you probably mixed that up with Lua?
EDIT: I noticed this a bit late, but you can also use ipairs to iterate the first table and table.insert to insert values:
function BuildsubTable()
local oTable = {}
local name = {"P1","P2"}
for i,name in ipairs(name) do
table.insert(oTable, {name = name, "x" = i + 2, "y" = i + 1})
end
return oTable
end
Use
oTable[i] = {name = name[i], x = i + 2, y = i + 1}
DarkWiiPlayers & lhf's answers are the proper way.
But here is how you can fix your current code if you intend to use a string as a key
function BuildsubTable()
local oTable = {}
local name = {"P1","P2"}
for i = 1, 2 do
oTable[i] = {name = name[i], ["x"] = i + 2, ["y"] = i + 1}
end
return oTable
end
Output
{
[1] = { ['name'] = 'P1', ['x'] = 3, ['y'] = 2},
[2] = { ['name'] = 'P2', ['x'] = 4, ['y'] = 3}
}
I have a table called "inventory", initialized like so:
inventory = {}
inventory[1] = { qty = 0 }
I want to add more data to this table, at the index 1, eg:
val = { id = "example" }
inventory[1] = inventory[1], val
Is there a way I can do this while preserving the data that is already in this table at this index?
The final result should be something like:
inventory[1] = { qty = 0, id = "example" }
But if I try to print the id after trying this code I get:
print(inventory[1].id) == Nil
inventory[1].id = "example"
or
inventory[1]["id"] = "example"
or
this other SO answer with first_table being inventory[1] and second_table being val.
FWIW, you'd need 2 variables on the left side of the expression for inventory[1] = inventory[1], val to work: a, b = x, y.
You need to take the first key in the table and use it:
local inventory = {}
inventory[1] = { qty = 0 }
local val = { id = "example" }
--
local KeyName = next(val)
inventory[1][KeyName] = val[KeyName]
print(inventory[1][KeyName])
-- or
print(inventory[1].id)