How would I code a function to iterate through one "pages" worth of data? Sample code would be ideal...
So say we image the size of a page is 5 items. If we had a lua table with 18 items it would need to print out:
Page 1: 1 to 5
Page 2: 6 to 10
Page 3: 11 to 15
Page 4: 16 to 18
So assume the data is something like:
local data = {}
data["dog"] = {1,2,3}
data["cat"] = {1,2,3}
data["mouse"] = {1,2,3}
data["pig"] = {1,2,3}
.
.
.
How would one code the function that would do the equivalent of this:
function printPage (myTable, pageSize, pageNum)
-- find items in "myTable"
end
So in fact I'm not even sure if a Lua table used as a dictionary can even do this? There is no specific ordering is there in such a table, so how would you be sure the order would be the same when you come back to print page 2?
The next function allows you to go through a table in an order (albeit an unpredictable one). For example:
data = { dog = "Ralf", cat = "Tiddles", fish = "Joey", tortoise = "Fred" }
function printPage(t, size, start)
local i = 0
local nextKey, nextVal = start
while i < size and nextKey ~= nil do
nextKey, nextVal = next(t, nextKey)
print(nextKey .. " = " .. nextVal)
i = i + 1
end
return nextKey
end
local nextPage = printPage(data, 2) -- Print the first page
printPage(data, 2, nextPage) -- Print the second page
I know this isn't quite in the form you were after, but I'm sure it can be adapted quite easily.
The next function returns the key after the one provided in the table, along with its value. When the end of the table is reached, it returns nil. If you provide nil as the second parameter, it returns the first key and value in the table. It's also documented in Corona, although it appears to be identical.
Related
I need to make a trolleybus number, which won't repeat for game. For example, there is a number "101" and there musn't be more "101". How to do that? I have a code, but I know, he won't work and I won't test it lol
function giveNumber()
local number = math.random(100, 199)
local takedNumbers = {}
local i = 0
local massiv = i+1
script.Parent.pered.SurfaceGui.TextLabel.Text = number
script.Parent.zad.SurfaceGui.TextLabel.Text = number
script.Parent.levo.SurfaceGui.TextLabel.Text = number
script.Parent.pravo.SurfaceGui.TextLabel.Text = number
takedNumbers[massiv] = {number}
end
script.Parent.Script:giveNumber() // what I wrote here? idk...
if number == takedNumbers[massiv] then
giveNumber()
end
i didn't test it, because I think it won't work because this code is something bad
I think this will serve your needs.
In the function generateUniqueNumber, the script loops until it found a number that is not yet in the array. (in other words, that it hasn't given out yet)
Once it found that number, it will insert it into the table to remember that it has given it out, and then it will return the number.
Then on the bottom of the script we just give the numbers to the buses :-)
--[[
Goal: Give all buses a unique number
]]
-- Variables
local takenNumbers = {};
-- This function returns a random number in the range [100, 199] that has not been taken yet
function generateUniqueNumber()
local foundNumber = false;
while not foundNumber do
randomNumber = math.random(100, 199);
if not table.find(takenNumbers, randomNumber) then
table.insert(takenNumbers, randomNumber);
return randomNumber;
end
end
end
-- This function sets the number of the bus
script.Parent.pered.SurfaceGui.TextLabel.Text = tostring(generateUniqueNumber());
script.Parent.zad.SurfaceGui.TextLabel.Text = tostring(generateUniqueNumber());
script.Parent.levo.SurfaceGui.TextLabel.Text = tostring(generateUniqueNumber());
script.Parent.pravo.SurfaceGui.TextLabel.Text = tostring(generateUniqueNumber());
2 things:
I didn't test this code as Roblox is not installed on the pc I'm currently on.
Please try formatting your code nicely next time. It greatly improves the readability! For example, you can use this website:
https://codebeautify.org/lua-beautifier
Simpler
Fill a table with free numbers...
local freenumbers = {}
for i = 1, 99 do freenumbers[i] = i + 100 end
...for every new takennumbers use table.remove() on freenumbers
local takennumbers = {}
if #freenumbers > 0 then
takennumbers[#takennumbers + 1] = table.remove(freenumbers, math.random(1, #freenumbers))
end
I'm currently starting work on a text adventure game in Lua--no addons, just pure Lua for my first project. In essence, here is my problem; I'm trying to find out how I can do a "reverse lookup" of a table using one of its variables. Here's an example of what I've tried to do:
print("What are you trying to take?")
bag = {}
gold = {name="Gold",ap=3}
x = io.read("*l")
if x == "Gold" then
table.insert(bag,gold)
print("You took the " .. gold.name .. ".")
end
Obviously, writing a line like this with every single object in the game would be very... exhausting--especially since I think I'll be able to use this solution for not just taking items but movement from room to room using a reverse lookup with each room's (x,y) coordinates. Anyone have any ideas on how to make a more flexible system that can find a table by the player typing in one of its variables? Thanks in advance!
-blockchainporter
This doesn't directly answer your question as you asked it, but I think it would serve the purpose of what you are trying to do. I create a table called 'loot' which can hold many objects, and the player can place any of these in their 'bag' by typing the name.
bag = {}
loot = {
{name="Gold", qty=3},
{name="Axe", qty=1},
}
print("What are you trying to take?")
x = io.read("*l")
i = 1
while loot[i] do
if (x == loot[i].name) then
table.insert(bag, table.remove(loot,i))
else
i = i + 1
end
end
For bonus points, you could check 'bag' to see if the player has some of that item already and then just update the quantity...
while loot[i] do
if (x == loot[i].name) then
j, found = 1, nil
while bag[j] do
if (x == bag[j].name) then
found = true
bag[j].qty = bag[j].qty + loot[i].qty
table.remove(loot,i)
end
j = j + 1
end
if (not found) then
table.insert(bag, table.remove(loot,i))
end
else
i = i + 1
end
end
Again, this isn't a 'reverse lookup' solution like you asked for... but I think it is closer to what you are trying to do by letting a user choose to loot something.
My disclaimer is that I don't use IO functions in my own lua usage, so I have to assume that your x = io.read("*l") is correct.
PS. If you only ever want objects to have a name and qty, and never any other properties (like condition, enchantment, or whatever) then you could also simplify my solution by using key/val pairs:
bag = {}
loot = { ["Gold"] = 3, ["Axe"] = 1 }
print("What are you trying to take?")
x = io.read("*l")
for name, qty in pairs(loot) do
if x == name then
bag.name = (bag.name or 0) + qty
loot.name = nil
end
end
I have a few notes to start before I specifically address your question. (I just want to do this before I forget, so please bear with me!)
I recommend printing to the terminal using stderr instead of stdout--the Lua function print uses the latter. When I am writing a Lua script, I often create a C-style function called eprintf to print formatted output to stderr. I implement it like this:
local function eprintf(fmt, ...)
io.stderr:write(string.format(fmt, ...))
return
end
Just be aware that, unlike print, this function does not automatically append a newline character to the output string; to do so, remember to put \n at the end of your fmt string.
Next, it may be useful to define a helper function that calls io.read("*l") to get an entire line of input. In writing some example code to help answer your question, I called my function getline--like the C++ function that has similar behavior--and defined it like this:
local function getline()
local read = tostring(io.read("*l"))
return read
end
If I correctly understand what it is you are trying to do, the player will have an inventory--which you have called bag--and he can put items into it by entering item names into stdin. So, for instance, if the player found a treasure chest with gold, a sword, and a potion in it and he wanted to take the gold, he would type Gold into stdin and it would be placed in his inventory.
Based on what you have so far, it looks like you are using Lua tables to create these items: each table has a name index and another called ap; and, if a player's text input matches an item's name, the player picks that up item.
I would recommend creating an Item class, which you could abstract nicely by placing it in its own script and then loading it as needed with require. This is a very basic Item class module I wrote:
----------------
-- Item class --
----------------
local Item = {__name = "Item"}
Item.__metatable = "metatable"
Item.__index = Item
-- __newindex metamethod.
function Item.__newindex(self, k, v)
local err = string.format(
"type `Item` does not have member `%s`",
tostring(k)
)
return error(err, 2)
end
-- Item constructor
function Item.new(name_in, ap_in)
assert((name_in ~= nil) and (ap_in ~= nil))
local self = {
name = name_in,
ap = ap_in
}
return setmetatable(self, Item)
end
return Item
From there, I wrote a main driver to encapsulate some of the behavior you described in your question. (Yes, I know my Lua code looks more like C.)
#!/usr/bin/lua
-------------
-- Modules --
-------------
local Item = assert(require("Item"))
local function eprintf(fmt, ...)
io.stderr:write(string.format(fmt, ...))
return
end
local function printf(fmt, ...)
io.stdout:write(string.format(fmt, ...))
return
end
local function getline()
local read = tostring(io.read("*l"))
return read
end
local function main(argc, argv)
local gold = Item.new("Gold", 3)
printf("gold.name = %s\ngold.ap = %i\n", gold.name, gold.ap)
return 0
end
main(#arg, arg)
Now, as for the reverse search which you described, at this point all you should have to do is check the user's input against an Item's name. Here it is in the main function:
local function main(argc, argv)
local gold = Item.new("Gold", 3)
local bag = {}
eprintf("What are you trying to take? ")
local input = getline()
if (input == gold.name) then
table.insert(bag, gold)
eprintf("You took the %s.\n", gold.name)
else
eprintf("Unrecognized item `%s`.\n", input)
end
return 0
end
I hope this helps!
As you can tell I'm a beginner in lua. I am trying to understand a function I'm stuck at what the following code segment does?
It is used in the following code snippet in the last line:
function classify(txt_dir, img_dir, cls_list)
local acc = 0.0
local total = 0.0
local fea_img = {}
local fea_txt = {}
for fname in io.lines(cls_list) do
local imgpath = img_dir .. '/' .. fname .. '.t7'
local txtpath = txt_dir .. '/' .. fname .. '.t7'
fea_img[#fea_img + 1] = extract_img(imgpath)
fea_txt[#fea_txt + 1] = extract_txt(txtpath)
end
for i = 1,#fea_img do
-- loop over individual images.
for k = 1,fea_img[i]:size(1) do
local best_match = 1
local best_score = -math.huge
for j = 1,#fea_txt do
local cur_score = torch.dot(fea_img[i][{k,{}}], fea_txt[j])
From my understanding, fea_img is a lua table. Is the line fea_img[i][{k,{}}] some sort of slicing for the value for the key 'i' in the table fea_img?
I tried searching for more examples and found this being used here too (last line):
for i = 1,nsamples,batchsize do
-- indices
local lasti = math.min(i+batchsize-1,nsamples)
local m = lasti - i + 1
-- k-means step, on minibatch
local batch = x[{ {i,lasti},{} }]
Any help on this would be really appreciated. Thank you!
In lua you can access a specific index on a table in multiple ways. Like these two examples
local myValue = someTable.theIndex
-- or
local myOtherValue = someTable[2]
So the construct you see here is to access some values from a (nested) table.
Also in lua you can use anything except nil as a index, so even tables are possible.
The line
fea_img[i][{k,{}}]
Can be extended to this:
local index1 = i -- i in this case is your loop variable
local index2 = { k , { } } -- This creates a table with 2 values, the first one will be the vaule of the var k, the second one is an empty table
local value1 = fea_img[index1] -- This will get you a table
local value2 = value1[index2] -- This will get the same as: fea_img[i][{k,{}}]
Correction and Addition:
As Nicol Bolas already said in the comments: The index must be an exact match. Which means it literally has to be the same table, which is not the case for the presented code from you. Either you dropped code you thought is unnecessary or fea_img has some some kind of metatable on it.
In the case of
local k = 2
local table1 = {k, { } }
local table2 = {k, { } }
table2 and table1 do have the exact same content. But they are not the same table. Which will lead to nil always being retrieved if one is used to store data in a table and the other is used to get it back.
Syntactically, t[k] is indexing a table with a key. Normally, if there is a record in the table with the key k, its value is returned. Nothing more, nothing less.
If fea_img[i] was a normal table, {k,{}} would always return nil, since table indices are resolved based on their identity ({k,{}} is always a new table). Based on your code, I have to conclude that the elements of fea_img (i.e. what extract_img returns) are not normal tables.
In Lua, you can override the indexing operation using a metatable. If you index a value that has a metatable with __index, it will be used if there is no matching record in the table:
local t = {}
setmetatable(t, {
__index = function(t, k)
return k
end
})
print(t[{}])
This table has a metatable associated with it, which is used in the indexing operation. In this case __index returns the key, but whatever library you are using might provide more complex behaviour.
This is specific to the library you are using, not something related to the Lua syntax.
I have done lots of research on invetory system for point and click game in Lua and corona.
I have come across this example,I am doing something similar to this,but I need a dynamic inventory system.
I mean if I have 4 slots,and all them are full the fifth object go to next slot,so there will be an arrow to the right so I can click on ;and go to the next page.
And imagine there are 5 items,and I have 4 slots,the fifth slot would be on the next page.
I use the third item,and third slot would then be empty,so I want the fourth and fifth item automatically move back to third and fourth slot.
I have hard time figuring this out.
Thanks for advance.
local myInventoryBag={}
local maxItems = 10 -- change this to how many you want
myInventoryBag[5]=3 -- Hammer for instance
myInventoryBag[4]=7 -- A metal Pipe for instance
local function getImageForItem(thisItem)
local itemNumber = tonumber(thisItem)
local theImage=""
if itemNumber==3 then
theImage="hammer.png"
elseif itemNumber == 7 then
theImage="metalpipe.png"
elseif ... -- for other options
...
else
return nil
end
local image = display.newImage(theImage)
return image
end
local function displayItems()
local i
for i=1,#myInventoryBag do
local x = 0 -- calculate based on the i
local y = 0 -- calculate based on the i
local image = getImageForItem(myInventoryBag[i])
if image==nil then return end
image.setReferencePoint(display.TopLeftReferencePoint)
image.x = x
image.y = y
end
end
local itemImages =
{
[0] = display.newImage('MISSING_ITEM_IMAGE.PNG'),
[3] = display.newImage('hammer.png'),
[7] = display.newImage('metalpipe.png'),
}
function getImageForItem(itemId)
return itemImages[itemId] or itemImages[0]
end
local myInventoryBag={}
local maxItems = 10 -- change this to how many you want
local visibleItems = 4 -- show this many items at a time (with arrows to scroll to others)
-- show inventory items at index [first,last]
local function displayInventoryItems(first,last)
local x = 0 -- first item goes here
local y = 0 -- top of inventory row
for i=first,last do
image = getImageForItem(myInventoryBag[i])
image.x = x
image.y = y
x = x + image.width
end
end
-- show inventory items on a given "page"
local function displayInventoryPage(page)
page = page or 1 -- default to showing the first page
if page > maxItems then
-- error! handle me!
end
local first = (page - 1) * visibleItems + 1
local last = first + visibleItems - 1
displayInventoryItems(first, last)
end
myInventoryBag[5] = 3 -- Hammer for instance
myInventoryBag[4] = 7 -- A metal Pipe for instance
displayInventoryPage(1)
displayInventoryPage(2)
Basically what you would do is loop through all the inventory slots and check if the slot is empty. If it's empty, place the item in that slot and stop the loop. If it's not, go to the next one.
If you want to remove an item from the inventory, you can simply call table.delete(myInventoryBag, slotToEmpty).
For pages, you'd simply have a page variable. When drawing the inventory slots, just loop from slots (page-1) * 4 + 1 to page * 4.
(Edit: I'd highly recommend using proper indentation, as it will make the code much much more readable.)
What I'm currently trying to do is make a table of email addresses (as keys) that hold person_records (as values). Where the person_record holds 6 or so things in it. The problem I'm getting is that when I try to assign the email address as a key to a table it complains and says table index is nil... This is what I have so far:
random_record = split(line, ",")
person_record = {first_name = random_record[1], last_name = random_record[2], email_address = random_record[3], street_address = random_record[4], city = random_record[5], state = random_record[6]}
email_table[person_record.email_address] = person_record
I wrote my own split function that basically takes a line of input and pulls out the 6 comma seperated values and stores them in a table (random_record)
I get an error when I try to say email_table[person_record.email_address] = person_record.
But when I print out person_record.email_address it's NOT nil, it prints out the string I stored in it.. I'm so confused.
function split(str, pat)
local t = {} -- NOTE: use {n = 0} in Lua-5.0
local fpat = "(.-)" .. pat
local last_end = 1
local s, e, cap = str:find(fpat, 1)
while s do
if s ~= 1 or cap ~= "" then
table.insert(t,cap)
end
last_end = e+1
s, e, cap = str:find(fpat, last_end)
end
if last_end <= #str then
cap = str:sub(last_end)
table.insert(t, cap)
end
return t
end
The following code is copy and pasted from your example and runs just fine:
email_table = {}
random_record = {"first", "second", "third"}
person_record = {first_name = random_record[1], last_name = random_record[1], email_address = random_record[1]}
email_table[person_record.email_address] = person_record
So your problem is in your split function.
BTW, Lua doesn't have "hashtables". It simply has "tables" which store key/value pairs. Whether these happen to use hashes or not is an implementation detail.
It looks like you iterating over some lines that have comma-separated data.
Looking at your split function, it stops as soon as there's no more separator (,) symbols in particular line to find. So feeding it anything with less than 3 ,-separated fields (for very common example: an empty line at end of file) will produce a table that doesn't go up to [3]. Addressing any empty table value will return you a nil, so person_record.email_address will be set to nil as well on the 2nd line of your code. Then, when you attempt to use this nil stored in person_record.email_address as an index to email_table in 3rd line, you will get the exact error you've mentioned.