so i know you can do stuff like this in lua to kind of shorten your code so you don't have to make unnecessary if statements
function checkMath(equation)
if equation == 4 then
return true
end
return false
end
workspace.Part.BrickColor = BrickColor.Green() or BrickColor.Red()
but is there a way to do that for a return statement inside a function?
basically, what I'm asking is: is it possible to return amount and items if returnItems is true or only amount if returnItems is false without a if statement?
what I've thought of doing (haven't tested):
countDictItems = function(tab,returnItems)
local amount = 0
local items = {}
for _, ind in pairs(tab) do
amount = amount + 1
end
return amount, items or amount
end
Answered in a separate thread I posted on another website.
function blah(returnitems)
amount = 15
items = {"blah1", "blah2"}
return amount, returnitems and items or nil
end
print(blah(true))
print(blah(false))
output:
>15 table: 0x9e26e0
>15 nil
Related
I'm new to lua, and I'm having trouble with a basic sort-by-bool-condition thing for entries in a table.
`local tblFormReturn = {
{
['Name'] = 'Spike',
['Year'] = '10',
['House'] = 'Holmes',
['Form Returned'] = true
},
{
['Name'] = 'Elvis',
['Year'] = '11',
['House'] = 'Shaw',
['Form Returned'] = true
},
{
['Name'] = 'Michael',
['Year'] = '10',
['House'] = 'Langley',
['Form Returned'] = false
},
{
['Name'] = 'Chang',
['Year'] = '11',
['House'] = 'Holmes',
['Form Returned'] = false
}
}`
Basically, I want to be able to take this table, and for each chunk, check whether the kid is in Holmes house (1) and if they have returned their form (2). My feeling is I need to run a for-loop in pairs based off the lua manual, but I'm confused as to how I can access these values, given each chunk is sort of a sub-table. My attempts have all been based around something like this.
for i,'Form Returned' in tblFormReturned('Form Returned') do
if 'Form Returned' == true then
if 'House' == 'Holmes' then
print ('Number of Holmes forms returned' +1)
end
end
end
I'm not sure how to make this work. Any help greatly appreciated.
A few things of note here.
When you quote something (indicated by using the single quotes), you effectively make it a string.
A for loop loops through a table using ipairs (indexed pairs, such as yours is) or pairs (used on dictionary tables). Dictionary tables are considered those that are have a defined key rather than an index key (e.g. tblPets = {dog = "Fido", cat = "Sassy", duck = "Quackers} - this would allow you to return tblPets.dog (or tblPets["dog"]) to get the value).
Your print statement to add a number does not work. You cannot add a number to a string. Instead, you will need to set a count as a variable and add to it, provided it is a number.
Lastly, you can also combine the if statements into one to make it easier.
formCount = 0 -- This initializes the variable formCount as an interger, starting with 0.
for i,v in ipairs(tblFormReturned) do -- This iterates through the table
if v["Form Returned"] and v.House == "Holmes" then -- Looks to see if the form returned is true and house is Holmes. Note that with boolean values, you do not have to see if it equals true or false. if v["Form Returned"] == true and this format returns the same answer.
formCount = formCount + 1 -- Adds 1 to the formCount
end -- end if statement
end -- end for loop
Hopefully this helps a little with understanding. If you have any questions, don't hesitate to ask for clarification.
Basically what I want to do is convert a table of this format
result={{id="abcd",dmg=1},{id="abcd",dmg=1},{id="abcd",dmg=1}}
to a table of this format:
result={{id="abcd",dmg=1, qty=3}}
so I need to know how many times does {id="abcd",dmg=1} occur in the table. Does anybody know a better way of doing this than just nested for loops?
result={{id="abcd",dmg=1},{id="defg",dmg=2},{id="abcd",dmg=1},{id="abcd",dmg=1}}
local t, old_result = {}, result
result = {}
for _, v in ipairs(old_result) do
local h = v.id..'\0'..v.dmg
v = t[h] or table.insert(result, v) or v
t[h], v.qty = v, (v.qty or 0) + 1
end
-- result: {{id="abcd",dmg=1,qty=3},{id="defg",dmg=2,qty=1}}
So you want to clear duplicate contents, although a better solution is to not let dupe contents in, here you go:
function Originals(parent)
local originals = {}
for i,object in ipairs(parent) do
for ii,orig in ipairs(originals) do
local dupe = true
for key, val in pairs(object) do
if val ~= orig[key] then
dupe = false
break
end
end
if not dupe then
originals[#originals+1] = object
end
end
return originals
end
I tried to make the code self explanatory, but the general idea is that it loops through and puts all the objects with new contents aside, and returns them after.
Warning: Code Untested
Is it faster to check whether a number is equivalent to another, or to look up the number in a table?
I have a program where commands sent from a server are received as numbers. Commands are sent frequently: anywhere from 1/second to 30+/second. Certain commands are ignored while others trigger various events. Would it be better to determine which event to trigger by doing this:
function incoming_integer(n)
if n == 33 then
print('a')
elseif n == 44 then
print('b')
elseif n == 567 then
print('c')
... (the actual list is occasionally pretty long: upwards of ten valid numbers)
end
end
or this:
functions = {
[33] = function() print('a') end,
[44] = function() print('b') end,
[567] = function() print('c') end,
...
}
relevant_commands = {[33]= true, [44]=true, [567]=true ...}
function incoming_integer(n)
if relevant_commands[n] then
functions[n]()
end
end
Is there a point at which one method becomes more efficient?
What if the commands were instead sent as strings?
For your throughput, I would suggest that the overhead for either mechanism is likely to be negligible.
I ran very quick and dirty test of the overhead of the table lookup for both string and numeric keys. See below. Even with a large number of keys and a high hit rate, I struggled to get >1us overhead even on the slowest box I could find.
f = {}
function incoming_integer(n)
local t = f[n]
return t and t()
end
SIZE = 10000
RAN = 20000
REPEAT = 10000000
for i =1,SIZE do
--f[math.random(RAN)] = function() return "z" end
f[tostring(math.random(RAN))] = function() return "z" end
end
tm = os.time()
for i = 1,REPEAT do
--math.random(RAN)
tostring(math.random(RAN))
end
print(os.difftime(os.time(),tm))
tm = os.time()
for i = 1,REPEAT do
--incoming_integer(math.random(RAN))
incoming_integer(tostring(math.random(RAN)))
end
print(os.difftime(os.time(),tm))
If you want to trigger different events with the returned numbers, I would use this way...
function trigger( value )
if ( value == "..." ) then
triggerThis()
elseif ( value == "..." ) then
triggerElse()
-- and so on
end
end
function incoming_integer(n)
if ( n ) then -- check if variable is incoming to prevent errors
trigger( n )
else
alert( "noop, there is nothing here" )
end
end
Maybe you could try keys. Didn't tested it just an example.
http://lua-users.org/wiki/TablesTutorial
table = { [33]="a", [44]="b", [567]="c" }
function onCall( value ) -- if 33
if ( table[value] ) then
return( table[value] ) -- then if exists return a
end
end
onCall( 33 ) -- now it will search in table and get key
EDIT: You could name the triggered functions like the number, so you can directly trigger them. This would save a lot of time!
functions = {[33] = function() print('a') end, etc...}
setmetatable(functions, {__index = function() return function() end end}) -- return empty function if no defined function is found
Usage:
functions[32]() -- ignores
functions[33]() -- does defined function
I have the following string data that I receive as input:
"route1,1234,1,no~,,route2,1234,1,no~,"
It represents two "records" of data... where each record has 4 fields.
I've built code to parse this string into it's individual columns / fields.
But the part that isn't working is when I test to see if I have any duplicates in field 2. Field 2 is the one that currently has "1234" as the value.
Here's the code:
function string:split(delimiter)
local result = { }
local from = 1
local delim_from, delim_to = string.find( self, delimiter, from )
while delim_from do
table.insert( result, string.sub( self, from , delim_from-1 ) )
from = delim_to + 1
delim_from, delim_to = string.find( self, delimiter, from )
end
table.insert( result, string.sub( self, from ) )
return result
end
local check_for_duplicate_entries = function(route_data)
local route
local route_detail = {}
local result =true
local errtxt
local duplicate = false
print("received :" ..route_data)
route = string.gsub(route_data, "~,,", "~")
route = route:sub(1,string.len(route)-2)
print("route :" ..route)
-- break up in to an array
route = string.split(route,"~")
for key, value in pairs(route) do
route_detail[key] = string.split(value,",")
end
local list_of_second_column_only = {}
for key,value in pairs(route_detail) do
local temp = value[2]
print(temp .. " - is the value I'm checking for")
if list_of_second_column_only[temp] == nil then
print("i dont think it exists")
list_of_second_column_only[key] = value[2]
print(list_of_second_column_only[key])
else
--found a duplicate.
return true
end
end
return false
end
print(check_for_duplicate_entries("route1,1234,1,no~,,route2,1234,1,no~,"))
I think where I'm going wrong is the test:
if list_of_second_column_only[temp] == nil then
I think I'm checking for key with the value temp instead of a value with the value that temp contains. But I don't know how to fix the syntax.
Also, I'm wondering if there's a more efficient way to do this.
The number of "records" i receive as input is dynamic / unknown, as is the value of the second column in each record.
Thanks.
EDIT 1
The post I was trying to use as a reference is: Search for an item in a Lua list
In the answer, they show how to test for a record in the table by value, instead of looping through the entire table...
if items["orange"] then
-- do something
end
I was playing around to try and do something similar...
This should be a bit more efficient with only one table creation and less regex matching.
The match does require that you're only interested in dups in the second field.
local function check_for_duplicate_entries(route_data)
assert(type(route_data)=="string")
local field_set = {}
for route in route_data:gmatch"([^~]*)~,?,?" do
local field = route:match",([^,]*)"
if field_set[field] then
return true
else
field_set[field] = true
end
end
return false
end
Try this. It's doing the check on the value of the second field.
I haven't looked at the efficiency.
if list_of_second_column_only[value[2]] == nil then
print("i dont think it exists")
list_of_second_column_only[value[2]] = true
print(list_of_second_column_only[value[2]])
else
--found a duplicate.
return true
end
I'm attempting to compare two tables of equal length with a function, since I don't know of any other way to do so. However, with the following function, it fails to register, and I've no clue why. I'm hoping someone can provide insight to this problem or has a better way of comparing the two tables.
The tables are being populated with the following code:
str = "parameters determined by program (all digits)"
tableone = {}
for word in str:gmatch("%d") do table.insert(tableone,word) end
It's identical for both tables, except, of course, the individual table names. The tables are being populated properly, and display properly when I print them. Here are two tables for the sake of this question:
tableone = {}
tabletwo = {}
for i=1,4 do table.insert(tableone, i) end
for i=1,4 do table.insert(tabletwo, i) end
Obviously, these two tables are going to be equal to each other. The function I wrote to compare the index tables is as follows:
function comparetables(t1, t2)
matchct = 0
for i=1,#t1 do
if t1[i] == t2[i] then
matchct = matchct + 1
end
if matchct == #t1 then
return true
end
end
I tried doing
print(comparetables(tableone,tabletwo))
to see if it'll print "true" but no luck. To me, it seems like it should work without a problem. Yet it doesn't. What am I missing? I've tried searching for something like a table.compare function that someone may have already written, but no such luck in finding one. Thanks for any suggestions!
Additional information:
The reason I'm comparing tables is for a mastermaind-type game. That means the following three rules must apply when comparing tables. The function I created was to just get me started, thinking I could work from there.
When comparing the tables, if the numbers match, Ccount increases by 1.
When comparing tables, if the value exists in a different index position, increment Pcount by 1
For example, with a table of values {1, 3, 3, 4} and a guess of {4, 4, 3, 1}, it would return Pcount of 2 (the one 4 and the 1) and a Ccount of 1 (the three in the third position). I think one of the hardest parts is going to be getting the comparison to recognize that the second 4 in the guess should not increment the Pcount at all.
A slight variant on your code that should work is:
function comparetables(t1, t2)
if #t1 ~= #t2 then return false end
for i=1,#t1 do
if t1[i] ~= t2[i] then return false end
end
return true
end
However I use something more like this: It checks the types of the arguments, their metatables, and a few other cases.
-- This is not clever enough to find matching table keys
-- i.e. this will return false
-- recursive_compare( { [{}]:1 }, { [{}]:1 } )
-- but this is unusual enough for me not to care ;)
-- It can also get stuck in infinite loops if you use it on
-- an evil table like this:
-- t = {}
-- t[1] = t
function recursive_compare(t1,t2)
-- Use usual comparison first.
if t1==t2 then return true end
-- We only support non-default behavior for tables
if (type(t1)~="table") then return false end
-- They better have the same metatables
local mt1 = getmetatable(t1)
local mt2 = getmetatable(t2)
if( not recursive_compare(mt1,mt2) ) then return false end
-- Check each key-value pair
-- We have to do this both ways in case we miss some.
-- TODO: Could probably be smarter and not check those we've
-- already checked though!
for k1,v1 in pairs(t1) do
local v2 = t2[k1]
if( not recursive_compare(v1,v2) ) then return false end
end
for k2,v2 in pairs(t2) do
local v1 = t1[k2]
if( not recursive_compare(v1,v2) ) then return false end
end
return true
end
Here's an example of it in use:
print( recursive_compare( {1,2,3,{1,2,1}}, {1,2,3,{1,2,1}} ) ) -- prints true
print( recursive_compare( {1,2,3,{1,2,1}}, {2,2,3,{1,2,3}} ) ) -- prints false
If you're comparing objects that are more objecty than tabley in an Object oriented sense, then I'd look at implementing the functions in the lua OO way.
Something like this should do the trick:
GameState = {}
GameState.mt = {}
GameState.mt.fns = {}
GameState.mt.__index = GameState.mt.fns
function GameState.new(a,b,c,d)
-- TODO: put argument checks here...
local retval = {}
retval[1] = a
retval[2] = b
retval[3] = c
retval[4] = d
setmetatable(retval, GameState.mt)
return retval
end
function GameState.mt.fns.print( self )
print(" GameState: ", self[1], self[2], self[3], self[4] )
end
function GameState.mt.__tostring( self )
return "GameState: "..self[1].." "..self[2].." "..self[3].." "..self[4]
end
function GameState.mt.__eq(self, other)
-- Check it's actually a GameState, and all its bits match
return getmetatable(other)==GameState.mt and
(self[1] == other[1]) and
(self[2] == other[2]) and
(self[3] == other[3]) and
(self[4] == other[4])
end
Then you'd use it like this:
state1 = GameState.new(1,2,3,4)
state2 = GameState.new(1,2,3,4)
print("State 1 is:")
state1:print()
print("State 2 is:")
print(state2)
print( "state1 == state2 : ", state1 == state2 )
print( "Changing state 2")
state2[1]=2
print( "state1 == state2 : ", state1 == state2 )