I am trying to have one variable that has a number value as well as a string value.
I am coding in Lua and I don't know how to do this. Is it possible?
Tables. They are like a filing cabinet where you can store as many values as you want and retrieve them given some kind of "key". In Lua, the key can be any type, but the most common key is going to be a numerical index or a string.
Given:
local age = 30 -- your number values
local name = 'Fred' -- your string value
There's a tons of different ways we can structure that in Lua:
local person = { age = 30, name = 'Fred' )
print(person.age, person.name)
local person = { 'Fred', 30 }
print(person[1], person[2])
print(unpack(person))
local person = { Fred = 30 }
print(person.Fred)
local person = { [30] = 'Fred' }
print(person[30])
So on and so forth.
So if i use..
coal = { name = "Coal", value = 80 }
I can then do this?
userInput = read()
if userInput == coal.name then
fuelUse = coal.value
end
Related
I am using the Terraform provider mrparkers/keycloak to attempt to assign Keycloak groups a list of users.
The snippet below creates realms, groups, and users correctly, but I am stumped on the final line for calling a list of users which should belong to the group being looped through.
Anything to point me in the right direction would be hugely appreciated. :)
vars
variable "realms" {
description = "realms"
type = set(string)
default = ["mrpc"]
}
variable "mrpc-groups" {
type = map(object({
name = string
realm = string
members = set(string)
}))
default = {
"0" = {
realm = "mrpc"
name = "mrpc-admins"
members = ["hellfire", "hellfire2"]
},
"1" = {
realm = "mrpc"
name = "mrpc-mods"
members = ["hellfire2"]
}
}
}
variable "mrpc-users" {
type = map(object({
username = string
email = string
first_name = string
last_name = string
realm = string
}))
default = {
"0" = {
realm = "mrpc"
username = "hellfire"
email = "bla#bla.bla"
first_name = "hell"
last_name = "fire"
}
"1" = {
realm = "mrpc"
username = "hellfire2"
email = "bla2#bla.bla"
first_name = "hell2"
last_name = "fire2"
}
}
}
resources
resource "keycloak_realm" "realm" {
for_each = var.realms
realm = each.value
}
resource "keycloak_group" "group" {
for_each = var.mrpc-groups
realm_id = each.value["realm"]
name = each.value["name"]
depends_on = [keycloak_realm.realm]
}
resource "keycloak_user" "user" {
for_each = var.mrpc-users
realm_id = each.value["realm"]
username = each.value["username"]
email = each.value["email"]
first_name = each.value["first_name"]
last_name = each.value["last_name"]
}
resource "keycloak_group_memberships" "group_members" {
for_each = keycloak_group.group
realm_id = each.value["realm_id"]
group_id = each.value["name"]
members = [ "hellfire2" ]
# i want this to be var.mrpc-groups.*.members (* used incorrectly here i think)
# if
# var.mrpc-groups.*.name == each.value["name"]
#
# so that the correct member list in the vars is used when the matching group is being looped over
# any method to get the final outcome is good :)
}
We can use the distinct and flatten functions in conjunction with a for expression within a list constructor to solve this:
distinct(flatten([for key, attrs in var.mrpc_groups : attrs.members]))
As tested locally, this will return the following for your values exactly as requested in the question indicated by var.mrpc-groups.*.members:
members = [
"hellfire",
"hellfire2",
]
The for expression iterates through the variable mrpc_groups map and returns the list(string) value assigned to the members key within each group's key value pairs. The lambda/closure scope variables are simply key and attrs because the context is unclear to me, so I was unsure what a more descriptive name would be.
The returned structure would be a list where each element would be the list assigned to the members key (i.e. [["hellfire", "hellfire2"], ["hellfire2"]]). We use flatten to flatten the list of lists into a single list comprised of the elements of each nested list.
There would still be duplicates in this flattened list, and therefore we use the distinct function to return a list comprised of only unique elements.
For the additional question about assigning the members associated with the group at the current iteration, we can simply implement the following:
members = flatten([for key, attrs in var.mrpc_groups : attrs.members if attrs.name == each.value["name"]])
This will similarly iterate through the map variable of var.mrpc_groups, and construct a list of the members list filtered to only the group matching the name of the current group iterated through keycloak_group.group. We then flatten again because it is also a nested list similar to the first question and answer.
Note that for this additional question it would be easier for you in general and for this answer if you restructured the variable keys to be the name of the group instead of as a nested key value pair.
I have already seen many threads with examples of how to do this, the problem is, I still can't do it.
All the examples have tables with extra data. For example somethings like this
lines = {
luaH_set = 10,
luaH_get = 24,
luaH_present = 48,
}
or this,
obj = {
{ N = 'Green1' },
{ N = 'Green' },
{ N = 'Sky blue99' }
}
I can code in a few languages but I'm very new to Lua, and tables are really confusing to me. I can't seem to work out how to adapt the code in the examples to be able to sort a simple table.
This is my table:
local players = {"barry", "susan", "john", "wendy", "kevin"}
I want to sort these names alphabetically. I understand that Lua tables don't preserve order, and that's what's confusing me. All I essentially care about doing is just printing these names in alphabetical order, but I feel I need to learn this properly and know how to index them in the right order to a new table.
The examples I see are like this:
local function cmp(a, b)
a = tostring(a.N)
b = tostring(b.N)
local patt = '^(.-)%s*(%d+)$'
local _,_, col1, num1 = a:find(patt)
local _,_, col2, num2 = b:find(patt)
if (col1 and col2) and col1 == col2 then
return tonumber(num1) < tonumber(num2)
end
return a < b
end
table.sort(obj, cmp)
for i,v in ipairs(obj) do
print(i, v.N)
end
or this:
function pairsByKeys (t, f)
local a = {}
for n in pairs(t) do table.insert(a, n) end
table.sort(a, f)
local i = 0 -- iterator variable
local iter = function () -- iterator function
i = i + 1
if a[i] == nil then return nil
else return a[i], t[a[i]]
end
end
return iter
end
for name, line in pairsByKeys(lines) do
print(name, line)
end
and I'm just absolutely thrown by this as to how to do the same thing for a simple 1D table.
Can anyone please help me to understand this? I know if I can understand the most basic example, I'll be able to teach myself these harder examples.
local players = {"barry", "susan", "john", "wendy", "kevin"}
-- sort ascending, which is the default
table.sort(players)
print(table.concat(players, ", "))
-- sort descending
table.sort(players, function(a,b) return a > b end)
print(table.concat(players, ", "))
Here's why:
Your table players is a sequence.
local players = {"barry", "susan", "john", "wendy", "kevin"}
Is equivalent to
local players = {
[1] = "barry",
[2] = "susan",
[3] = "john",
[4] = "wendy",
[5] = "kevin",
}
If you do not provide keys in the table constructor, Lua will use integer keys automatically.
A table like that can be sorted by its values. Lua will simply rearrange the index value pairs in respect to the return value of the compare function. By default this is
function (a,b) return a < b end
If you want any other order you need to provide a function that returs true if element a comes befor b
Read this https://www.lua.org/manual/5.4/manual.html#pdf-table.sort
table.sort
Sorts the list elements in a given order, in-place, from list[1] to
list[#list]
This example is not a "list" or sequence:
lines = {
luaH_set = 10,
luaH_get = 24,
luaH_present = 48,
}
Which is equivalent to
lines = {
["luaH_set"] = 10,
["luaH_get"] = 24,
["luaH_present"] = 48,
}
it only has strings as keys. It has no order. You need a helper sequence to map some order to that table's element.
The second example
obj = {
{ N = 'Green1' },
{ N = 'Green' },
{ N = 'Sky blue99' }
}
which is equivalent to
obj = {
[1] = { N = 'Green1' },
[2] = { N = 'Green' },
[3] = { N = 'Sky blue99' },
}
Is a list. So you could sort it. But sorting it by table values wouldn't make too much sense. So you need to provide a function that gives you a reasonable way to order it.
Read this so you understand what a "sequence" or "list" is in this regard. Those names are used for other things as well. Don't let it confuse you.
https://www.lua.org/manual/5.4/manual.html#3.4.7
It is basically a table that has consecutive integer keys starting at 1.
Understanding this difference is one of the most important concepts while learning Lua. The length operator, ipairs and many functions of the table library only work with sequences.
This is my table:
local players = {"barry", "susan", "john", "wendy", "kevin"}
I want to sort these names alphabetically.
All you need is table.sort(players)
I understand that LUA tables don't preserve order.
Order of fields in a Lua table (a dictionary with arbitrary keys) is not preserved.
But your Lua table is an array, it is self-ordered by its integer keys 1, 2, 3,....
To clear up the confusing in regards to "not preserving order": What's not preserving order are the keys of the values in the table, in particular for string keys, i.e. when you use the table as dictionary and not as array. If you write myTable = {orange="hello", apple="world"} then the fact that you defined key orange to the left of key apple isn't stored. If you enumerate keys/values using for k, v in pairs(myTable) do print(k, v) end then you'd actually get apple world before orange hello because "apple" < "orange".
You don't have this problem with numeric keys though (which is what the keys by default will be if you don't specify them - myTable = {"hello", "world", foo="bar"} is the same as myTable = {[1]="hello", [2]="world", foo="bar"}, i.e. it will assign myTable[1] = "hello", myTable[2] = "world" and myTable.foo = "bar" (same as myTable["foo"]). (Here, even if you would get the numeric keys in a random order - which you don't, it wouldn't matter since you could still loop through them by incrementing.)
You can use table.sort which, if no order function is given, will sort the values using < so in case of numbers the result is ascending numbers and in case of strings it will sort by ASCII code:
local players = {"barry", "susan", "john", "wendy", "kevin"}
table.sort(players)
-- players is now {"barry", "john", "kevin", "susan", "wendy"}
This will however fall apart if you have mixed lowercase and uppercase entries because uppercase will go before lowercase due to having lower ASCII codes, and of course it also won't work properly with non-ASCII characters like umlauts (they will go last) - it's not a lexicographic sort.
You can however supply your own ordering function which receives arguments (a, b) and needs to return true if a should come before b. Here an example that fixes the lower-/uppercase issues for example, by converting to uppercase before comparing:
table.sort(players, function (a, b)
return string.upper(a) < string.upper(b)
end)
I got params.user return the list.
Ex:
params.user = 10 20
then I used
params.user.each { id ->
}
Then id has value:
id = 10, id = 20
When params.user only returns 10, iterating over it I get 1 and 0.
So my idea is count the length() of params.user and put the condition
if (params.user == 1){
//to do something
}
But when I used params.user.length(), it returns 2 and I need it return 1. Please help
When you want to use the reserved params map, you actually use a Map. Then of course, when you do params.myParams.length(), you will get the length of your String value.
But Grails provides tools to get data from the param map. For a list use:
List myList = params.list('user')
Grails provides other ways to grab other kind of data:
def intValue = params.int('paramInt')
def shortValue = params.short('paramShort')
def byteValue = params.byte('paramByte')
def longValue = params.long('paramLong')
def doubleValue = params.double('paramDouble')
def floatValue = params.float('paramFloat')
def booleanValue = params.boolean('paramBoolean')
Last but not least, if you have complex data to bind, don't forget to use Command Objects ;)
Say that you want to create a Lua table, and all its keys are valid lua identifiers. Then you can use the key=value syntax:
local niceTable = { I=1, like=1, this=1, syntax=1 }
If however your strings are not "identifiable", then you have to use the ['key']=value syntax:
local operators = { ['*']="Why", ['+']="the", ['/']="brackets", ['?']='?' }
I'm a bit baffled about this. What are those brackets doing there? What do they mean?
They identify the contained string as a key in the resulting table. The first form, you could consider as equal to
local niceTable = {}
niceTable.I = 1;
niceTable.like = 1;
The second form is equal to
local operators = {}
operators['*'] = "Why";
operators['+'] = "The";
The difference is purely syntactic sugar, except where the first one uses identifiers, so it has to follow the identifier rules, such as doesn't start with a number and interpret-time constant, and the second form uses any old string, so it can be determined at runtime, for example, and a string that's not a legal identifier. However, the result is fundamentally the same. The need for the brackets is easily explained.
local var = 5;
local table = {
var = 5;
};
-- table.var = 5;
Here, var is the identifier, not the variable.
local table = {
[var] = 5;
};
-- table[5] = 5;
Here, var is the variable, not the identifier.
The normal syntax for indexing a table is t[val]. For string keys only, Lua provides an alternate syntax, where t.foo is exactly equivalent to t["foo"]. This is purely a syntactical convenience, so-called 'syntax sugar'. It doesn't add functionality, it just gives you a less cluttered syntax for using strings as named fields.
There are a lot of strings keys this won't work for:
t["hello_world"] => t.hello_world -- works
t["hello world"] => t.hello world -- oops, space in the string
t["5 * 3"] => t.5 * 3 -- oops
t['[10]'] => t.[10] -- oops
Basically it only works if the string key would be a valid identifier.
Again, tables are indexed via [], and in most cases you need to use them:
t = {
-- [key] = value
[10] = "ten", -- number key, string value
["print function"] = print, -- string key, function value
["sub table"] = {}, -- string key, table value
[print] = 111, -- function key, number value
["foo"] = 123, -- string key, number value
}
Only if you're using a string key which would work as a valid identifier (no spaces, contains only word characters, numbers, or underlines, and doesn't begin with a number) can you use the shortcut syntax. For the table above, that would be only 'foo':
t = {
-- [key] = value
[10] = "ten", -- number key, string value
["print function"] = print, -- string key, function value
["sub table"] = {}, -- string key, table value
[print] = 111, -- function key, number value
foo = 123, -- string key, number value
}
I have a table in lua with some data.
sometable = {
{name = "bob", something = "foo"},
{name = "greg", something = "bar"}
}
I then want to loop through the table and assign a number to each name as a variable. New to lua and tried it like this.
for i,t in ipairs(sometable) do
t.name = i
end
I was then assuming print("name1", bob) would give me name1 = 1. Right now I'm getting nil. So I'm back to my ugly static list of variables till some kind soul tells me how I'm an idiot.
> sometable = {{name = "bob", something = "foo"},{name = "greg", something = "bar"}}
> for i,t in ipairs(sometable) do t[t.name] = i end
> for i,t in ipairs(sometable) do for j,u in pairs (t) do print (j,u) end end
name bob
something foo
bob 1
greg 2
something bar
name greg
> return sometable[1].bob
1>
The ipairs function will iterate only through numerically indexed tables in ascending order.
What you want to use is the pairs function. It will iterate over every key in the table, no matter what type it is.