Functions that I find useful

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#1

I was looking through the Bulletin Board and I came across this post
Table.filter function - Bulletin Board - Developer Forum | Roblox

But it is kind of messy so I made it a little bit better (It also has typechecking)

-- Filters a table based on a predicate function.
local function filter<K, V>(table : {[K]: V}, callback : (K, V) -> boolean) : {[K]: V}
	local result = {}
	
	for i, v in table do
		if callback(i, v) then
			result[i] = v
		end
	end
	
	return result
end

And also the compare function

local function compare(x, ...)
	return table.find({...}, x) ~= nil
end

It just simplifies your if statements so instead of doing this

if foo == bar and foo == baz and foo == qux then
    -- ...
end

You can do this

if compare(foo, bar, baz, qux) then
    -- ...
end

I know this isn’t a lot but I thought it would be helpful for some people so there you go

2 Likes
#2

Creating an array just for comparisons then doing a table.find call doesn’t seem quite fast though, in alot of cases doing it the traditional way would be miles faster… And for filter, just don’t put in incorrect elements in the first place. But if your code doesn’t need to be fast and maybe you like js, this is a pretty solid post.

Heres a function I’d like to add which I use quite alot:

local function jumpTable<T..., R...>(cases: {[any | "_"]: (T...) -> (R...)}) -> (caseItem: any, T...) -> (R...)
     return function(case, ...) 
         local handler = cases[case]
         if handler then return handler(...) end
         local default = cases._
         if not default then return end
         return default(...) -- Default case
     end
end

It is essentially a switch statement; you can do this:

local jump = jumpTable {
    Monday = function() print("It Is Monday") end,
    Tuesday = function() print("It Is Tuesday") end,
    _ = function() warn("Unknown day") end
}

jump("Monday")
jump("Saturday") -- Unknown day

It is quite nice for places where you have alot of possible values for something, makes it faster but also reduces overall nesting