Small Useful Functions

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Robin
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Re: Small Useful Functions

Post by Robin » Wed May 28, 2014 9:28 am

It also might not add them in the order you want to -- if you want the values from the other table added in order, use ipairs.
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szmol96
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Re: Small Useful Functions

Post by szmol96 » Wed May 28, 2014 4:57 pm

Gotcha.
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Doctory
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Re: Small Useful Functions

Post by Doctory » Tue Sep 30, 2014 4:50 pm

Code: Select all

requirei = local function(d, ...)
	args = {...}
	for k, i in ipairs(args) do
		file = d .. i
		require(file)
	end	
end
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Robin
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Re: Small Useful Functions

Post by Robin » Tue Sep 30, 2014 10:26 pm

Or:

Code: Select all

local function requirei(d, ...)
	for i, v in ipairs{...} do
		require(d .. v)
	end	
end
,

which has the advantage of not overwriting or leaking the globals args and file. Also this doesn't contain a syntax error on the first line.
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Doctory
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Re: Small Useful Functions

Post by Doctory » Wed Oct 01, 2014 12:43 pm

i suppose this would be helpful as well:

Code: Select all

local function clear(t)
	for i,_ in ipairs(t) do
		table.remove(t, i)
	end
end
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Robin
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Re: Small Useful Functions

Post by Robin » Wed Oct 01, 2014 1:26 pm

That function is both ineffective and inefficient: it only removes half of the items, and it takes 4 times as long for a table that's 2 times as big.

Better would be:

Code: Select all

local function clear(t)
	for i = #t, 1, -1 do
		t[i] = nil
	end
end
This removes all the items, without shuffling them around.
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davisdude
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Re: Small Useful Functions

Post by davisdude » Wed Oct 01, 2014 11:53 pm

Hopefully there's nothing wrong with this one (just to keep Robin's job a little easier ;))

Code: Select all

local function RemoveHole( Table ) -- Removes nils from tables.
	local New = {}

	for Index, Value in pairs( Table ) do
		New[Index] = Value
	end
	
	return New
end
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micha
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Re: Small Useful Functions

Post by micha » Thu Oct 02, 2014 6:01 am

Robin wrote:Better would be:

Code: Select all

local function clear(t)
	for i = #t, 1, -1 do
		t[i] = nil
	end
end
If you remove all of the entries, then you don't even need to traverse the table backwards. This works, too:

Code: Select all

local function clear(t)
	for i = 1,#t do
		t[i] = nil
	end
end
davisdude wrote:Hopefully there's nothing wrong with this one (just to keep Robin's job a little easier ;))

Code: Select all

- snip -
What exactly should this function do? What do you mean by "remove nils values?" A variable with value "nil" does not exist. So if you have a nil-value in a table then the key-value pair does not exist. Assigning nil to a variable is a way to delete variable.

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Re: Small Useful Functions

Post by davisdude » Thu Oct 02, 2014 10:54 pm

Ya know, I'm not even sure what I was thinking when I wrote that.
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Sapper
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Re: Small Useful Functions

Post by Sapper » Mon Oct 06, 2014 4:36 pm

Heres a few, kinda useful for tetris type games and map generating

new array

Code: Select all

function newAr(h,w)
	local ar = {}
	for i=1,h do
		ar[i] = {}
		for j=1,w do
			ar[i][j] = 0
		end
	end
	return ar
end
transpose array

Code: Select all

function transpose(ar)
	local ar2 = newAr(#ar,#ar[1])
	for i=1,#ar do
		for j=1,#ar[i] do
			ar2[j][i] = ar[i][j]
		end
	end
	return ar2
end
flip array

Code: Select all

function vFlip(ar)
	local ar2 = newAr(#ar,#ar[1])
	for i=1,#ar do
		for j=1,#ar[i] do
			ar2[#ar - i + 1][j] = ar[i][j]
		end
	end
	return ar2
end

function hFlip(ar)
	local ar2 = newAr(#ar,#ar[1])
	for i=1,#ar do
		for j=1,#ar[i] do
			ar2[i][#ar[i]-j + 1] = ar[i][j]
		end
	end
	return ar2
end
and then rotate array

Code: Select all

function rotLeft(ar)
    return vFlip(transpose(ar))
end

function rotRight(ar)
    return hFlip(transpose(ar))
end

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