4 replies to this topic

[Bob]

Hi,

I've been programming my own to-do list system in ComputerCraft (TPPI, survival), and I've stumbled upon something which I suspect is a bug/omission in the Lua implementation:

When I have a function that returns multiple arguments (for instance, term.current().getCursorPos()), and I want to directly use the results by putting them into a table like so:

ct = term.current()
local cy = {ct.getCursorPos()}[1]

I get the following error:

bios:366: [string "board"]:(line nr. of the "local cy..." line): unexpected symbol

While the Lua documentation states that this code should work, on this page, quoting:

function foo0 () end				  -- returns no results
function foo1 () return 'a' end	   -- returns 1 result
function foo2 () return 'a','b' end   -- returns 2 results

Quote

A constructor also collects all results from a call, without any adjustments:

a = {foo0()}		 -- a = {}  (an empty table)
a = {foo1()}		 -- a = {'a'}
a = {foo2()}		 -- a = {'a', 'b'}

Am I doing something wrong, perhaps misreading the documentation? Or is this a bug?

[Dragon53535]

local cy = {ct.getCursorPos()}[1] --# This little [1] is invalid.

Can't do this...

local cy = {ct.getCursorPos()}

Works, however if you're wanting to only have the first index as a table to hold the data you need to do this:

local cy = {}
cy[1] = {ct.getCursorPos()}

Edited by Dragon53535, 29 December 2014 - 03:12 PM.

[Lyqyd]

The first index won't get you a "y" value of any sort anyway. If I recall correctly, this may work:

local cy = ({ct.getCursorPos()})[2]

[Lignum]

Dragon53535, on 29 December 2014 - 03:12 PM, said:

local cy = {ct.getCursorPos()}[1] --# This little [1] is invalid.

Can't do this...

local cy = {ct.getCursorPos()}

Works, however if you're wanting to only have the first index as a table to hold the data you need to do this:

local cy = {}
cy[1] = {ct.getCursorPos()}

You can also do this:

local cy = ({ ct.getCursorPos() })[1]

EDIT: Ninja'd

Edited by Lignum, 29 December 2014 - 03:29 PM.

[MKlegoman357]

To explain why that didn't work: Lua just doesn't let you index a table directly after it's constructor ( { ... } ) so you have to enclose it in parenthesis if you want to do that:

local t = {1, 2, 3}[2] --// wrong way

local t = ({1, 2, 3})[2] --// right way