Can you pass boolean values as command line arguments?

ChaosNicro #1

ChaosNicro's profile picture

15 posts

Location The Void

Posted 17 April 2016 - 09:30 PM

Hello there,

I am trying to write a program that is supposed to take boolean type values as arguments.
When all the statements relating to these boolean values were considered true regardless of the input, I discovered that they had been picked up as strings instead.
I then solved this by using this construct:


if arg[2] == "false" then
   local direction = false
else
   local direction = true
end

I know it's considered a strength that Lua automatically assigns types to variables but is there a way to force a certain type?
Maybe I am better of using a different input and comparing to the strings.

Thanks in advance

Creator #2

2679 posts

Location You will never find me, muhahahahahaha

Posted 17 April 2016 - 09:56 PM

Only strings.

Your solution does the job, so don't worry about it.

Lupus590 #3

Lupus590's profile picture

2427 posts

Location UK

Posted 17 April 2016 - 10:20 PM

a better solution would be


local direction --# otherwise this is local to the if statement
if arg[2] == "true" then
  direction = true
elseif arg[2] == "false" then
  direction = false
else
  --#insert some way to handle a bad argument
end

Edited on 17 April 2016 - 08:20 PM

MKlegoman357 #4

1140 posts

Location Kaunas, Lithuania

Posted 17 April 2016 - 10:46 PM

ChaosNicro, on 17 April 2016 - 09:30 PM said:
I know it's considered a strength that Lua automatically assigns types to variables…

It's the shell program that parses the arguments and gives you a string, not Lua. There's no such thing as 'automatically assign a type to a variable'. Just wanted to put away this misconception you might have had :)/>

Bomb Bloke #5

Bomb Bloke's profile picture

7083 posts

Location Tasmania (AU)

Posted 18 April 2016 - 12:01 AM

Well, there's no static typing, at least.

Anyway, another way of writing it:

local direction = arg[2]:lower() == "true"

ChaosNicro #6

ChaosNicro's profile picture

15 posts

Location The Void

Posted 18 April 2016 - 10:41 AM

Alright, thanks everyone.
That problem solved! ^_^/>

greygraphics #7

greygraphics's profile picture

16 posts

Posted 15 May 2016 - 05:37 PM

You could also use


local direction = (args[2] == "true" and true) or (false)

Lyqyd #8

Lyqyd's profile picture

8543 posts

Posted 15 May 2016 - 08:01 PM

That's redundant, though. Bomb Bloke's answer is simple and results in the same values being returned, but accepts all capitalization combinations of "true" as true.