Dear,
I started to make an API, and wanted to get my api see errors and tell the user the reason,
The problem is that i have no idea how to let my program recognize if a label is a
number, string or a table. Also, is there a function to let a function recognize if a label exists?
Please help!
-- ExPfiGHtEr080
0
Label format recoqnition
Started by ExPfiGHtEr080, Jan 24 2014 02:51 PM
3 replies to this topic
#1
Posted 24 January 2014 - 02:51 PM
#2
Posted 26 January 2014 - 03:39 AM
Do you mean a computer label? There is a os.getComputerLabel() function which returns the label. If it hasn't been set, it will be nil.
There is a type() function in Lua that can tell you what type a variable is.
This program will output:
As for existence, if a variable is nil, it is false. If it is assigned it will evaluate as true.
So, you can test a variable. Ex.
This is useful in Lua, because it allows you to assign values in functions when they are nil:
For additional error checking, you may want to check out the pcall() function (protected call) and the assert() function.
For assert and a useful website, check The.Lua.Tutorial. You can try out Lua commands there interactively, or just use the Lua interactive mode in ComputerCraft (see Computer Basics 1 by Lyqyd
Does that point you in the right direction?
There is a type() function in Lua that can tell you what type a variable is.
myVar = 1 print (type(myVar)) myVar = "1" print (type(myVar)) myVar = {} print (type(myVar)) local myNewVar --note no value assigned print(type(myNewVar)) print(type(undeclaredVariable))
This program will output:
number string table nil nil
As for existence, if a variable is nil, it is false. If it is assigned it will evaluate as true.
So, you can test a variable. Ex.
local myVar if myVar then print "It exists" else print "Nope, it is nil." end --Result --Nope, it is nil.
This is useful in Lua, because it allows you to assign values in functions when they are nil:
local myEmptyVar local myOtherVar = 3 myEmptyVar = myEmptyVar or 10 myOtherVar = myOtherVar or 25 print(myEmptyVar) print(myOtherVar) --Result --10 --3
For additional error checking, you may want to check out the pcall() function (protected call) and the assert() function.
For assert and a useful website, check The.Lua.Tutorial. You can try out Lua commands there interactively, or just use the Lua interactive mode in ComputerCraft (see Computer Basics 1 by Lyqyd
Does that point you in the right direction?
Edited by surferpup, 26 January 2014 - 03:51 AM.
#3
Posted 26 January 2014 - 08:16 AM
surferpup, Thank you so much! thats exactly what i needed Ill look at you when i need more help
#4
Posted 26 January 2014 - 04:59 PM
Lot of amazing coders who give great advice on this site. Just saying.
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