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Filipe_Br
Master Cheater
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Joined: 07 Jan 2016
Posts: 272
Location: My house
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 Posted: Sat Jul 01, 2017 9:09 pm Post subject: How do I know if an address is allocated? |
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In Lua I have a list with addresses, what interests me in them is to read its value with 'readInteger ()', however it has a problem, some of these addresses are sometimes not allocated, that is, they get the value = ??.
When I make a comparison to the value of these invalid addresses I get an error.
How can I check if this address is allocated and stop receiving errors?
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Zanzer
I post too much
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Joined: 09 Jun 2013
Posts: 3278
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| Posted: Sun Jul 02, 2017 12:43 pm Post subject: |
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| Code: | local value = readInteger(address)
if value and value > 0 then
-- yay
end |
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FreeER
Grandmaster Cheater Supreme
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Joined: 09 Aug 2013
Posts: 1091
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| Posted: Sun Jul 02, 2017 5:22 pm Post subject: |
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@Zanzer, why value > 0? After all normal values could legitimately be negative...
example explanation stuff:
| Code: | address = "5"
local value = readInteger(address)
print(tostring(value))
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where an address of 5 is obviously bad shows that the return value is nil (and doesn't create an error that stops the script unlike, say, getAddress("[5]")) which would be caught by the if value check since nil is treated as a false value.
Alternatively if you have a memory record and access it's value then it will be "??"
| Code: | al = getAddressList()
mr = al.getMemoryRecord(0) -- get first record in list for testing, again address of 5
print(tostring(mr.value)) -- ??
print(tostring(mr.value == "??")) -- true
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Zanzer
I post too much
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Joined: 09 Jun 2013
Posts: 3278
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| Posted: Mon Jul 03, 2017 2:23 pm Post subject: |
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You said you wanted to "make a comparison" so value > 0 was an example of a comparison.
The important part was before it. It checks to make sure it's not nil. | Code: | if value then
-- do stuff
end |
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