C#•4y ago

❔ Best way to create a unique key made out of x y integer coordonates for a dictionary

Hello, i want to create a unique key to access values in a Dictionary, this key has to be unique and able to be created using just simple x y integer type coordonates. Any help is appreciated. Thank you

sibber•12/7/22, 2:54 PM

why not make the coordinate

Ssibber why not make `TKey` the coordinate

BirdmanOP•12/7/22, 3:05 PM

not sure i follow

sibber•12/7/22, 3:06 PM

Ssibber `Dictionary<Coordinate, Whatever>`

BirdmanOP•12/7/22, 3:07 PM

but let's say i make a Coordonate(1, 2) and then create a new Coordonate(1, 2) object to access that value, would it work?

sibber•12/7/22, 3:08 PM

if they return the same hash code then yes

Ssibber if they return the same hash code then yes

BirdmanOP•12/7/22, 3:10 PM

but would they retun the same hash code? like if i do
Coordonate(1, 2)
Coordonate(1, 2)
would both have same hash?

sibber•12/7/22, 3:11 PM

i mean you should override

ero•12/7/22, 3:11 PM

If you implement the method, sure

sibber•12/7/22, 3:11 PM

or preferably make it a record

ero•12/7/22, 3:11 PM

Definitely make it a record

ero•12/7/22, 3:11 PM

A ValueTuple might just be enough

ero•12/7/22, 3:11 PM

But less concrete

Ssibber i mean you should override `GetHashCode`

BirdmanOP•12/7/22, 3:13 PM

but don't i have to manually generate the hash myself to always get a unique one based on the coordonates?

sibber•12/7/22, 3:14 PM

is a method from

sibber•12/7/22, 3:14 PM

you just override it in the class/struct

sibber•12/7/22, 3:14 PM

or use a record

sibber•12/7/22, 3:15 PM

which does it for you, as well as implementing value equality and other things

Ssibber you just override it in the class/struct

BirdmanOP•12/7/22, 3:16 PM

okay sure, i get that, but my issue is how do i generate that hash so it's unique but also recreatable from the coordonates

D.Mentia•12/7/22, 3:16 PM

also if it's a struct you're already done; as long as the values match it's equal

BBirdman okay sure, i get that, but my issue is how do i generate that hash so it's uniqu...

sibber•12/7/22, 3:16 PM

you dont, does

ero•12/7/22, 3:16 PM

The whole point is that it is recreatable

ero•12/7/22, 3:17 PM

You implement the creation

D.Mentia•12/7/22, 3:17 PM

Hashcodes are kindof a whole separate thing that you don't really need to know anymore because of records

D.Mentia•12/7/22, 3:17 PM

Just use a struct, or a record, and it'll do the job

DD.Mentia also if it's a struct you're already done; as long as the values match it's equa...

sibber•12/7/22, 3:17 PM

not exactly

D.Mentia•12/7/22, 3:18 PM

? That's how value types work, right? And structs are always value types?

ero•12/7/22, 3:19 PM

Only if they're unmanaged

ero•12/7/22, 3:19 PM

As in, fit the unmanaged constraint

ero•12/7/22, 3:20 PM

If the struct contains a reference type, it won't work

D.Mentia•12/7/22, 3:20 PM

Oh yeah, that's fair

MODiX•12/7/22, 3:20 PM

Cyberrex#8052

REPL Result: Success

Console Output

Compile: 462.573ms | Execution: 68.553ms | React with ❌ to remove this embed.

ero•12/7/22, 3:20 PM

String is the exception of course

D.Mentia•12/7/22, 3:21 PM

Though I think the real answer to this question is, don't use a Dictionary, use a 2d array. There's no advantage to using a Dictionary for this, I don't think? Since there is a known lower and upper bound, and it's already integers, the 2d array lookup would be just as fast as a dictionary (or faster, since you're not making a Coordinate)

sibber•12/7/22, 3:22 PM

not really, it depends on what theyre trying to do

D.Mentia•12/7/22, 3:23 PM

(a 2d array also means you could do things like, binary search to find the entity that is closest to a given coordinate...? Maybe. I've been thinking about a similar implementation)

DD.Mentia Though I think the real answer to this question is, don't use a Dictionary, use ...

BirdmanOP•12/7/22, 3:23 PM

hmm, how much slower would be iterating through a 100000x100000 array vs a dictionary with a much smaller list of coordonates?

Eero String is the exception of course

sibber•12/7/22, 3:23 PM

how are they an exception in this case?

BirdmanOP•12/7/22, 3:23 PM

cause i have to iterate through the whole thing

sibber•12/7/22, 3:24 PM

probably faster than a dictionary

D.Mentia•12/7/22, 3:24 PM

I've been told you should never iterate a dictionary, but I don't know how bad it is if you do

sibber•12/7/22, 3:24 PM

oh wait smaller?

sibber•12/7/22, 3:24 PM

depends, benchmark it

DD.Mentia I've been told you should never iterate a dictionary, but I don't know how bad i...

sibber•12/7/22, 3:24 PM

i mean yeah a dictionary isnt meant to be iterated

D.Mentia•12/7/22, 3:24 PM

If you're iterating it, why do you need to be able to lookup the value?

sibber•12/7/22, 3:25 PM

iterating it will be relatively slow

BirdmanOP•12/7/22, 3:25 PM

huge mostly empty array vs a dictionary with lets say 20% of the values in the 2d array

DD.Mentia If you're iterating it, why do you need to be able to lookup the value?

BirdmanOP•12/7/22, 3:25 PM

to remove values from it

BirdmanOP•12/7/22, 3:25 PM

and also add

sibber•12/7/22, 3:25 PM

i think having a coordinate type and a dictionary makes more sense

BirdmanOP•12/7/22, 3:25 PM

and also build something from it, that's why i have to iterate through all of it