Also no syntax is good until proven performant. Ko...

# pattern-matching

[raulraja]

Also no syntax is good until proven performant. Kotlin currently optimizes many when into table switches indexed that are very fast

[Nico]

This surprised me a lot because I did not know such a thing was possible in the JVM! I took a look at some bytecode generated from a when and all I see are chained instanceof calls. Did you mean this or am I missing something? I thought you meant a jump table that's constant time (much like haskell's pattern matching or a C switch statement)

[Nico]

As in a lookup table

[raulraja]

what happen if you use when over ints?

[Nico]

I am using when. I am looking at bytecode generated from a when

[Nico]

OHH i misread you 1sec

[raulraja]

I mean in the case when the subject is an int or a primitive value

[Nico]

Yeah no that's a proper jump table that's fine

[Nico]

Ok I just wanted to confirm it was impossible to do it with instanceof types instead of primitives with the instruction set we have in java 6+ currently

[Nico]

Cheers!

[raulraja]

so the trick is that you can change those instance of for actual indexes of int

[raulraja]

esentially is like an enumeration

[raulraja]

every node of the tree is am int and then based on where you hit you cast it and decompose the structure in nested ifs that return null if there is no match

[raulraja]

instanceof is fast too, this would be a micro optimization

[Nico]

That's clever! but yes for the average case it's not an issue