[erlang-questions] Arithmetic expressions [WAS: Re: Binaries problem]

[Jim Thompson]

Kostis Sagonas wrote:
> Jim Thompson wrote:

>> Eshell V5.5.2  (abort with ^G)
>> 1> round(math:pow(2,21))-3.
>> 2097149
> 
> Unrelated to the topic, but we had weird cases where the HiPE compiler 
> was crashing when compiling binaries in R11B-3.  They were all related 
> to use of an expression that was similar to the one Jim is using:
> 
>     round(math:pow(2,N)) - K.
> 
> In examining the problem, we realized that this was a very stupid way of
> denoting this quantity.  We solved the problem (in R11B-4) by adopting a 
> much better (and significantly faster) way of writing the same 
> expression in Erlang:
> 
>     (2 bsl (N-1)) - K
> 
> I suspect this "round + math:pow(2)" combination is not so uncommon 
> after all ... although there is really no reason to use it.

I am an Erlang newbie, and therefore stupid.   Ignore what I say, or type.