Interesting rant about Scala's issues

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On Friday, 4 April 2014 at 01:51:58 UTC, Walter Bright wrote:
> Since in D you can detect if a function is pure, and specialize 
> accordingly, it is not necessary to require that the filter 
> function be pure.

That's true, but then somebody somewhere accidentally passes in a 
delegate that references some outside state, and performance is 
suddenly shot for no apparent reason. The upside in D is that you 
can explicitly mark delegates as pure and have the compiler check 
for you, but that still puts the onus on the user to be 
disciplined and not forget.