Bidirectional range dilemma

[Peter Alexander]

On Sunday, 13 January 2013 at 14:01:28 UTC, bearophile wrote:
> Safety on default and speed on request is one of the tenets of 
> D language. And it's a good thing.
>
> Not allocating a buffer for each permutation is premature 
> optimization.

You may have convinced me. I'll need to think more about it.

FWIW, it is not a premature optimisation. On a simple benchmark I 
did, adding .dup to front() increased runtime by 3.5x on DMD with 
all optimisations. 3.5 is the difference between C and Javascript 
in the Computer Language Benchmarks Game.

http://benchmarksgame.alioth.debian.org/u32/which-programs-are-fastest.php

I do care about safety, but I also believe that performance is 
critically important to D's success. Performance on demands is 
good in theory, but if I'm writing high performance code then I 
want performance by default, and I don't want to have to fill my 
code with annotations and special flags/options.

I think we need a D mission statement that we can refer to, to 
settle these disputes. How much performance loss is acceptable in 
the name of safety by default?