mutable, const, immutable guidelines

[qznc]

On Wednesday, 16 October 2013 at 20:33:23 UTC, H. S. Teoh wrote:
> I'm of the view that code should only require the minimum of 
> assumptions
> it needs to actually work. If your code can work with mutable 
> types,
> then let it take a mutable (unqualified) type. If your code 
> works
> without modifying input data, then let it take const. Only if 
> your code
> absolutely will not work correctly unless the data is 
> guaranteed to
> never change, ever, by anyone, should it take immutable.

What about functions, which are not thread-safe?

auto percentageDistribution(const int[] percentages) {
   [...]
   assert (sum == 100);
   [...]
}

Not a realistic example, but it should do. This function checks 
that the sum of all percentages equals 100, but a concurrent 
modification might break this. You could require an immutable 
array to avoid that. Alternatively, the absence of "shared" could 
be considered enough to express this.