immutable bug?

[Kagamin]

On Sunday, 12 January 2014 at 02:11:18 UTC, Manu wrote:
> Also, I was under the impression a 'strongly pure' function's 
> arguments
> only need to be const, not necessarily immutable. Purity says 
> something
> about the transformation performed by the function, nothing 
> about the data
> it operates on.
> Why should all arguments need to be immutable?

Your definition of purity states it clearly that the purity 
depends on the mutability of the input data.