Static functions in immutable types...

Michal Minich michal.minich at
Mon Dec 7 02:34:52 PST 2009

Hello Tomek,

> ... don't make sense. So is there a reason why they aren't excluded
> from  the "everything in an immutable is immutable" rule?
> Tomek

Immutable static member function could be useful...

marking struct or class as const or immutable is the same as marking every 
its member so. The problem I see is in definition of what const or immutable 
member function means:

from D specs: "Immutable member functions are guaranteed that the object 
and anything referred to by the this reference is immutable."

Which applies both to instance and s static functions. I think the above 
definition should apply only to instance functions. Static const or immutable 
functions should  be defined as:

Immutable static member functions are guaranteed that the static variables 
of object and anything referred to by these variables is immutable.

static member function cannot modify member variables already, because they 
do not have this pointer. They would be only allowed to modify its arguments 
and global variables; they would be something like pure functions for the 
congaing type, but not for other world.

I'm not sure how this semantics could be useful in practice, but it seems 
definitely better to me than erroring out on static function inside immutable 

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