Static functions in immutable types...

Steven Schveighoffer schveiguy at
Tue Dec 8 06:15:56 PST 2009

On Mon, 07 Dec 2009 05:34:52 -0500, Michal Minich  
<michal.minich at> wrote:

> 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.

Let's say there was an immutable static member function which treated the  
static data members as immutable.  This means nobody else can change  
them.  This means that there cannot be any static member functions that  
are not immutable.  This means that the data members cannot be marked as  
public unless they are also marked as immutable.

In this case, the equivalent thing is to mark all static data members as  
immutable, and leave the static function as a normal function.

This is why the OP said they "don't make sense"  Although his statement  
really should be "immutable static functions don't make sense", not  
"static functions in immutable types don't make sense," as they do make  
sense, they should just not be marked as immutable.

The bug filed is absolutely a bug, it should be possible to have a normal  
static function inside an immutable type.


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