Extended Type Design.

[Frits van Bommel]

Andrei Alexandrescu (See Website For Email) wrote:
> Benji Smith wrote:
>> I vote for "readonly" and "const". Anything else seems like a mistake.
> 
> Which is which? How would you have people distinguish them without 
> running to the manual? How would you explain C++ immigrants that const 
> is actually readonly, and there is a const, but that const means 
> something else than their const?

How would you have people distinguish char/wchar/dchar without running 
to the Unicode standard to see which characters they can hold in a 
single unit?
Or short/int/long or float/double/real without running to the standard 
to look up the ranges and precision of those data types?

How would you explain to the average person from the 
Netherlands/Estonia/Finland/Germany/Slovakia[1] 'auto' doesn't have 
anything to do with transportation?
How would you explain to Dutchmen that 'long' doesn't have anything to 
do with breathing air? (Hint for all you foreigners out here: the Dutch 
word 'long' translates to 'lung' :P )

Some things are somewhat arbitrary conventions.
When you learn a new language, some words will mean different things, 
with other words that have the meaning you're used to.
It happens ;).

[1]: See http://dictionary.reference.com/search?q=car , specifically the 
first set of translations, roughly halfway down the page




Seriously though:
"readonly" would mean that you (meaning any code that can access the 
symbol so declared) can only read data referenced through it, but 
someone else _may_ be able to write to it[2].
"const" would mean it's just that: constant. *Nobody* can write to it.
Seems pretty easy to explain to me.

The only caveat I see is that "readonly" would mean the object itself 
can still be modified, as opposed to final. I don't see how calling it 
"const" would fix that, though.


[2]: Or of course that same code may be able to write to it, if for 
whatever reason it also has access to a mutable reference to the same data.