[TreeDL-users] replacement for 'readonly' keyword

[Alexey D. <de...@is...>]

Hi all,

In the next version of TreeDL I plan to replace 'readonly' keyword
with something more adequate. In fact, there are two important cases
that require keywords.

1. A value of an attribute may be set no more than once.
The second call of set-accessor causes runtime exception.
If attribute is not late, it will be set at node creation time (in constructor).

2. A value of an attribute should not be set, because it is calculated
by get-accessor. In this case, there can be no set-accessor at all,
or if set-accessor exists, it should throw UnsupportedOperationException.

Now 'readonly' keyword used for the first case, but it is slightly confusing.
I prefer to have different keywords for these cases, but can not invent them :)

In fact, the first case can be implemented using custom code for set-accessor,
but the second case is more important - it controls gneration of set-accessor.

-----
There are another case that can be implemented in custom code, but I don't know 
strict pattern and therefore don't plan to introduce keyword and translation.
This case always requires custom get-code, so overhead is not very big.
It is lazy attributes, calculated during the first call of get-accessor:

attribute T v
get {
    if( v == null ) { v = ...; }
};

With 'lazy' keyword is would be: 

attribute lazy T v
get {
    v = ...;
};
-----


Well, do you have any proposals for two new keywords?

Regards,
Alexey

-----
Alexey Demakov
TreeDL: Tree Description Language: http://treedl.sourceforge.net
RedVerst Group: http://www.unitesk.com