08-Sep-2013 02:57, Xinok пишет:
For me, one of the annoyances of working with immutable data is simply
initializing data. Immutable variables have to be initialized upon
declaration and cannot be modified after that point. This is made more
difficult if you have several immutable variables to initialize in
conjunction with one another
[snip]
An impractical example:
void foo()
{
immutable
{
int[] arr = ...;
int[] arr2 = arr.dup;
sort(arr); // arr is still mutable
int[] arr2 = arr.dup;
reverse(arr2);
arr ~= arr2;
}
sort(arr); // Error is thrown because arr is now immutable
}
A pure lambda can achieve the same unless, of course, purity is out of
question:
immutable arr = {
int[] arr = ...;
int[] arr2 = arr.dup;
sort(arr); // arr is still mutable
int[] arr2 = arr.dup;
reverse(arr2);
arr ~= arr2;
return arr;
} pure ();
But if you don't require purity you may escape a mutable reference
somewhere (from within the immutable block where it is mutable):
int[] global;
{
immutable
{
int[] arr = ...;
global = arr;
}
... whopse now immutable arr can be changed elsewhere...
}
Basically even not yet completely outlined the feature already pulls in
escape analysis. Not going to fly IMHO.
--
Dmitry Olshansky
