25.12.2011 0:48, Mr. Anonymous пишет:
Actually, when I think of it:
int a_orig = a++;
int[] arr_orig = arr[]++;
Should be read as:
int a_orig = a;
++a;
int[] arr_orig = arr[];
++arr[];
(If I'm not mistaken, it was written in the TDPL book)
Which means no copy of arr is made, and both arrays (which reference to
the same block) are affected.
OK. As I wrote: "Yes, this allocation sometimes can be optimized out but
not always.". Consider this:
---
void main()
{
int[] a = new int[5];
void f(int[] b)
{
// Here we assume that b is unchanged a.
// As these array differ we need a copy.
assert(b[0] == 0);
assert(a[0] == 1);
}
f(a[]++); // Note: compilation error now
}
---
Why not to rewrite `f(a[]++);` as `f(a); ++a[];`? Because postincrement
is expected to increment its argument when it is executed. It just
returns an unchanged copy. Analogous D code with integers illustrates this:
---
void main()
{
int a;
void f(int b)
{
assert(b == 0);
assert(a == 1);
}
f(a++);
}
---
