On Friday, 21 February 2014 at 13:38:58 UTC, Gopan wrote:
Attempting to learn CTFE, I tried the following test.
size_t counter;
uint Test()
{
if (!__ctfe)
{
++counter;// This code is for execution at run time
}
return 2;
}
void main()
{
writeln("counter = ", counter);
immutable int n = Test();
As this is a local variable, this is a runtime initialization, no
__ctfe here. Doesn't matter that it's immutable. It's
static/global vs local. So, this correctly does ++counter.
Make it static immutable n, and counter won't be incremented.
int[n] arr;
Not sure if this should compile. n is a run-time value. It just
happens that it can be CTFE'd. A more problematic case:
---
void main()
{
immutable n = __ctfe ? 1 : 2;
int[n] a;
assert(a.length == n); // fails, wat
}
---
writeln("arrary length = ", arr.length, " ; counter = ",
counter);
}
output:
counter = 0
arrary length = 2 ; counter = 1
For array declaration to be successful, its size has to be
known at compile time. The above code compiles too. But
__ctfe seems to be false while performing Test().
Instead, if I write
int[Test()] c;
writeln("c.length = ", c.length, " ; counter = ", counter);
output is
counter = 0
c.length = 2 ; counter = 0
What is wrong in my mind?
Thanks,
Gopan
