How about a 100% CTFE?

[Gor Gyolchanyan]

> now what is the value of a ? At run time ? At compile ime ? If some other CTFE uses a ? If a CTFE from another module uses a or worse, update it ?

Run-time: Whatever _a_ ends up with by the time CTFE is done. There's
a very handy _COUNTER_ macro in Visual C++ compiler, that uses this
very feature internally.
Compile-time: The same, that it would have if run in run-time:
sequentially updated after the compile-time value (naturally).

> What the hell this program is supposed to print at run time ?

Assuming that somefunction was never called, this would print -1.
That's because _a_ has a resulting compile-time value if -1 due to
having decremented once by the someotherfunction() inside the static
if and b is being initialized by -1.

I don't see any problems in either of these cases.
The whole point of a mutable compile-time value is to have essentially
two values, one of which is computed at compile-time and the other,
which is statically initialized by the first one.

On Mon, Nov 7, 2011 at 6:14 PM, deadalnix <deadalnix at gmail.com> wrote:
>
> module a;
>
> int a = 0;
>
> int somefunction() {
>        a++;
>        return a;
> }
>
> static if(somefunction() == 1) {
>        // Some code
> }
>
> now what is the value of a ? At run time ? At compile ime ? If some other CTFE uses a ? If a CTFE from another module uses a or worse, update it ?
>
> exemple :
>
> module b;
>
> import a;
>
> int someotherfunction() {
>        a--;
>        return a;
> }
>
> static if(someotherfunction() < 10) {
>        // Some code
>
>        import std.stdio;
>
>        immutable int b = somefunction();
>        static this() {
>                writeln(b);
>        }
> }
>
> What the hell this program is supposed to print at run time ?
>
> Le 07/11/2011 14:35, Gor Gyolchanyan a écrit :
>>
>> Can you show an example of when CTFE modifies the state of the program
>> and when it's impossible to perform at run-time, provided, that it's a
>> separate compiler-aware run-time.
>>
>>> CTFE must be limited to functions with no side effect, or with side effect that are known and manageable.
>>
>> Why? There are tons of applications for CTFE other, then initializing variables.
>>
>> On Mon, Nov 7, 2011 at 5:25 PM, deadalnix<deadalnix at gmail.com>  wrote:
>>>
>>> This doesn't make any sens.
>>>
>>> Function can modify the state of the program in a non repeatable way, thus
>>> compile time function execution isn't possible for thoses.
>>>
>>> CTFE must be limited to functions with no side effect, or with side effect
>>> that are known and manageable.
>>>
>>> Le 07/11/2011 14:13, Gor Gyolchanyan a écrit :
>>>>
>>>> After reading
>>>>
>>>>     http://prowiki.org/wiki4d/wiki.cgi?DMDSourceGuide
>>>>     https://github.com/gor-f-gyolchanyan/dmd/blob/master/src/interpret.c
>>>>
>>>> I had a thought:
>>>> Why not compile and run CTFE code in a separate executable, write it's
>>>> output into a file, read that file and include it's contents into the
>>>> object file being compiled?
>>>> This would cover 100% of D in CTFE, including external function calls
>>>> and classes;
>>>> String mixins would simply repeat the process of compiling and running
>>>> an extra temporary executable.
>>>>
>>>> This would open up immense opportunities for such things as
>>>> library-based build systems and tons of unprecedented stuff, that I
>>>> can't imagine ATM.
>>>
>>>
>