CTFE & code generators based on PEG grammars?

[ag0aep6g]

On 06.04.19 16:19, Alex wrote:
> That is CTFE is CT RTFE where runtime functions are executed at compile 
> time when the inputs are CT.

You may have the right idea, but the last part of that sentence is 
wrong/misleading. CTFE happens when the result is required at CT. The 
inputs must be available at CT, but that alone doesn't trigger CTFE.

Examples:

----
bool f(string s) { return __ctfe; }
void main()
{
     import std.stdio: readln;
     enum x = f("foo"); /* CTFE */
     enum y = f(readln()); /* error, because "readln" can't be CTFEd */
     auto z = f("foo"); /* not CTFE */
}
----