On Monday, 1 October 2012 at 17:53:35 UTC, Tommi wrote:
On Monday, 1 October 2012 at 08:00:47 UTC, Jakob Ovrum wrote:
The only real problem here is that you wrote a function called
pow2 that effectively returns 6 unconditionally. I doubt your
math professor would be particularly impressed. If you had
used __ctfe properly, it would return the same value both at
compile-time and runtime. At present, __ctfe is a necessary
evil as CTFE can be severely crippled without it.
I solemnly swear not to use __ctfe improperly. But my problem
with it is, that there *exists* the possibility of improper use
of __ctfe.
Can you name a programming language that supports CTFE, but
doesn't allow the possibility of misuse?
Actually, can you name any language with a safety or purity
feature that cannot be thwarted by a motivated programmer?
To echo Jonathan's sentiment, no programming language can stop a
programmer who is determined to write stupid code from doing so.
For the sake of discussion, here's an example of a pure function
in Haskell (arguably the "purest" language in wide use today)
that happily returns a random integer every time it is called.
import System.IO.Unsafe
import System.Random
pureFunction :: () -> Int
pureFunction x = unsafePerformIO impureInside
where impureInside = getStdRandom (randomR (1,6))
main = do
print (pureFunction ())
print (pureFunction ())
print (pureFunction ())
This prints three random integers between 1 and 6 when executed.
-- Graham
