Well yes, due to the halting problem, we can't detect if a function will diverge or not. It's on the behalf of the library user. However, we could limit the number of iteration or recursion to an arbitrary number.

On 01/29/2014 11:39 AM, Gábor Lehel wrote:
Ah, so `fail!()` is not okay, but `loop { }` is okay.


On Wed, Jan 29, 2014 at 11:26 AM, Pierre Talbot <[email protected] <mailto:[email protected]>> wrote:

    It's a diverging function in the sense of the manual:
    http://static.rust-lang.org/doc/master/rust.html#diverging-functions

    On 01/29/2014 11:21 AM, Gábor Lehel wrote:

        On Wed, Jan 29, 2014 at 10:19 AM, Pierre Talbot
        <[email protected] <mailto:[email protected]> <mailto:[email protected]
        <mailto:[email protected]>>> wrote:

            I add: a pure function can call extern code and diverges,
        so the
            pure requirements are a subset of the CTFE requirements.


        How do you plan to enforce that a function won't diverge?

        Are there any systems which allow calling functions and
        enforce convergence without using dependent types?

        (We could probably enforce it by prohibiting both mutual and
        self-recursion as well as loops, but I'm guessing this would
        be too restrictive to be acceptable.)


            Pierre

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