Why CTFE is context-sensitive?

[Tofu Ninja]

On Monday, 27 January 2014 at 21:37:58 UTC, Ola Fosheim Grøstad 
wrote:
> On Monday, 27 January 2014 at 21:12:30 UTC, deadalnix wrote:
>> lolwut ? How do you make the difference between a program that 
>> won't terminate ever and one that will terminate eventually 
>> (say, in several years) ?
>
> 1. The halting problem does not apply to finite resources. The 
> proof is trivial: just record all state. You are in an infinite 
> loop when you revisit a state your program already has been in. 
> The halting problem only applies if you have non-finite storage.
>
> 2. You can set a timeout and use heurististics (and profiling) 
> for what computations you want to try to precompute. Perfectly 
> doable.

I don't think that is quite right, you can have an infinite loop 
without there being any repeated states. Simple example is

for( i = 1; i>0 ; i++) {...}

This will run forever while still never repeating state, assuming 
that i never wraps around. After all you said that we don't have 
finite resources which is the same as saying we have unlimited 
resources.