[ruuda]

To me the distinction is not important. It is possible to write programs that take too long to execute in non-Turing complete languages, and when a program hangs, you just terminate it. I think what people really want is for their configuration to remain simple, but not being Turing complete does not guarantee that. For RCL I added a limit on the number of evaluation steps, because without it some programs trap the fuzzer.

[dsheets]

We agree. You don’t want universal computation in your configuration. Your “gas” approach is the right one and very weak computationally. I further posit that you don’t even want to offer gas fuelled TC and everyone would be happy with a provably total primitive recursive language fuelled by gas. Why? Accidents happen. I’d rather have my configuration tool tell me statically that some construct isn’t provably terminating than wait to find out later when someone imports my config snippet library and uses it in an unexpected way.