[gnulinux]

That's not necessarily the only approach though. In a dependently typed language like Agda, there is also no difference between compile-time or runtime computation, not because things can change any time (Agda is compiled to machine code and is purely functional) but because types are first-class citizens, so any compute you expect to be able to run at runtime, you can run at compile time. Of course, this is in practice very problematic since you can make compiler infinitely loop, so Agda deals with that by automatically proving each program will halt (i.e. it's Turing-incomplete). If it's not possible to prove, Agda will reject to compile, or alternatively programmer can use a pragma to force it (in which case programmer can make the compiler run infinitely).

[kazinator]

Why obsess over the compiler running into a loop? That's way less harmful than the compiled application getting into a loop on the end user's machine.

[noelwelsh]

I think part of the purpose of the Agda project is to see how far they can push programs as proofs, which in turn means they care a lot about termination. A language that was aimed more at industrial development would not have this restriction.

[kazinator]

If you want to prove propositions at compile time, isn't it hampering not to have Turing-complete power?

[gnulinux]

No it's not, you can write an extremely large set of programs in non-Turing complete languages. I personally consider Turing completeness a bug, not a feature, it simply means "I cannot prove the halting problem of this language" which blocks tons of useful properties.

You can write useful programs in Agda. I wrote all kinds of programs in Agda including parsers and compilers.