[colejohnson66]

Theoretically, any language can be interpreted.

Compilation is just interpreting what a program does and producing machine code (or other code in the case of transpilers) that computes the same thing.

Interpreters are just that, but instead of producing code, they run code in themselves thats computes the results directly.

One could even consider machine code just “obfuscated” assembly code. In that sense, machine code is just another language that also could be interpreted (intepretation-based emulators like Bochs) or compiled again (JIT-based emulators like DOSBox).

This brings up a slightly related question: is there a language that can’t be compiled?

[smabie]

Of course not, just compile your interpreter but instead of reading input from a file, have it read input from a fixed string (the source code) that is embedded in the binary. You've just created a super shitty compiler!

[colejohnson66]

I personally wouldn’t consider that a compiler but just an interpreter bundled with the source. For example: Electron based desktop programs aren’t considered compiled (by anyone I know) even though they pack the interpreter (Chromium) with the source.

[chrisseaton]

> This brings up a slightly related question: is there a language that can’t be compiled?

Not sure if you're asking this platonically, but Futamura shows us that if you can built an interpreter then you can always transform that automatically to be a compiler.

This is used in practice by some compilers today - they automatically produce a compiler from an interpreter!

[tyingq]

"question: is there a language that can’t be compiled?"

There is some question whether Perl could be, because parsing it without running it has some ambiguity. https://www.perlmonks.org/?node_id=663393

[viraptor]

That's not really a barrier. It's "can't be parsed without ambiguity", not "can't be parsed". You compile cases like that by compiling a check for the relevant condition, then compile the possible versions in the if/else branches. Unless you can prove which case it will be from other code - then you can simplify anyway.

[Kednicma]

By wielding the Futamura projections [0][1][2], any interpreter may be turned into a compiler. Perl is handled as one case. Crucially, the resulting compiler need not be fast; if the interpreter is slow, then the compiler will be slow too (this is a special case of the central meme from [3], "if the N'th Futamura projection has quality Q, then the N+1'th Futamura projection will also have quality Q.")

[0] https://en.wikipedia.org/wiki/Partial_evaluation#Futamura_pr...

[1] http://blog.sigfpe.com/2009/05/three-projections-of-doctor-f...

[2] https://www.gwern.net/docs/cs/2009-gluck.pdf

[3] https://www.itu.dk/people/sestoft/pebook/