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Most interpreters (not all, but most) are actually a compiler and a VM, yes. The difference between a "compiler" and an "interpreter", in practise, seems to be that "compilers" lack a built-in interpreter.



Most static language compilers include an interpreter for constant expressions at a minimum, because otherwise statically allocating things like arrays is a bit tricky. Handily, this interpreter can be reused for constant folding.

C++ compilers nowadays necessarily include a Turing complete interpreter.


C has one in the preprocessor, to do platform-independent conditionals.


That's another very good point. One can just as well think of the VisualWorks Smalltalk VM as a compiler (which is actually implemented in Smalltalk) with an interpreter+JIT which also functions as a linker. This means, one can also think of Smalltalk as a compiled language with lots of late binding that makes for a more complicated linker. (JIT) Then the part that's a byte code interpreter can be thought of as an "optimization" on the compiler+linker combination. In fact, if you don't want to bother with flexible debugging, you could implement Smalltalk as a compiled language with "fancy linking" and no interpretation at all.

Any interpreter vs. VM distinction is mostly a social construct. Looked at technically, it's a mishmash.


Also, a linker is very similar to a simple garbage collector: it follows code references, marking blocks as it goes (physically allocated in the final output), and adding the references in those blocks to its current list of references to resolve, until it runs out of references to resolve (done) or fails to resolve a reference (link error). All the references then need to be patched up according to their final address, very similar to a GC fixing up memory references.




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