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Comment by zozbot234 | Hacker News Reader

I'm a bit skeptical about the "fantastic interop" with C++ also. If it was that easy, the Rust folks would have done that already; whereas it seems that they're still looking into it. And Rust is being developed for LLVM, a compiler that's also shared with C++.

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With `nim cpp` the Nim compiler actually just generates C++ from the Nim source for the backend to compile. So, calling C++ code is just emitting the calls at a C++ source level and so is straightforward. The situation with Rust "sharing" LLVM is very different, as that is not a source-to-source compiler.

C++ code calling Nim code is also not usually as straightforward. So, "fantastic" here may apply only in one call direction.

The way to enable C++ code calling Nim is via exportc or exportcpp and by writing a head file with the declarations you are exporting

This will require manual work, but you can use macros or a code generation script to help if your api is large.

Rust doesn't have an option to generate C++ code; Nim does.

> Rust is being developed for LLVM, a compiler that's also shared with C++.

Not at all relevant (and LLVM is a backend target, not a compiler).

Rust cbindgen has an option to generate C code, which is generally also valid C++.

Also not relevant since it lacks Nim's mechanisms for integrating the generated code with user-provided C++. You said that you questioned Nim's "fantastic interop" but you have no valid logical reason to ... certainly Rust not having it isn't any sort of argument.

> (and LLVM is a backend target, not a compiler).

LLVM is a backend compiler which compiles to backend targets like x86, which have their own compilers. It's hard to say exactly what a compiler is and isn't, because it's compilers all the way down; compilers are made of compilers.

My working definition is a compiler is a program that turns code from one form into another, whether that's machine code, byte code, IR, or some other high level source. It's a broad definition but it covers all the things we call "compilers".

So you have an idiosyncratic definition of compiler that no one else uses.

https://en.wikipedia.org/wiki/Compiler

"In computing, a compiler is software that translates computer code written in one programming language (the source language) into another language (the target language)."

https://en.wikipedia.org/wiki/LLVM

"LLVM, also called LLVM Core, is a target-independent optimizer and code generator.[5] It can be used to develop a frontend for any programming language and a backend for any instruction set architecture. LLVM is designed around a language-independent intermediate representation (IR) that serves as a portable, high-level assembly language that can be optimized with a variety of transformations over multiple passes.[6]""

As I correctly said, LLVM is not a compiler, it is a backend target of Rust, C++, etc. compilers. They read source language and generate backend output ... anything from assembly language to C++. Even when Nim uses the C++ backend, C++ is the backend target, even though the generated C++ is fed to a C++ compiler.

End of story and of my participation.

> So you have an idiosyncratic definition of compiler that no one else uses.

My definition is supported by your links, so I don't think it's idiosyncratic at all.

> "In computing, a compiler is software that translates computer code written in one programming language (the source language) into another language (the target language)."

That's exactly what I said:

"My working definition is a compiler is a program that turns code from one form into another"

> LLVM... is a target-independent optimizer and code generator.

Code generators are a kind of compiler. The input language is IR, and the output language is machine code. Thus it fits the definition of a compiler you proffered.

> As I correctly said, LLVM is not a compiler, it is a backend target of Rust, C++, etc. compilers.

These things are not mutually exclusive. It can be a target of Rust, C++, etc., but that doesn't make it not a compiler. LLVM being a compiler is supported by both of your wiki links. Your first link lists LLVM under "Notable Compilers and Toolchains". In the second link in the LLVM infobox it reads "Type: Compiler". Nuff said.

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