It is a bit more complicated. Sbcl, as an example, does check types on defun statements. Some it will just warn about, but some will prevent the completion.

It was so not about comparing, but learning c/c++ is often a less fun experience due to either the write / compile / debug cycle or the heavy tooling required.

A c/cpp repl would make people fiddle around and have a rapid intuition. Then they go without.

I don't think monkey patching is required. Although without a dedicated interpreter, you can just do what sbcl does under the hood and maintain what is essentially a tempfile and keep compiling that and reporting the output for every new line/block of code. (I don't know how sbcl actually works, being a lisp I presume it doesn't actually use a tempfile but instead a list in memory of the code the user submitted and then invokes the compiler as needed for new input including the output state as available symbols.)

A cycle that went something like:

    1. Write the line to a file
    2. Compile file with default flags
    3. Run binary in gdb causing gdb to dump certain interest info (stack info, variable contents, etc)
    4. Read the sections/symbols and merge this data into the gdb data (maybe get it from gdb)
    5. Dump this data into your reply and refresh waiting for user input.

You could have a few basic commands in the repl:

Modify the compiler args Add/remove/edit a line Attach gdb.

Emacs or vim could easily do this, and I suspect there are people who already do almost exactly this.

You could also just use any editor/ide with debug integration and keep a scratch file around...

Julia is kind of nice example of what’s possible with dynamic language and static types.

Such REPLs exist since XDE for Mesa in Xerox PARC, and there are some for C++, C#, F#, OCaml, Haskell, Java, among others.