Is there a full REPL for Erlang?

Question

Is there a way to have a full interpreter in Erlang, not just a "shell".

Since it is a dynamic language, not being able to define named functions in the interpreter is a little bit disappointing... I suspect that it is because compilation units (modules) must be explicitly compiled for their execution by the VM, but maybe a REPL acting as a dynamic/recompilable module exist?

Answer 1

Reading from: http://www.chicagolug.org/wiki/Erlang

Erlang provides a REPL (read, eval, print, loop) that allows you to run Erlang code, compile source files and run functions from those newly compiled Erlang source files which can be started after you have installed Erlang with the command erl. When showing use of the REPL instead of a source file the code will look like:

> c(helloworld).
> helloworld:hello_world(). Distinguishable by the '>' before the

commands. If you can't tell, the above commands in the REPL compile our previous hello world program, notice the compile function, c, takes the module name no the source file name, and then runs the exported function hello_world.

You can also load a new compiled module with:

> l(helloworld).

Answer 2

This is related to http://stackoverflow.com/questions/2065990/defining-erlang-functions-in-the-shell

Short answer:

• Use funs

Longer answer:

• http://ulf.wiger.net/weblog/2007/11/20/extending-the-erlang-shell-part-1/
• http://ulf.wiger.net/weblog/2007/11/21/extending-the-erlang-shell-part-2/
• http://erldocs.com/R13B04/stdlib/shell_default.html

Answer 3

F= fun () -> io:format("Hello World~n", []) end.

F().

Answer 4

The short answer is NO, it does fit into the way that Erlang handles code.

The Erlang VM only supports compiled code. The unit of code handling, including compilation, is the module, you load, delete, update and purge modules. So it is not really possible to mix interpreted and compiled functions the same way as you can in lisp. It would be possible to extend the shell to allow defining interpreted functions within it but these would then only be callable from within shell interpreter and not from other modules. It would also be possible to make the shell recompile and reload "shell module" so functions within it could be called from other modules. But this module would then only really exist within that invocation of erlang.

And I honestly don't really see the point as recompiling and reloading code has always been so fast it has not been a problem. It would more be force of habit than convenience.