reple

"Replay-based" REPLs for compiled languages.

reple provides an "interpreter" (REPL) for compiled languages. Each time you enter a line of code, reple will add the new code to your program, compile and run the new iteration of your program, and then print any new output. reple currently supports C, C++, Go, Rust, UPC, MPI, DASH, and BCL.

Installation

Just install the reple pip package.

[xiii@reple ~]$ pip3 install reple
[xiii@reple ~]$ reple -env cxx
> printf("Hello, World!\n");
Hello, World!

If you install the package locally, you might need to add ~/.local/bin to your path.

Usage

To start an interactive REPL session, call reple with the title of a configuration file defined in the /configs directory.

[xiii@reple xiii]$ reple -env cxx
> printf("Hello, World!\n");
Hello, World!
> int x = 12;
> int y = x + 2;
> std::cout << y << std::endl;
14

Functions and Global Variables

To define a new function or global variable, surround your expression with $.

> $void foo() {
  printf("Hello, World!\n");
}$
> foo();
Hello, World!

Errors

reple automatically detects compilation errors, printing them out for you without trashing your REPL state.

> int x = ;                                                                                         
/tmp/repl/repl0.cpp:8:9: error: expected expression
int x = ;
        ^
1 error generated.
>

Multi-Line Statements

It also automatically detects most multi-line expressions, like if statements.

> int x = 12;
> if (x == 12) {
>   printf("Hello, World!\n");
> }
Hello, World!

Runtime Options

Some more complicated runtimes have optional runtime flags. An example of this is the number of processes to run a program with in MPI.

[xiii@reple home]$ reple -env mpicxx --rargs "-n 8"
> int rank, nprocs;
> MPI_Comm_rank(MPI_COMM_WORLD, &rank);
> MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
> printf("Hello, world! I'm %d/%d\n", rank, nprocs);
Hello, world! I'm 0/8
Hello, world! I'm 1/8
Hello, world! I'm 2/8
Hello, world! I'm 4/8
Hello, world! I'm 6/8
Hello, world! I'm 3/8
Hello, world! I'm 5/8
Hello, world! I'm 7/8
>

Adding New Languages

Adding a new language to reple is easy. All you need to do is write a short JSON file that describes (1) how to append REPL lines to form a program, (2) how to compile and run a program, and (3) terminal options, which are things like characters that enclose expressions that can span multiple lines (like {} in C). These config files are typically only about 20 lines, and you can find examples in /reple/configs.

Issues and Contributions

We've tested reple on MacOS, FreeBSD, and a few Linux distros. If you run into any issues installing or using reple, please make an issue using our GitHub repo.

We welcome contributions in the form of pull requests, particularly if you'd like to add support for a new language or runtime system.

xlauko / reple