Rover Lang

Language created for the 2022 Unofficial Lang Jam by matan1905.

The theme of the lang jam was: it's not a bug, it's a feature.

About the language

Disclaimer: while this is a working language, it is not meant to be taken seriously. It's a bad idea to use it for any serious application, and this is by design.

We created a language that can be used for programming Mars rovers (or other rovers), and out of the box it handles some of the common problems you could find in such a low-memory environment that needs to deal with accurate measurements. This way, you don't have to worry about these issues, they are handled for you!

Metric-imperial conversions

We know that converting between metric and imperial measurement systems might be problematic. For that reason, any comparison assumes that the left-hand side is in imperial, and the right-hand side in metric. Left-hand side is automatically multiplied by 1.6, so that you don't have to worry about conversions!

Integers

While we suggest using floating-point numbers for most calculations (they come with the measurement conversions built in!), we are aware that sometimes you might need integers, for example to store date. However, in order to lower the memory usage, we thought: what is the largest integer that you might need? We came to a conclusion that the highest integers would be used in date calculations, so we limited the value of an integer to 99. After that, it rolls back over to 0, making those date calculations so much easier!

User-defined functions

We know stack overflows can be a problem in systems where memory is limited, such as a Mars rover. For that reason, we do not allow the programmers to define their own functions. No recursive functions, no risk of a stack overflow!

Syntax

Ok, so how does the code actually look like? The language itself is a simple imperative language, with C-like syntax. You can have a look at the example programs in test_code/. The language supports:

printing stuff using the built-in printf function
variables and constants
conditionals and loops
arrays, with useful built-in functions: length, push and pop

Please note, that:

a variable/constant definition always requires an initial value to be provided
strings can only be used for printing stuff, they cannot be stored in variables or otherwise interacted with (as ASCII characters will not fit into Rover integers)
no breaks, continues or any other type of early return is available

Building and running the interpreter

The interpreter is written using C++17, and you can build it easily using CMake (>= 3.14). We have verified that GCC 9.3.0 and clang 11 successfully build the project, we cannot guarantee that an earlier version of either of these will work.

If you don't know how to use CMake, you can do the following in the project directory:

mkdir build
cd build
cmake ..
cd -
cmake --build build

After that an executable will be present under build/rover. You can run a program by providing a path to the source code as a parameter, e.g.:

rover test_code/simple.🚲

Note: we are using a bicycle emoji as the file extension (because the Polish word for bicycle is the same as the English word for rover). We have not encountered any issues using this extension. However, the interpreter itself does not check for the extension, so if you do run into any issues, you can change it to whatever you want (we recommend .rvr).

Acknowledgements

See contributor list for project authors. Note that the actual contributions might not match the commit authors, since we did some pair/group coding.

mrozycki/rover-lang