DBASIC

A minimal programming language (and compiler), for learning to write a compiler.

Why?

I wanted to learn how to write some rudimentary compiler. The best way to learn someting is to just do it!

What kind of language is it?

TinyBASIC served as a starting point, as it is such a small language and easy to implement. Over time I added new features and tweaked existing ones. Now it is some independent dialect of BASIC.

What is it good for?

Honestly the practical use of DBASIC is somewhat limited, but I think it is great to learn about compiler design. It helped me a lot to understand the subject and I think it might be of great use for others too. The code is super heavily commented (especially the tricky parts) and should be easy to understand.

The language

Detailed specifications for the language can be found here.
Here is an example for recursively calculationg and printing fibonacci numbers:

FUNC main() INT
    print("How many?:")
    INT dest = input()
    INT x = 0
    WHILE x < dest DO
        print("%d,",fib(x))
        x = x+1
    END
    print("\n")
    RETURN 0
END

FUNC fib(INT n) INT
    IF n < 2 THEN
        RETURN 1
    ELSE
        RETURN fib(n-1)+fib(n-2)
    END
    RETURN 0
END

More examples can be found in the examples folder.

How to use it?

First you need to install the compiler:

pip3 install git+https://github.com/dbaumgarten/dbasic.git

You can also install it in development mode so you can easily modify the compiler.

git clone https://github.com/dbaumgarten/dbasic.git
pip install -e dbasic

You will also need to have GCC installed as it is used to assemble and link the generated assembly code.

Now compile your first programm:

dbc yourfile.basic

This will result in an executable called "yoourfile" in the same directory.
For additional options (outputting c/asm, input-files, output-files etc.) see dbc --help

Limitations

As the language and the compiler needed to stay quite simple there are some limitations:

• INT and BOOL are the only variable types (But calls to print() or C-functions can still use string-constants as arguments)
• Currently no stdlib
• The generated assembly-code is 100% unoptimized.
• Only linux is supported and valid compilation targets are C and x86-64 assembly

Stability guarantees

None. I am still playing around with this, adding and changing features without caring for backwards compatibility. Even significant changes to the language itself may suddenly appear. If you need (for whatever reason) a stable version, just fork the repo.