[luizfelberti]

Feels like the complete opposite s-expressions which are the easiest possible thing to parse, this sounds like a complete nightmare to write a parser for.

It might even be easier to treat the input string as a 2D grid than as a sequence and have a parsing head that behaves like a 2x2 convolutional kernel...

This would make for either a great Advent of Code, or a nightmare interview question, I love it.

[tearflake]

Actually it's quite simple. We parse from left to right. When we hit EOL, we return to the beginning of line and increase Y by one.

Blocks are parsed in the following way: when we get the beginning count of block opening characters, we move Y by one, loop right while whitespace, until we encounter ending count of block characters.

In transposed block, we just switch X and Y, it is easily done with pointers, and use the same code.

[phoe-krk]

    (fst-atom """   trd-atom frt-atom
      """     00001
      asdf    00002 """    fth-atom)
      qwer    00003 hahaha
      zxcv      """ hehehe
      """           hohoho
                    """

I'm not sure I'd like the above to be parseable.