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#299 in Command-line interface

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Brim is an optimizing brain* interpreter than nonetheless strives to be very pleasant and easy to use.



Brim supports two types of tape: 30000-long wrapping, or non-wrapping dynamic-width. The former is default; the latter is through feature dynamic_array.

The cells themselves have three features you can customize: wrapping, width, and signedness. By default, cells are unsigned bytes that wrap. However, through combining the following features, you can achieve multiple different kinds of cell: - nowrap: Disables wrapping on increment/decrement - wide_cell: Changes cells to be 64-bit - signed_cell: Changes cells to be signed


If compiled in debug mode, or with the feature flag debug, brim will recognize the character ;. This will dump several relevant bits of info (the tape, the tape pointer, and three instructions for context) to the supplied output.

File I/O

With the -i | --input and -o | --output flags, brim can read/write to/from files instead of stdin/stdout.

Regardless of source or destination, all I/O is buffered to provide a fast and reliable experience (the output is flushed on each newline, and upon exit).


Brim internally uses a token-based intermediary structure to execute the code. First, it groups together add, subtract, left, and right instructions to eliminate repetitive cycles (as well as discard redundant instructions).

Then, it performs several macro-optimizations to reduce common operations to a single "instruction". Currently, it recognizes:

  • Zeroing a cell ([-])
  • Setting a cell to a value ([-]++++)
  • Moving one cell to another ([->+<] / [>+<-])
    • Also recognizes multiplication ([->+++<])
  • Subtracting one cell from another ([->-<])
  • Scanning for a zero cell ([>>>])
  • Duplicating a cell ([->+>+<<])
    • Also recognizes multiplication (as with moving)

The token-based structure makes these trivial to recognize, since repeating instructions have already been collapsed into one.

Finally, it iterates over each bracket ([/]) and pre-loads its destination, so executing them requires zero lookup time (it just overrides the IP).

These are all run in a buffered I/O environment, as detailed above.


This crate is also available as a library. The executable simply provides a CLI interface to the library. The points of interest are the parse and optimize functions, as well as the Token enum.


Brim isn't finished yet! My hopes for the future include:

  • More macro-optimizations
  • Tape customizations via features
  • Cell behavior variants via features


Contributions are always welcome, especially optimizations. Please, before you create a pull request, run cargo fmt and cargo clippy.

If you want to implement a new feature, consider gating it behind a feature flag. This can reduce code size as well as slightly improve runtimes. It isn't appropriate for all additions, but it is worth considering.