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esolang/languages/befunge93/README.md
Nilay Majorwar 41b553737a Add developer notes to the language README files
2022-02-18 20:50:53 +05:30

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Befunge-93

Befunge-93 is a two-dimensional esolang created by Chris Pressey, with the goal of being as difficult to compile as possible. The program is a finite 2D grid of operations, and execution can proceed in any of the four main directions. This makes watching the execution of a Befunge-93 program particularly satisfying.

Memory in Befunge-93 is a stack of integers. In addition, Befunge-93 programs can be self-modifying - there are operations that allow accessing and editing the content of the source code at runtime. This means you can also store runtime data in the source code itself, if space permits.

The esolang wiki page contains the complete language-specification, along with some interesting sample programs.

Notes for the user

  • The program grid is padded with space to size 80x25 before execution.
  • Interactive input is not supported in Esolang Park, so currently division-by-zero throws a runtime error.
  • g and p calls that access coordinates outside of the 80x25 grid result in a runtime error.
  • Due to being two-dimensional, the breakpoint functionality is rather uncomfortable to use in Befunge-93.

Implementation details

  • To avoid long no-op stretches, the engine keeps track of the bounds of the user's source code. If the pointer reaches the end of the set portion of a horizontal line, it immediately loops over to the opposite end of the line. The same happens in vertical lines. Try executing >>>> to visualise this.

    Note that this does not happen in string mode. In string mode the pointer loops over the full grid, pushing (space) characters onto the stack.

Possible improvements

  • There seems to be some minor issue in the initial grid padding. Some lines get padded to 81 characters instead of 80. This is only cosmetic though - the program executes correctly.