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‎.gitignore‎

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# Scala CLI
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.scala-build/
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.bsp/
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# Metals
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.metals/
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.bloop/
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project/metals.sbt
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# VS Code
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.vscode/
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.history/
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# IntelliJ
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.idea/
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*.iml
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*.ipr
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*.iws
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# Build
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target/
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out/
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# MacOS
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.DS_Store

‎.scalafmt.conf‎

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version = 3.8.4
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runner.dialect = scala3
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maxColumn = 110
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align.preset = most
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newlines.beforeTypeBounds = fold
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newlines.avoidForSimpleOverflow = [tooLong, punct, slc]
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project.git = true
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rewrite.rules = [RedundantBraces, RedundantParens, SortModifiers, Imports]
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rewrite.scala3.convertToNewSyntax = true
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rewrite.scala3.removeOptionalBraces = true
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rewrite.imports.sort = scalastyle
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rewrite.imports.groups = [["javax?\\..*", "scala\\..*"], [".*"], ["dev.meetree\\..*"]]
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rewrite.trailingCommas.style = keep
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docstrings.wrapMaxColumn = 120
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docstrings.forceBlankLineBefore = false

‎LICENSE‎

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MIT License
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Copyright (c) 2025 Dmitri Polchinski
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.

‎README.md‎

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# Brainfuck
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A simple [Brainfuck](https://en.wikipedia.org/wiki/Brainfuck) interpreter implemented in Scala, built primarily for the purpose of trying out [Scala CLI](https://scala-cli.virtuslab.org/).
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## Usage
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### Running the Project
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```bash
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# Run the interpreter
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scala-cli run . -- "program"
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# Run tests
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scala-cli test .
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```
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### Example Programs
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You can find example programs in the `examples/` directory and run them using:
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```bash
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scala-cli run . -- "$(cat path-to-example)"
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```
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All examples are sourced from [wikipedia.org](https://en.wikipedia.org/wiki/Brainfuck#Examples) and [brainfuck.org](https://brainfuck.org/).
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### Commands
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The language consists of eight single-character commands:
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| Command | Description |
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|---------|-------------|
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| `>` | Increment the data pointer by one (to point to the next cell to the right).|
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| `<` | Decrement the data pointer by one (to point to the next cell to the left). |
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| `+` | Increment the byte at the data pointer by one. |
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| `-` | Decrement the byte at the data pointer by one. |
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| `.` | Output the byte at the data pointer. |
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| `,` | Accept one byte of input, storing its value in the byte at the data pointer. |
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| `[` | If the byte at the data pointer is zero, then instead of moving the instruction pointer forward to the next command, jump it forward to the command after the matching `]` command |
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| `]` | If the byte at the data pointer is nonzero, then instead of moving the instruction pointer forward to the next command, jump it back to the command after the matching `[` command. |
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All other characters are ignored and can be used for comments.

‎examples/addition.b‎

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++ Cell c0 = 2
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> +++++ Cell c1 = 5
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[ Start your loops with your cell pointer on the loop counter (c1 in our case)
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< + Add 1 to c0
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> - Subtract 1 from c1
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] End your loops with the cell pointer on the loop counter
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At this point our program has added 5 to 2 leaving 7 in c0 and 0 in c1
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but we cannot output this value to the terminal since it is not ASCII encoded
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To display the ASCII character "7" we must add 48 to the value 7
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We use a loop to compute 48 = 6 * 8
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++++ ++++ c1 = 8 and this will be our loop counter again
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[
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< +++ +++ Add 6 to c0
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> - Subtract 1 from c1
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]
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< . Print out c0 which has the value 55 which translates to "7"!

‎examples/bubblesort.b‎

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[bsort.b -- bubble sort
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(c) 2016 Daniel B. Cristofani
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http://brainfuck.org/]
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>>,[>>,]<<[
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[<<]>>>>[
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<<[>+<<+>-]
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>>[>+<<<<[->]>[<]>>-]
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<<<[[-]>>[>+<-]>>[<<<+>>>-]]
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>>[[<+>-]>>]<
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]<<[>>+<<-]<<
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]>>>>[.>>]
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[This program sorts the bytes of its input by bubble sort.]

‎examples/helloworld.b‎

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[ This program prints "Hello World!" and a newline to the screen; its
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length is 106 active command characters. [It is not the shortest.]
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This loop is an "initial comment loop", a simple way of adding a comment
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to a BF program such that you don't have to worry about any command
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characters. Any ".", ",", "+", "-", "<" and ">" characters are simply
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ignored, the "[" and "]" characters just have to be balanced. This
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loop and the commands it contains are ignored because the current cell
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defaults to a value of 0; the 0 value causes this loop to be skipped.
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]
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++++++++ Set Cell #0 to 8
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[
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>++++ Add 4 to Cell #1; this will always set Cell #1 to 4
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[ as the cell will be cleared by the loop
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>++ Add 2 to Cell #2
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>+++ Add 3 to Cell #3
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>+++ Add 3 to Cell #4
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>+ Add 1 to Cell #5
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<<<<- Decrement the loop counter in Cell #1
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] Loop until Cell #1 is zero; number of iterations is 4
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>+ Add 1 to Cell #2
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>+ Add 1 to Cell #3
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>- Subtract 1 from Cell #4
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>>+ Add 1 to Cell #6
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[<] Move back to the first zero cell you find; this will
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be Cell #1 which was cleared by the previous loop
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<- Decrement the loop Counter in Cell #0
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] Loop until Cell #0 is zero; number of iterations is 8
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The result of this is:
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Cell no : 0 1 2 3 4 5 6
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Contents: 0 0 72 104 88 32 8
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Pointer : ^
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>>. Cell #2 has value 72 which is 'H'
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>---. Subtract 3 from Cell #3 to get 101 which is 'e'
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+++++++..+++. Likewise for 'llo' from Cell #3
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>>. Cell #5 is 32 for the space
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<-. Subtract 1 from Cell #4 for 87 to give a 'W'
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<. Cell #3 was set to 'o' from the end of 'Hello'
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+++.------.--------. Cell #3 for 'rl' and 'd'
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>>+. Add 1 to Cell #5 gives us an exclamation point
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>++. And finally a newline from Cell #6

‎examples/life.b‎

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[life.b -- John Horton Conway's Game of Life
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(c) 2021 Daniel B. Cristofani
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http://brainfuck.org/]
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>>>->+>+++++>(++++++++++)[[>>>+<<<-]>+++++>+>>+[<<+>>>>>+<<<-]<-]>>>>[
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[>>>+>+<<<<-]+++>>+[<+>>>+>+<<<-]>>[>[[>>>+<<<-]<]<<++>+>>>>>>-]<-
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]+++>+>[[-]<+<[>+++++++++++++++++<-]<+]>>[
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[+++++++++.-------->>>]+[-<<<]>>>[>>,----------[>]<]<<[
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<<<[
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>--[<->>+>-<<-]<[[>>>]+>-[+>>+>-]+[<<<]<-]>++>[<+>-]
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>[[>>>]+[<<<]>>>-]+[->>>]<-[++>]>[------<]>+++[<<<]>
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]<
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]>[
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-[+>>+>-]+>>+>>>+>[<<<]>->+>[
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>[->+>+++>>++[>>>]+++<<<++<<<++[>>>]>>>]<<<[>[>>>]+>>>]
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<<<<<<<[<<++<+[-<<<+]->++>>>++>>>++<<<<]<<<+[-<<<+]+>->>->>
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]<<+<<+<<<+<<-[+<+<<-]+<+[
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->+>[-<-<<[<<<]>[>>[>>>]<<+<[<<<]>-]]
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<[<[<[<<<]>+>>[>>>]<<-]<[<<<]]>>>->>>[>>>]+>
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]>+[-<<[-]<]-[
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[>>>]<[<<[<<<]>>>>>+>[>>>]<-]>>>[>[>>>]<<<<+>[<<<]>>-]>
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]<<<<<<[---<-----[-[-[<->>+++<+++++++[-]]]]<+<+]>
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]>>
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]
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[This program simulates the Game of Life cellular automaton.
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It duplicates the interface of the classic program at
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http://www.linusakesson.net/programming/brainfuck/index.php,
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but this program was written from scratch.
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Type e.g. "be" to toggle the fifth cell in the second row, "q" to quit,
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or a bare linefeed to advance one generation.
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Grid wraps toroidally. Board size in parentheses in first line (2-166 work).
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This program is licensed under a Creative Commons Attribution-ShareAlike 4.0
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International License (http://creativecommons.org/licenses/by-sa/4.0/).]

‎examples/rot13.b‎

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-,+[ Read first character and start outer character reading loop
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-[ Skip forward if character is 0
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>>++++[>++++++++<-] Set up divisor (32) for division loop
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(MEMORY LAYOUT: dividend copy remainder divisor quotient zero zero)
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<+<-[ Set up dividend (x minus 1) and enter division loop
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>+>+>-[>>>] Increase copy and remainder / reduce divisor / Normal case: skip forward
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<[[>+<-]>>+>] Special case: move remainder back to divisor and increase quotient
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<<<<<- Decrement dividend
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] End division loop
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]>>>[-]+ End skip loop; zero former divisor and reuse space for a flag
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>--[-[<->+++[-]]]<[ Zero that flag unless quotient was 2 or 3; zero quotient; check flag
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++++++++++++<[ If flag then set up divisor (13) for second division loop
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(MEMORY LAYOUT: zero copy dividend divisor remainder quotient zero zero)
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>-[>+>>] Reduce divisor; Normal case: increase remainder
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>[+[<+>-]>+>>] Special case: increase remainder / move it back to divisor / increase quotient
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<<<<<- Decrease dividend
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] End division loop
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>>[<+>-] Add remainder back to divisor to get a useful 13
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>[ Skip forward if quotient was 0
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-[ Decrement quotient and skip forward if quotient was 1
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-<<[-]>> Zero quotient and divisor if quotient was 2
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]<<[<<->>-]>> Zero divisor and subtract 13 from copy if quotient was 1
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]<<[<<+>>-] Zero divisor and add 13 to copy if quotient was 0
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] End outer skip loop (jump to here if ((character minus 1)/32) was not 2 or 3)
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<[-] Clear remainder from first division if second division was skipped
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<.[-] Output ROT13ed character from copy and clear it
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<-,+ Read next character
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] End character reading loop

‎project.scala‎

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//> using scala "3.3.5"
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//> using jvm 17
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//> using options -Wunused:imports,implicits,privates -Werror
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//> using option -Ykind-projector
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//> using dep org.typelevel::cats-core:2.13.0
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//> using test.dep org.scalatest::scalatest:3.2.19
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package dev.meetree.brainfuck
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import scala.util.CommandLineParser
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import scala.util.chaining.*
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import dev.meetree.brainfuck.core.Program
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import dev.meetree.brainfuck.interpreter.Interpreter
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import dev.meetree.brainfuck.parser.Parser
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given CommandLineParser.FromString[Program] = Parser.parseOrThrow(_)
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@main def run(program: Program): ExitCode = Interpreter.id
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.interpret(program)
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.fold(err => err.tap(onError).pipe(_ => ExitCode.Failure(1)), _ => ExitCode.Success)
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private def onError(err: Throwable) = System.err.println(err.getMessage)
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enum ExitCode(code: Int):
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case Success extends ExitCode(0)
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case Failure(code: Int) extends ExitCode(code)

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