5 kyu

My smallest code interpreter (aka Brainf**k)

1,853 of 8,397ssineriz

Description:

Inspired from real-world Brainf**k, we want to create an interpreter of that language which will support the following instructions:

  • > increment the data pointer (to point to the next cell to the right).
  • < decrement the data pointer (to point to the next cell to the left).
  • + increment (increase by one, truncate overflow: 255 + 1 = 0) the byte at the data pointer.
  • - decrement (decrease by one, treat as unsigned byte: 0 - 1 = 255 ) the byte at the data pointer.
  • . output the byte at the data pointer.
  • , accept one byte of input, storing its value in the byte at the data pointer.
  • [ 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.
  • ] 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.

The function will take in input...

  • the program code, a string with the sequence of machine instructions,
  • the program input, a string, possibly empty, that will be interpreted as an array of bytes using each character's ASCII code and will be consumed by the , instruction

... and will return ...

  • the output of the interpreted code (always as a string), produced by the . instruction.

Implementation-specific details for this Kata:

  • Your memory tape should be large enough - the original implementation had 30,000 cells but a few thousand should suffice for this Kata
  • Each cell should hold an unsigned byte with wrapping behavior (i.e. 255 + 1 = 0, 0 - 1 = 255), initialized to 0
  • The memory pointer should initially point to a cell in the tape with a sufficient number (e.g. a few thousand or more) of cells to its right. For convenience, you may want to have it point to the leftmost cell initially
  • You may assume that the , command will never be invoked when the input stream is exhausted
  • Error-handling, e.g. unmatched square brackets and/or memory pointer going past the leftmost cell is not required in this Kata. If you see test cases that require you to perform error-handling then please open an Issue in the Discourse for this Kata (don't forget to state which programming language you are attempting this Kata in).
Interpreters
Algorithms

Stats:

CreatedOct 18, 2013
PublishedOct 18, 2013
Warriors Trained58959
Total Skips20700
Total Code Submissions76839
Total Times Completed8397
JavaScript Completions1853
Python Completions2367
Ruby Completions309
Haskell Completions267
Clojure Completions78
Java Completions806
Crystal Completions14
PHP Completions190
C++ Completions876
TypeScript Completions278
Rust Completions533
C Completions458
BF Completions24
CoffeeScript Completions13
Swift Completions68
C# Completions445
Elixir Completions47
Dart Completions100
Groovy Completions15
Kotlin Completions151
Factor Completions6
COBOL Completions4
Total Stars1959
% of votes with a positive feedback rating94% of 1489
Total "Very Satisfied" Votes1338
Total "Somewhat Satisfied" Votes120
Total "Not Satisfied" Votes31
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