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
]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
The function will take in input…
- the program code, a string with the sequence of machine instructions,
- the program input, a string, eventually empty, that will be interpreted as an array of bytes using each character’s ASCII code and will be consumed by the
… and will return …
- the output of the interpreted code (always as a string), produced by the
Implementation-specific details for this challenge:
- Your memory tape should be large enough – the original implementation had 30,000 cells but a few thousand should suffice for this challenge
- 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 challenge.
The solution in Java code
Test cases to validate our solution