How to get a large integer as input and store it in memory

Question

I know that performing arithmetic on large integers in brainfuck, while perhaps quite tedious at times, is entirely possible.

However what I'm wondering about is what the generally acceptd best-practices are for taking in large integers (or even strings, I suppose) as input.

Most compilers/interpreters allow you to provide full strings at once as input (and then each character is read in individually with a ,). But what I'm wondering is this - how can you read one in if you don't know when the input stream is going to stop? I suppose one way is to tell the user to append a certain character/string of characters to their number to indicate that it's over, but that seems a bit non-user-friendly.

I'd prefer an answer that keeps portability in mind (implementation-specific solutions are of interest, but are not the primary focus of this question). If there is no completely implementation-agnostic way to do this, one that will work on most implementations and fail gracefully otherwise would be the next best thing.

Thanks in advance.

you're writing brainfuck code and are concerned about user-friendliness?? — msw, Jun 24 '10 at 19:23
Wouldn't enter be a reasonable char to identify the end of input? — Mau, Jun 24 '10 at 19:29
@Mau: That's a good idea. Not sure why that never came to mind. What about this? http://en.wikipedia.org/wiki/Brainfuck#End-of-file_behavior ...just came accross that. I'm looking at the part that says you should set the cell to 0 before taking in input, and that if the cell is still 0, that means end of input on most implementations. Does that seem like a good way to go about this? — Cam, Jun 24 '10 at 19:41
@incrediman: Umm, EOF in console input is less user-friendly because it requires the user to press Ctrl-Z or Ctrl-D. — Mau, Jun 24 '10 at 20:13
@Mau yeah, nvm. I think you're right; newline's probably the best way to go about this. Thanks! — Cam, Jun 24 '10 at 20:41

score 2 · Accepted Answer · answered Jun 24 '10 at 20:13

2

Most languages let you read a line from input (e.g. gets() in C, ReadLine() in C# etc). Why not ask the user to enter each value as a line (i.e. separated by enter)?

answered Jun 24 '10 at 20:13

Mau

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score 0 · Answer 2 · edited May 23 '17 at 10:25

Actually I had posted the same code for a different question for a different purpose. Here following code will keep on accepting the ASCII of whatever you type unless a newline character is met.Then prints what you typed.

Don't worry about the portability; I've already implemented addition of two n-digit numbers with this strategy of reading numbers, you can find here.

> +
[ - >,>+< 
  ----- -----    ; minus 10
  [              ; if enters means it is not a \n
    +++++ +++++  ; restore prev value
    < 
  ] >>           ; moving forward
]
                 ; numbers are 0 0 49 0 50 0 51
                 ; for input 123
<<<<[<<]         ; moving to the beginning
>>               ; reaching first char
[.>>]            ; just printing till end

How to get a large integer as input and store it in memory

2 Answers2