(C++) Loop: User Input Without Reserving Memory

Question

Is there a way I can have a user input a bunch of integers consecutively, but when she/he is done she/he would press -111 (must be this number) when finished without having to initialize another data type?

Like this:

while(what the user puts in is not -111)

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The integers will be pumped into a vector of integers as the user types them in, and I don't want -111 in the vector. Perhaps it should instead be a do-while loop. — Loie Benedicte, Aug 02 '13 at 00:44
@TomásBadan I'm not sure if that's what the OP is asking. I think he/she is just looking at the much simpler problem of reading until some specific number is given. It would be nice if the OP could clarify this. — Zong, Aug 02 '13 at 00:55
@ZongZhengLi Maybe you are right. I had understood (s)he wants to read the input buffer in an unbuffered mode. Maybe it is a simpler question. — Amadeus, Aug 02 '13 at 01:06

score 2 · Answer 1 · answered Aug 02 '13 at 01:19

2

How about this

  int i;   
  do {
    std::cin >> i;
  } while (i != -111);

answered Aug 02 '13 at 01:19

skuzniar

121
4

score 2 · Answer 2 · answered Aug 02 '13 at 05:41

2

This is extremely simple. But the other answer doesn't even handle end of input, so this is better

int i;
while (cin >> i && i != -111) {
    ...
}

answered Aug 02 '13 at 05:41

Zong

6,160
5
32
46

What exactly is better? The other answer handles the end of input correctly. In fact, it's more robust than your's - you rely on operator precedence and order of evaluation to get the result (either intentional or not) - that's can be broken easily and you end up with unexpected behavior due to usage of uninitialized variable – SomeWittyUsername Aug 02 '13 at 06:00
@icepack: The other answer doesn't handle end-of-file or malformed input. The order of evaluation in this code is well defined, `i` won't be tested unless `cin` was able to read an integer value. – Blastfurnace Aug 02 '13 at 06:10

(C++) Loop: User Input Without Reserving Memory

2 Answers2