Using alias in C++ without altering value of original variable?

Question

So I have to make a program where I calculate the sum of some elements in an array and then find the number of digits of the sum (e.g. if the sum of several elements is 175, I have to print the value of the sum (175) and the number of digits of 175 (3)).

To determine the number of digits I use the following "while" loop:

while (sum > 0)
{
    sum /= 10;
    digits++;
}

As you might have noticed, at the end of the loop the sum is 0. So I thought of creating an alias of "sum":

int& rSum = sum;

So I simply substituted "sum" with "rSum" in the array, in order to find the numbers of digits, and printed sum in the end of the program. Anyways, the value of "sum" after the loop is 0, in other words equal to "rSum". So I guess, when you create an alias to a certain variable, modifying the alias, modifies the variable itself, which is a problem in my case.

My question is, can I create the program with aliases (or using references, pointers etc.), or is the only way by creating a copy of the "sum" variable (int rSum = sum;)?

score 3 · Accepted Answer · answered Nov 15 '14 at 15:15

Your question looks like "how can I make a copy this variable without making a copy of this variable?".

I think your concern roots one level lower, you think making a copy would make the code less readable - and I agree. But you can combat it very simply:

int sum = ...;
int digits = countDigits(sum);

Extracting countDigits to a separate function will still make a copy of your sum variable, since it's copied by value (which is OK), but this copy will be temporary (local to countDigits) and won't make an unneccessary mess in your original function.

The real reason I'm trying to do this is because I'm learning about pointers and references in college so I wanna find different (and supposedly better) ways of executing certain tasks using this stuff. I simply wanna find as many practical applications of the stuff I learn as possible. :) — Boyan Kushlev, Nov 15 '14 at 15:39

score 0 · Answer 2 · edited May 23 '17 at 12:27

0

Skizz proposes here a logarithm based method: Efficient way to determine number of digits in an integer. Or look at Brad's solution. However, if you use division you will need a copy.

edited May 23 '17 at 12:27

Community

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1

answered Nov 15 '14 at 15:14

robert

3,539
3
35
56

score 0 · Answer 3 · answered Nov 15 '14 at 15:32

0

This will also create copy of sum but at least it wont be you:

const int& orgSum = sum + 0;

while (sum > 0)
{
    sum /= 10;
    digits++;
}

cout << orgSum << endl;

answered Nov 15 '14 at 15:32

rockoder

747
11
23

Using alias in C++ without altering value of original variable?

3 Answers3