FAQ: References and Pointers - Pass-By-Reference with Const

Frequently Asked Questions C++ FAQ
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This community-built FAQ covers the “Pass-By-Reference with Const” exercise from the lesson “References and Pointers”.

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FAQs on the exercise Pass-By-Reference with Const

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Is there any difference between “const int &a” and “int const &a” ?
C++ doesn’t seem to report any problems about this.

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https://www.stroustrup.com/bs_faq2.html#constplacement

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ANSWERED IN EDIT

I’m getting different results from the lesson before this compared to this one doing the same thing. Why is the variable not changing? See example below. Is it the way Codecademy has the VM or whatever set up or am I missing something?

#include <iostream> int triple(int &i) { i = i * 3; return i; } int main() { int num = 1; std::cout << triple(num) << "\n"; std::cout << triple(num) << "\n"; std::cout << num << "\n"; }

Outputs:

3
9
9

#include <iostream> int square(int &i) { return i * i; } int main() { int side = 5; std::cout << square(side) << "\n"; std::cout << square(side) << "\n"; std::cout << side << "\n"; }

Outputs:

25
25
5

How come it’s not this output like the less before?

Expected:

25
625
625

EDIT: I figured it out. It’s because in the first lesson you change the value of i (i = i * 3, then return) and in the second lesson you return i without modifying it.

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I guess I’m a bit confused. I generally get what’s going on, but I don’t understand why you’d choose to pass-by-reference with a const &variable instead of just choosing to pass-by-value instead. It seems like they achieve the same thing. Any benefit to choosing one over the other?