Passing variables in C++

Just a bit of condensed info that people will hopefully find helpful…

Variables that go ‘in’ but not ‘out’:
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void foo(int x)
{
x=6;
}

-x will not be modified outside the scope of foo
-x is copied (consider overhead for big things)

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void foo(int const &x)
{
x=6; //will no compile
}

-x cannot be modified inside foo
-x is not copied, preventing some overhead

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Variables that go in and out
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void foo(int &x)
{
x=6;
}

-x will be modified within foo and outside of foo
-x is not copied, preventing overhead, but modification of x outside of foo may be undesirable. see the use of const above.
-simpler than using pointer technique and avoids having to change calling code to pass a pointer

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void foo(int *x)
{
*x = 6;
}

-the value at *x will be modified inside and outside foo
-x is not copied
-involves more effort to program

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