Increment a variable in C++ with a void function - c++

Question

I wanted to make one of my code more concise so I wrote this:
while(m <= r)
nums[m] ? nums[m] == 1 ? m++ : swap(nums[m], nums[r--]) : swap(nums[m++], nums[l++]);
But it's not working because 'swap' is a void function but 'm++' returns int. ('right operand to ? is void, but left operand is of type int' error). So I'd like to know how can I replace m++ so it's of type void.
I know that I can create a new void function (for example void increase(int &x){x++;}) but I want to keep my code as an one liner.
The best working variant I made is 'swap(nums[m], nums[m++])', which does nothing to my array, but it looks awful. What other functions can I use?

Answer 1

I wanted to make one of my code more concise
Baking in a number of side effects into a single expression of nested non-parenthesized ternary operators (making use of implicit conversion to bool) does, if anything, make your code more complex, more bug-prone and may hide the fact that the original code should actually have been broken up and re-factored into something simpler.
Why not favour clarity over over-complex brevity? E.g. starting with the straight-forward approach:
while(m <= r) {
if (nums[m] != 0) {
if (nums[m] == 1) {
++m;
}
else {
swap(nums[m], nums[r--]);
}
}
else {
swap(nums[m++], nums[l++]);
}
}
which can be re-factored into:
while(m <= r) {
if (nums[m] != 0) {
if (nums[m] == 1) {
++m;
}
else {
swap(nums[m], nums[r]);
--r;
}
}
else {
swap(nums[m], nums[l]);
++m;
++l;
}
}
which can be re-factored into:
while(m <= r) {
const std::size_t swap_from_idx = m;
std::size_t swap_with_idx = m; // default: no swapping.
if (nums[m] == 1) {
++m;
continue;
}
else if (nums[m] == 0) {
swap_with_idx = l;
++l;
}
else {
swap_with_idx = r;
--r;
++m;
}
swap(nums[swap_from_idx], nums[swap_with_idx]);
}
or e.g.:
while(m <= r) {
// No swapping.
if (nums[m] == 1) {
++m;
}
// Swapping.
else {
const std::size_t swap_from_idx = m;
std::size_t swap_with_idx = l;
if (nums[m] == 0) {
++l;
}
else {
swap_with_idx = r;
--r;
++m;
}
swap(nums[swap_from_idx], nums[swap_with_idx]);
}
}
At this point you may ask yourself is the original loop design is overly complex, and/or if you should break out part of the loop body into a separate utility function.
If your if/else if/else logic is reaching a too high cyclomatic complexity, the answer is seldom to try to hide it by means of a highly complex tenary operator expression, but rather by re-factoring and, if applicable, breaking out some parts in separate functions.

Answer 2

If you want the expression m++ to have a side-effect, and have a void type, you can simply cast the expression like this:
(void)m++
which will evaluate the m++ first, and then cast it to void.
Here's a demo.