How to have an if() split by && and not || - c++

Question

I'm trying to do something like this in c++
If x is equal to either a or b or c
and y is equal to either d or e or f
and z is equal to either g or h or i, it would turn true and execute the code
I am a bit lost in this
if(x==a||x==b||x==c && y==d||y==e||y==f && z==g||z==h||z==i){
// Do x
}

Answer 1

Just use && and ||, with parentheses to make the grouping clear.
if ((x == 'a' || x == 'b' || x == 'c')
&& (y == 'd' || y == 'e' || y == 'f')
&& (z == 'g' || z == 'h' || z == 'i')) {
// execute code
}

Answer 2

If you look at C++ operator precedence you'll find that && has higher precedence than ||.
That means that your if statement
if(x==a||x==b||x==c && y==d||y==e||y==f && z==g||z==h||z==i)
is the same as
if (x == a || x == b || (x == c && y == d) ||
y == e || (y == f && z == g) ||
z == h || z == i)
By using parentheses, you can change it to work the way you want:
if ((x == a || x == b || x == c) &&
(y == d || y == e || y == f) &&
(z == g || z == h || z == i))

Answer 3

It is a straightforward translation from what you said to C++ code:
if ((x == a || x == b || x == c) &&
(y == d || y == e || y == f) &&
(z == g || z == h || z == i))
{
}
Most real programs don't have conditionals this complex. Split up your logic into logical tests.

Answer 4

From the previous answers, the important point is that in C++, you missed that the AND operator && has a higher operator precendence than the OR operator ||.
This can be compared to how the multiplicative operators *, /, % of numbers have higher precedence than additive operators + and - in algebra.
Regroup the parathetheses so you have these three requirements of what x, y, and z have to be, and the statement is true when all three are correct. (Technically, this is called a product of sums form, as the if statement requires the truth of all three smaller statements (the AND), where each of the smaller statement uses only OR statements.).
if((x==a||x==b||x==c) && (y==d||y==e||y==f) && (z==g||z==h||z==i)){
// Do x
}
Your original code would be equivalent to
if(x==a || x==b || (x==c && y==d) || y==e || (y==f && z==g) || z==h || z==i){
// Do x
}
For larger if-statements, you can also use newlines but of course that will take up more lines.
if((x==a||x==b||x==c)
&& (y==d||y==e||y==f)
&& (z==g||z==h||z==i)
&& ... other conditions)){
// Do x
}
If you do not want such cumbersome and long if-statement notation, you can consider breaking into logical tests (the if-condition is the "product" of the logical tests), namely
bool a1 = (x==a||x==b||x==c);
bool a2 = (y==d||y==e||y==f);
bool a3 = (z==g||z==h||z==i);
bool a4 ...
if (a1 && a2 && a3 && a4 && ..) {
// Do x
}

Answer 5

Try using parentheses to separate your questions:
if( (condA || condB || condC) && (condD || condE || condF) && (...)) and so on.
(condA = condition A)

Answer 6

Going a little overboard here (but just a bit):
if (element_of(x, {a, b, c}
&& element_of(y, {d, e, f})
&& element_of(z, {g, h, i}))
{
foo();
}
with element_of defined as:
template <class T>
auto element_of(const T& element, std::initializer_list<T> list) -> bool
{
return std::find(list.begin(), list.end(), element) != list.end();
}
Or a even a little bit more overboard (this is just for fun, I don't recommend it):
if (Elem{x}.element_of({a, b, c})
&& Elem{y}.element_of({d, e, f})
&& Elem{z}.element_of({g, h, i}))
{
foo();
}
with Elem:
template <class T> struct Elem
{
T element;
auto element_of(std::initializer_list<T> list) -> bool
{
return std::find(list.begin(), list.end(), element) != list.end();
}
};
template <class T> Elem(T) -> Elem<T>;