How to use variable this way c++ - c++

Question

Im making a c++ program wherein there are multiple variables for example:
var1, var2, var3, var4;
i want to use it for a for loop like:
for(int x; x<=5; x++){
if(var1==1){cout << "hi";}
}
But instead of typing var1 i want to make it var"x" where x is equal to 1.
I remember from my batch programming days(not exact) i can use this like:
set x=1
echo var%x%
then the output will be var1.

Answer 1

You can do this, using macros, but I really don't think it is a good idea. Why not use arrays instead? With arrays you can reference the index you want, so instead of var1, var2, var3, ... it will be var[0], var[1], var[2], ... Much more C++ like, anyway.
When using arrays, I would even recommend thinking in one of the container classes C++ offers, such as std::vector, or std::array. To have a simple array of integer variables in a vector, simply declare one such as: std::vector<int> intVec, to extract a specific element use the at function, such as intVec.at(0) which will extract the first element. Really use, almost any other approach, than macros.
Having said that, to do it in a macro you would need to make a macro like this:
#define var(x) var##x
var(1) = 2; // resolves to var1 = 2;
Macros are compile time however, so using them in a loop, by passing a variable to it, will not work the way you would expect. So calling int x = 1; var(x) = 2; would not set var1 to 2, but rather attempt to set varx to 2.
The macro solution comes with a number of disadvantages, one is making your less readable, another is making your code more error prone, and lastly, why stir away from the "C++ way"?

Answer 2

You can make use of command line arguments while invoking your program executable.
prog.exe 3 4 1 6
This way your program will receive 5 command line arguments, the first being the program name itself.
The code will look something like this:
int main(int argc, char *argv[]) {
// For the above example, argc = 5
for (int i = 1; i < argc; ++i) {
// make use of argv[i]
}
}
This may not be exactly what you want to do, but confirms to your idea of multiple variables var1 i.e. argv[1]

Answer 3

It is possible to this in many script programming but unfortunately no direct support is available in C++.
Some ways around are use of arrays (if possible) or an array of pointers to actual variables.
int vars[5] = {...};
for(int x = 0; x < 5; x++){
if(var[x]==1){cout << "hi";}
}
or
int var0 = 2, var1 = 42, var2 = 7;
int *const pvars[] = {&var0, &var1, &var2};
for(int x = 0; x < 3; x++) {
if(*(pvars[x]) == 1)
{
cout << "hi";
}
}
or as mentioned in this comment
int var0 = 2, var1 = 42, var2 = 7;
for(auto &var = {var0, var1, var2}) {
if(var == 1)
{
cout << "hi";
}
}