Is It Possible To Do The Following In A Switch Statement - C++? - c++

Question

I am a programming student in my second OOP class, and I have a simple question that I have not been able to find the answer to on the internet, if it's out there, I apologize.
My question is this:
Is it possible have Boolean conditions in switch statements?
Example:
switch(userInputtedInt)
{
case >= someNum && <= someOtherNum
break;
// Is this possible?
}

Answer 1

No this is not possible in C++. Switch statements only support integers and characters (they will be replaced by their ASCII values) for matches. If you need a complex boolean condition then you should use an if / else block

Answer 2

As others have said you can't implement this directly as you are trying to do because C++ syntax doesn't allow it. But you can do this:
switch( userInputtedInt )
{
// case 0-3 inclusve
case 0 :
case 1 :
case 2 :
case 3 :
// do something for cases 0, 1, 2 & 3
break;
case 4 :
case 5 :
// do something for cases 4 & 5
break;
}

Answer 3

No, this is usually the purview of the if statement:
if ((userInputtedInt >= someNum) && (userInputtedInt <= someOtherNum)) { ... }
Of course, you can incorporate that into a switch statement:
switch (x) {
case 1:
// handle 1
break;
default:
if ((x >= 2) && (x <= 20)) { ... }
}

Answer 4

It's not possible directly -- a C or C++ switch statement requires that each case is a constant, not a Boolean expression. If you have evenly distributed ranges, you can often get the same effect using integer division though. e.g. if you have inputs from 1 to 100, and want to work with 90-100 as one group, 80-89 as another group, and so on, you can divide your input by 10, and each result will represent a range.

Answer 5

Or you can perhaps do this
switch((userInputtedInt >= someNum) && (userInputtedInt <= someOtherNum))
{
case true:
//do something
break;
case false:
//something else
break;
}
But that's just down-right terrible programming that could be handled with if-else statements.

Answer 6

This isn't possible. The closest you can some, if the values are reasonably close together is
switch(userInputtedInt)
{
case someNum:
case someNum+1:
// ...
case someOtherNum:
break;
}

Answer 7

C++ does not support that.
However, if you are not concerned with writing portable, standard code some compilers support this extended syntax:
switch(userInputtedInt)
{
case someNum...someOtherNum:
break;
}
Those values must be constant.

Answer 8

If you fancy the preprocessor you could write some kind of macro that auto-expands to the number of case statement required. However that would require a lengthly file with pretty much all case statements (ex: #define CASE0 case 0: #define CASE1 case 1: ...)
You shouldn't go there but it's fun to do...for fun! ;)

Answer 9

The standard does not allow for this:
6.4.2 The switch statement [stmt.switch]
[...] Any statement within the switch statement can be labeled with one or more case labels as follows:
case constant-expression :
where the constant-expression shall be an integral constant expression (5.19).

Answer 10

Some C++ compilers still support range notations today, 8 years after this question was originally asked. It surprised me.
I learned Pascal in 2012, Pascal do have range notations.
So it encouraged me to try the similar syntax in C++, then it worked unexpectedly fabulously.
The compiler on my laptop is g++ (GCC) 6.4.0 (from Cygwin project) std=c++17
There is a working example, which I wrote in hurry. repl.it
In addition, the source code is attached as follow:
#include <iostream>
using namespace std;
#define ok(x) cout << "It works in range(" << x << ")" << endl
#define awry cout << "It does\'t work." << endl
int main() {
/*bool a, b, c, d, e, f, g;
switch(true) {
case (a): break; These does not work any more...
case (b and c): break;
}*/
char ch1 = 'b';
switch(ch1) {
case 'a' ... 'f': ok("a..f"); break;
case 'g' ... 'z': ok("g..z"); break;
default: awry;
}
int int1 = 10;
switch(int1) {
case 1 ... 10: ok("1..10"); break;
case 11 ... 20: ok("11..20"); break;
default: awry;
}
return 0;
}