Switch statement c++ - c++

Question

I am writing a code to assign a scoring system to values of a card. I have a member function that takes an int and changes its value based on the scoring system. I can't seem to get it to output anything besides 10 :
int Obj::eval(int b)
{
switch (b)
{
case 0:
b = 11; //automatically assigns ace value of 11
case 1:
b = 2;
case 2:
b = 3;
case 3:
b = 4;
case 4:
b = 5;
case 5:
b = 6;
case 6:
b = 7;
case 7:
b = 8;
case 8:
b = 9;
case 9:
b = 10;
case 10:
b = 10;
case 11:
b = 10;
case 12:
b = 10;
}
return b;
}

Answer 1

Insert break at the end of each case. C's switch is "fall-through": if you don't prevent it, code just keeps executing next line: if b is 0, all the assignments will get executed, in order. break will jump out of the switch.
I.e. your code needs to look like this:
switch (b)
{
case 0:
b = 11; //automatically assigns ace value of 11
break;
case 1:
b = 2;
break;
/* ... */

Answer 2

A switch case should end with a break;. Otherwise there will be a fall through and all the subsequent cases will be executed.
Your code should look something similar to this.
switch(b)
{
case 0:
//bodyhere
break;
case 1:
//bodyhere
break;
}
It's important not to miss the break statements unless you intend to execute the following cases too.

Answer 3

You should always use the break statement after each case because C++ will continue to execute the next case. For example:
switch(b)
{
case 0:
// body
// body
break;
case 1:
// body
// body
break;
case 2:
// body
// body
break;
}
You can also use a default as a last case. However, you don't need a break statement with the default.
switch(b)
{
case 0:
// body
break;
case 1:
// body
break;
case 2:
// body
break;
default:
// body
}

Answer 4

Switch statements in C and C++ have a "feature" called fallthrough, where if you don't actually break out of the cases, execution will just continue through to the next case (thus always resulting in b receiving 10).
Add break statements after each case.
case 0:
b = 11; //automatically assigns ace value of 11
break;
case 1:
b = 2;
break;
case 2:
b = 3;
break;
// etc.

Answer 5

Languages derived from C where control moves to the matching case, and then execution continues or "falls through" to the statements associated with the next case in the source text. Should use a break to avoid it.
case 0:
b = 11;
break;
case 1:
b = 2;
break;
In your case return would be fine too,
case 0:
b = 11;
return b;
case 1:
b = 2;
return b;

Answer 6

In addition to the case fallthrough problem described above, there are more efficient means other than switch to map between values, such as std::map
static map<int, int> myMap = { { 0, 11 }, { 1, 2 }, { 2, 3 }, ... { 11, 10 }, { 12, 10 } };
int Obj::eval(int b)
{
return myMap[b];
}

Answer 7

You need to add a break statement at the end of each branch. Otherwise the flow of control will continue to the next branch.