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I'm wondering how to use the switch statement, and I have a couple questions.
What is the case '': for? as in, how do I set the conditions?
How many cases can I have?
How do I set the conditions?
It's very simple: assuming an integral type Type you can use:
Type i;
switch (i) {
case x:
// ...
break;
case y:
// ...
break;
// ...
default:
// ...
break; // optional
};
where x, y, ... etc. are values convertible to the integral type Type that you want to check for equality in i.
So for example:
int x = 3;
switch (x) {
case 1:
std::cout << '1';
break;
case 2:
std::cout << '2';
break;
case 3:
std::cout << '3';
break;
default: break;
};
would print:
3
For more detailed informations on the switch statement, please visit this page.
How many cases can i have?
As many as you want.
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My code looks like this
enum possible_cases; //assigned somewhere
bool decision; //assigned somewhere
//basically the default action for my possible_cases
int value = 10;
do_something(value);
switch (possible_cases)
{
case 0:
//assume covered by do_something(value)
break;
case 1:
if ( decision )
{
value = get_other_value();
do_something(value);
}
break;
case 2:
value = get_other_value(); //will return same value as in case 1
do_something(value);
break;
}
As you see
it has to run do_something() with one specific value
it might have to run do_something() with other values additionally, and the list of cases might grow, to a point, where having bools is impractical
but overall I am not happy as it is kinda redundant and I think there is a way to do it better.
I would like to stay with enum of cases
Edit:
It seems not clear where the problem is:
I see the call of the same function in 3 places, while I assume I could reduce it to 2 as I know I need to run it only 2 times at max.
It is really more the aesthetic aspect
The redundant part in your code is do_something(value)
So I would suggest you to separate that part of the code
enum possible_cases; //assigned somewhere
bool decision; //assigned somewhere
//basically the default action for my possible_cases
int value = 10;
switch (possible_cases)
{
case 1:
if ( decision )
value = get_other_value();
break;
case 2:
value = get_other_value(); //will return same value as in case 1
break;
}
do_something(value);
By adding extra layer you might do:
std::optional<int>
get_additionnal_value(Epossible_cases possible_cases, bool decision)
{
//basically the default action for my possible_cases
const int value = 10;
switch (possible_cases)
{
default:
case 0: return std::nullopt;
#if 1
case 1: return decision ? get_other_value() : value;
#else
case 1: if (!decision) return value;
[[fallthrough]];
#endif
case 2: return get_other_value(); //will return same value as in case 1
}
}
and then
do_something(10);
if (auto opt_value = get_additionnal_value(possible_cases, decision)) {
do_something(opt_value);
}
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I was trying to do a quiz in C. 5 answers, only one is correct. I'm using the switch. My doubt is on the case you have the number of the correct answer and the consequence of being correct. But on the other hand, I need to make the other 4 wrong. how can I select multiple answers? is it case 1,3,4,5? P.s. There's also the option of being invalid, and i need a string for each case! pontos mean points and p1 is the answer. Thank you
switch (p1) {
case 2 :
correct answer
pontos = pontos + 1;
break;
case 1, 3, 4, 5 :
wrong answer
pontos = pontos - 1;
default :
Invalid answer
pontos = pontos - 1;
}
You can stack up multiple case statements with the same body, like this:
switch (foo) {
case 1:
case 2:
case 3:
case 5: {
printf("Sorry, wrong answer.");
break;
}
case 4: {
printf("You got it right!");
break;
}
}
Or you could just use a default case to catch everything that's not right:
switch (foo) {
case 4: {
printf("You got it right!");
break;
}
default: {
printf("Sorry, wrong answer.");
break;
}
}
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bool condition = true;
string input = "b";
switch (input)
{
case "b":
if (condition)
{
Console.WriteLine("B");
}
default:
Console.WriteLine("Default");
break;
}
C++:
B
Default
you missed a break after case,
bool condition = true;
string input = "a";
switch (input)
{
case "b":
if (condition)
{
Console.WriteLine("B");
}
break; // You missed break;
default:
Console.WriteLine("Default");
break;
}
C# does not allow to execute more than one case which is logically incorrect so prevented by C# compiler.
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How can I keep track of the order in which switch case statements are executed?
For example:
while (some_boundary) {
switch (value) {
case a:
do something;
move to next value;
break;
case b:
do something;
move to next value;
break;
case c:
do something;
move to next value;
break;
}
}
I want to know if the switch was executed abc or bac or cab, etc.
Any idea ? Or will implementing via if/else make more sense ?
You can save a vector at every iteration with the value of the corresponding iteration:
std::vector<int> sequence;
while (some_boundary) {
int temp = computeValue(); // Or however you get your value.
sequence.push_back(temp);
switch (temp) {
case a:
//do something;
break;
case b:
//do something;
break;
case c:
//do something;
break;
}
}
Edit: This is assuming that value is set somewhere between the while and the switch, so you can save it in advance. Other option is to include the push_back instruction in every case, but is more "dirty". Preallocating the vector could save some computation time as well.
Edit2: code modified according the suggestions so that it is ensured that a new value will be computed.
If you just want to know (and not save the results) you could just output the value at each iteration. Try
cout << value << endl;
as the first line within the while loop.
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"Expected Member name or ";" after declaration specifiers" error appear on the top line switch(stuff)
float waveform = getParameter(6);
switch(waveform){
case 1: Sine signalGenerator
break;
case 2: SawWave signalGenerator
break;
case 3: SquareWave signalGenerator
break;
default: Sine signalGenerator
}
Any suggestions on how to sort it would be great! Thanks in advance!
This is the real code:
float waveform = getParameter(6);
switch(waveform)
{ case 1: Sine signalGenerator break;
case 2: SawWave signalGenerator break;
case 3: SquareWave signalGenerator break;
default: Sine signalGenerator
}
what you want is probably this:
int waveform = (int) getParameter(6);
WaveBase* sigGen;
switch(waveform) {
case 1: sigGen = new Sine; break;
case 2: sigGen = new SawWave; break;
case 3: sigGen = new SquareWave; break;
default: sigGen = new Sine;
}
// use sigGen here
delete sigGen;
this assumes that Sine, SawWave and SquareWave have a common base (they should)
and that its destructor is virtual (it should)