[SOLVED] switch statement in implementing an fsm in c

[winnie mong]

hi guys,
i have a question concerning the use of the switch statement.i am wondering if case zero corresponds with state 0 and case1 corresponds with state1.with my code below, i want case 0 to execute,which will then state=1 and for state 1 i want i want case 2 to execute.so i am not sure if thats how thw switch statement works.some body help!!

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Code C - [expand]
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int i,j,state;
void geyser_state_check();
void do_set_time ( const char *const menu2[]);
 
do{
    state=0;
    {
        switch (state){
            case 0:
                geyser_state_check();
                if (mode()){
                    state=1;
                }
                break;
            case 1:
                j=choice(menu1);
                if (menu1[j]=SET TIME){
                    do_set_time();
                break;
                }
                else if(menu1[j]=VIEW TIME){
                    do_view_time(); 
                    break;
                }
                else {
                    state=0;
                    break;
                }
                break;
        }
    }
}while(1);

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[kam1787]

it might depend on the compiler, but if my memory serves it doesn't work that way - it depends on the 'initial' value given to the switch.

is this what you want within the DO loop?

geyser_state_check();
if (mode())
  { j=choice(menu1);
    if (menu1[j]=SET TIME){do_set_time();}
    else if(menu1[j]=VIEW TIME){do_view_time(); 
  }

 

[milan.rajik]

i want case 0 to execute,which will then state=1 and for state 1 i want i want case 2 to execute

I really didn't understand what you are asking.

According to your code case 0 is executed when start is 0, case 1 when state is 1,


If you want case 0 to execute when state is 1 and case 2 to execute when state is 2.

then change code to

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Code C - [expand]
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switch(state + 1) or

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change case 0 to case 1 and case 1 to case 2.


If you want case 0 to execute when state is 1 and then case 1 to execute when state is 1 then

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Code C - [expand]
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switch(case)
 
    case 0:
 
    case 1:
 
        break;

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Your expalnation is not clear. If you need a better answer then explain what you want clearly.

 

[FvM]

The switch statement evaluates the value of variable state and jumps to the respective case. As state is set to 0 in the line before, only case 0 will be ever executed.

 

[Ricardo_Electropepper]

It will probably work better if you erase line 6, otherwise it will always do case 0.

 

[winnie mong]

oh there was a mistake, yes what i want is for it to do case 0 when in state 0, and case 1 after updating state=1.i want the whole code to be executing infinitely.

 

[milan.rajik]

Try this

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Code C - [expand]
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//value of state change elsewhere in while(1) loop or ISR.
 
while(1) {
        
    
        switch (state) {
                    
        case 0:
                    //code to execute when state is 0
                    break;
                case 1:
                    //code to execute when state is 1
                    break;                
                    
        };      
 
}

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[winnie mong]

i tried to do like you advised, it makes sense now.thanks

while(1) {
		switch (state)
		{
			case 0:
				geyser_state_check();
				if (mode()){
					state=1;
				}
				break;
			case 1:
				j=choice(menu1);
				if (menu1[j]=SET TIME){
					do_set_time();
				break;
				}
				else if(menu1[j]=VIEW TIME){
					do_view_time();	
					break;
				}
				else {
					state=0;
					break;
				}
				break;
		};
	
}

- - - Updated - - -

is it ok that i have case 0, taking me to case 1 through the statement "state=1"?because for case 1 to execute, mode button has to have been pressed.

 

[milan.rajik]

You don't need the break; statement in else { } block.

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Code C - [expand]
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else {
    state=0;    
}
break;

---

 

[winnie mong]

is it ok that i have case 0, taking me to case 1 through the statement "state=1"?because for case 1 to execute, mode button has to have been pressed.

- - - Updated - - -

oh, i removed the break there and i have an error saying that same else is inappropriate.
what could be the problem?

 

[milan.rajik]

If state has to be 0 before pressing mode button then it is correct. switch statements work like this... if case is 0 then code related to case 0 is executed and then switch exits even if mode was pressed and state was changed to 1. In the next while(1) loop case 1 code executes as state was set to 1 previously.

 

[winnie mong]

wow, this is so help full.thanx a lot.
atleast i have move a step forward with my project.