switch statement C++

[kra9853]

I need help rewriting my if-else statements into a switch statement,

//equations for final grade
LGT=(LG1+LG2+LG3+LG4)/40.*.40*100;
MTPG=MTP*.4;
MTEG=(MTE/55.)*.20*100;

 sum=LGT+MTPG+MTEG;
if(sum>95)  //if-else statements, determines final grade
    letter='A';
else if(sum>85)
    letter='B';
else if(sum>75)
      letter='C';
else if(sum>65)  
      letter='D';
else
     letter='F';
 cout<<"final grade is: "<<letter<<endl;

also i need to somehow get my switch statement to notify the user with the following two cases: If their mid-term Grade is a “D”, ‘You are in danger of failing this course. Please see the Professor’ If their mid-term Grade is a “F”, ‘You are in failing this course. Your Advisor has been notified. Please see both your advisor and the Professor’

[Unimportant]

I really don't think what you want here is a switch, it would make sense in the ruby language, but C/C++ switch statements only accept constants:

switch( sum ) {
   case 100:
   case 99:
   // ... // yes you have to write them all
   case 96:
     letter='A';
     break;
   case 95:
   ...
   case 86:
     //
     break;
   default:
     letter='F';
     break;
}

The switch can cascade (note that I didn't break unless I reached a letter), but I think you'll actually get a slower speed than the simple boolean evaluation you are doing.

Good luck!

Edit: I changed my mind.
This switch statement will be faster than your code.
The reason is because a switch uses the constant as an offset to function pointer (linear access time), so no evaluation is done.
I think for any if-else chain of 3 length or greater, a switch will be faster if a switch is possible. (in C/C++ at least)
If that's questionable you'll have to look up the optimization in your native compiler, I have no intention of doing so. Feel free to correct me if you do this and I was wrong though!

[kra9853]

So.. you can't write a switch for the grade D & F alongside the if-else i made? would that be easier?

[Unimportant]

I just did it for you, what do you mean?

Oh, read my edit sorry.

I said the switch would be faster even if it encompassed every case.

letter='F' should be the default case, mind you.

[kra9853]

This is what i mean would this work after my if-else chain?

switch(letter)
 {
	 case 'D':
		 cout<<"You are in danger of failing this course. Please see the Professor\n";
	    break;
	 case 'F':
		 cout<<"You are in failing this course. Your Advisor has been notified. Please see both your advisor and the Professor/n";
		break;
 }

[Unimportant]

Yes.

[kra9853]

okkay yeah I tried it out and it works :) i got another question for ya,
How do use the pow function with variables? i.e.

//equations for problem 9 page 99 part b
cT=(hT)/2;
iT=(base*(hT*hT*hT))/12;
LT=(sT*iT)/(8*cT);

how would i raise "hT" to the 3 power?

[Unimportant]

pow(base,exp);
pow((double)hT,3); // 3rd power