Question 16 of assignment 2

Question 16 of assignment 2 uses algorithm 8.3 from F&M, however I cannot see the logic in this algorithm. Can somebody please enlighten me?
The algorithm states:
1.) If the score is smaller or equal to 100, or bigger or equal to 90, then grade = A (which makes sense)
2.) If the score is smaller or equal to 80, or bigger or equal to 89, then grade = B (which does not make sense)
3.) If the score is smaller or equal to 70, or bigger or equal to 79, then grade = C (which does not make sense)
4.) If the score is smaller or equal to 60, or bigger or equal to 69, then grade = D (which does not make sense)
5.) If the score is smaller or equal to 0, or bigger or equal to 59, then grade = F (which does not make sense)
If you enter this algorithm into a programming language and provide it with sample scores, only scores from 90 to 100 returns a grade.

It just a bunch of if statements.

Your code should look like this. Run it with different values and then you will understand.

#include <iostream>
using namespace std;

int main ()
{
  char grade;
  int score;

  cout << "Please enter score: ";

  cin >> score;

  if (score >= 90 && score <= 100) grade = 'A';
  if (score >= 80 && score <= 89) grade = 'B';
  if (score >= 70 && score <= 79) grade = 'C';
  if (score >= 60 && score <= 69) grade = 'D';
  if (score >= 0 && score <= 59) grade = 'F';

  cout << "Your grade is: " << grade << endl;
}

// eof

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Don't Assume Everything is a Nail Just Because You Have a Really Big Hammer

Hi
This was the code that I did to simulate the algorithm before I posted my initial message (I sommer did it in QBasic because the only other language on my pc is Delphi which I don’t like):

-------------------------------------
score% = put_your_number_here
IF 100 >= score% AND score% >= 90 THEN grade$ = "A"
IF 80 >= score% AND score% >= 89 THEN grade$ = "B"
IF 70 >= score% AND score% >= 79 THEN grade$ = "C"
IF 60 >= score% AND score% >= 69 THEN grade$ = "D"
IF 0 >= score% AND score% >= 59 THEN grade$ = "F"

PRINT grade$
--------------------------------------

Why did you change the algorithm’s operators? What you wrote there is not what the algorithm states.

Algorithm Example:
If (score <= 80 && score >= 89) grade = ‘B’ ;

Your version:
If(score >=80 && score <= 89) grade=’B’;


Your version will work because you have fixed the algorithm (as common sense dictates)
Since the errata do not indicate that there are any problems with this algorithm, I would like think there is something else I’m missing (or maybe not)

Hi. I see you are not interpreting the pseudocode incorrectly:

100 ≥ SCORE ≤ 90

translates to

( 100 ≥ SCORE ) ≤ 90 becomes 100 >= SCORE and swap it to SCORE <= 100 (you are just swapping)

100 ≥ ( SCORE ≤ 90 ) becomes SCORE <= 90


so we then have

IF SCORE <= 100 AND SCORE >= 90

This is the correct way to write an if statement. The way you have done it is prone to failure (experience has taught me). I've debugged hundreds of lines due to this mistake.


BEWARE OF PSEUDOCODE: 100 ⪰ SCORE ⪯ 90 is very common and has more a mathematical background than development. Pseudocode has no standards or even guidelines and is merely a neutral way of writing a code concept.



PS: I have to edit this damn post cause the OSPREY upgrade is screwed with character underlines.

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Don't Assume Everything is a Nail Just Because You Have a Really Big Hammer

PS THIS IS WRONG:

IF 100 >= score% AND score% >= 90 THEN grade$ = "A" ... correct

IF 80 >= score% AND score% >= 89 THEN grade$ = "B" ... wrong
IF 70 >= score% AND score% >= 79 THEN grade$ = "C" ... wrong
IF 60 >= score% AND score% >= 69 THEN grade$ = "D" ... wrong
IF 0 >= score% AND score% >= 59 THEN grade$ = "F" ... wrong

THIS IS WHAT YOU SHOULD HAVE DONE:

IF 89 >= score% AND score% >= 80 THEN grade$ = "B"
IF 79 >= score% AND score% >= 70 THEN grade$ = "C"
IF 69 >= score% AND score% >= 60 THEN grade$ = "D"
IF 59 >= score% AND score% >= 0 THEN grade$ = "F"

You swapped the values around. Again do not put values before variables, experience has taught me and corrected you

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Don't Assume Everything is a Nail Just Because You Have a Really Big Hammer

The only part of the algorithm that is done correctly in the book is the Grade A test (which I so indicated) and now you use this as your example for the whole algorithm while ignoring the rest.
Let’s go through this again…
The book states:
If(100 >= score >= 90) grade = A *This is correct*
Then the book states:
If(80 >= score >=89) grade = B
But hang on… this is not right… should it not read:
If(89 >= score >=80) grade = B
And then the book states:
If(70 >= score >= 79) grade = C
But hang on…this is not right…should it not read:
If(79 >= score >= 70) grade = C
Need I go on?
The code that I wrote is obviously wrong and that is the whole point – it’s based on what the book says.

@hexium The code that I wrote is obviously wrong and that is the whole point – it’s based on what the book says.

OK, I see the problem. The pseudocode in the book can easily be misinterpreted.

You are correct in literally translating the pseudocode but there is no correction to this in their errata.

This algorithm is a classic example of the danger of pseudocode. Not everybody will interpret it the way you wrote it, or in this example, the way it was meant to be written, or is this intended?


I'm not knocking the principal, even I use it to document algorithms, but using LaTeX symbols can cause problems. I would rather have written:

if SCORE between (100 AND 90)

...because even if you swop it, if SCORE between (90 AND 100), you will still end up with the same code.

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Don't Assume Everything is a Nail Just Because You Have a Really Big Hammer

We are not discussing ancient ruins or musing over the meaning behind some 16th century play. Pseudo code is not supposed to be ambiguous. Are you sure that you had a good look at the algorithm before you replied the first time?

1) Agree that Pseudocode should never be ambiguous.

2) To be honest was not really paying much attention to the detail first time. I tend to filter out errors in pseudocode automatically as I'm use to working on daily bases with other peoples code.

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Don't Assume Everything is a Nail Just Because You Have a Really Big Hammer

Face the fact! We've all paid hundreds of rands for textbooks that are full of errors...

The options for answers to the questions is giving it away... Error in the textbook. Don't worry about it. You spot the mistake now feel good about yourselft.

Pick the answer you know the lectures want to see and get your one point

Had done that already before initiating this discussion
I would rather say that this is an indication of how necessary a subject like CSS101 is to BSc students.

Yes you are correct, this is a mistake in the textbook regarding Algorithm 8.3. The question will not be marked but you will get full credit for it.

In the previous edition the algorithm was phrased slightly differently but correct and we did not spot the change in this edition, sorry about this.

What am I missing? My textbook's version of Algorithm 8.3 in Chapter 8 of F & M (on page 148) is as follows:

1. if (the number is between 90 and 100, inclusive)
   then
     1.1 Set the grade to "A"
   End if
2. if (the number is between 80 and 89, inclusive)
   then
     2.1 Set the grade to "B"
   End if
...

Do I have a "wrong" version of the textbook? I feel cheated. I also want an incorrect textbook! Anyone want to swop?

The book is screwed .... it was mention somewhere in one of the posts. Marks for the question will be given for attempting the pseudo code and not for accuracy...

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Don't Assume Everything is a Nail Just Because You Have a Really Big Hammer

authors who sound like members of the taliban should be avoided

Its Bin Ladens way of bringing the American infadils down. Teach them such crapy CS that all their mainframes r belong to us.

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Don't Assume Everything is a Nail Just Because You Have a Really Big Hammer

rofl

"All your database are belong to us?"

cbrunsdonza Wrote:
-------------------------------------------------------
> The book is screwed .... it was mention somewhere
> in one of the posts. Marks for the question will
> be given for attempting the pseudo code and not
> for accuracy...

That is not what the lecturer said in this thread...

Look the problem is the text book has a serious error in its pseudo code. Most people will read it and then interpet it the way the author intended to write it.

You have 2 choices: Code 100% to the pseudo code and have a broken function; Or fix the pseudo code and have a function that works.

rdebruyn made the point that we should all work on: Pick the answer you know the lectures want to see and get your one point

Contact your lectures if you want to know what they want to see.

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Don't Assume Everything is a Nail Just Because You Have a Really Big Hammer

becked Wrote:
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> Yes you are correct, this is a mistake in the
> textbook regarding Algorithm 8.3. The question
> will not be marked but you will get full credit
> for it.
>
> In the previous edition the algorithm was phrased
> slightly differently but correct and we did not
> spot the change in this edition, sorry about this.