CODEWITHSUNDEEP
delphiconsolepascal
Chunky1318
Chunky1318

Reputation: 113

Pascal for loops within repeat loops

you've all been so helpful so far, so heres another annoying problem for you!

I've got a basic word guessing game, written in Pascal for a console in Delphi 7, where the guesses (right or wrong) are stored in a fixed array named "guesses" now what i need to do is test to see if they have guessed that letter already. I have the following code...

Write ('Guess a letter: ');
Readln (guess);
Guess := UpCase(Guess);
repeat
  for i := 1 to 20 do
  begin
    if guess = guesses[i] then
      begin
        guessed := true;
      end
    else begin
      guessed := false;
    end;
  end;
until (guessed = true) or (i = 20) ;

My problem is it follows the for loop 20 times, and should end as it is the first letter and is not in the "guesses" array, but keeps repeating. after its looped the for loop 20 times and found no entry of the guess letter, it should exit with the boolean "guessed" as false.

Thanks in advance for your help!

Upvotes: 5

Views: 2897

Answers (2)

Warren P
Warren P

Reputation: 68872

The code you have written makes no sense.

  1. To exit the for loop when you find your guess, add a break below the guessed := true.

  2. Why are you repeating the same logic infinitely using one condition that will always be true, and one condition that might easily be never true? I'm guessing you've shown part of your code inside that repeat loop, and not all of it. In that case, a good convention on stackoverflow for code samples is to put in something like: do_something_here(); in the place where you really have 100 more lines you didn't want to show here.

  3. It would be great if you showed the var declarations so we can see your types.

Your code would make sense again if:

  1. You break from the for loop.
  2. You only need to do the While loop if you do something variant in each case, such as ask the user to input some new input.

here's some code that does something at least useful:

(1) it will ask you to enter something, and repeat until you enter something that matches an element in the hard coded list.

(2) It will terminate, given certain inputs from you, unlike your code which may never terminate. It also doesn't waste time in the for loop on the other elements once it finds a match.

(3) It shows trivially that you should validate the inputs, or you will have exceptions. What if you entered nothing and just hit enter in your code? You would get an endless loop.

procedure Demo;
var
  guess:Char;
  guesses:Array of Char;
  i: Integer;
  guessed:Boolean;
begin
 repeat
  setup_guesses(guesses); // not shown
  Write ('Guess a letter: ');
  Readln (guess);
  Guess := UpCase(Guess);
  if (Ord(Guess)>='A') and (Ord(Guess)<='Z') then begin
   guessed := false;
   for i := Low(guesses) to High(Guesses) do // why hard code 1..20???
   begin
     if guess = guesses[i] then
       begin
         guessed := true;
         break;
       end;
   end;
  end;
 until (guessed = true);
 if guessed then
   WriteLn('An element in guesses matched your input')
 else
   WriteLn('No element in guesses array matches your input')
end;

Upvotes: 9

jordani
jordani

Reputation: 436

My problem is it follows the for loop 20 times, and should end as it is the first letter and is not in the "guesses" array, but keeps repeating. after its looped the for loop 20 times and found no entry of the guess letter, it should exit with the boolean "guessed" as false.

You can not use loop variable I outside for loop:

Pascal For Loop

Design Choices: Loop var must be an ordinal type of usual scope

After normal termination, loop var is undefined

The loop var cannot be changed in the loop

The loop parameters can be changed, but they are evaluated just once, so it does not affect loop control

http://courses.cs.vt.edu/~cs3304/Spring00/notes/Chapter-7/tsld026.htm

Upvotes: 7

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