Arrarys

I am reading in two text files, and placing the contents into an array element. In my code I am prompting the user for the number of students and questions. I am then to randomly select a student and question and output to the screen. Continue this until a 0 or -1 is entered.

I have written code but I am not sure if it is correct. Can someone please take a look and tell me how far off I am and what corrections need to be made. Thanks.

inFile=fopen('student.txt','r');

inFile2=fopen('testQuestion.txt','r');

flag=-1;

index=0;

student=[];

testQuestion=[];

while~feof(inFile)

      index=index+1;

      line=fgetl(inFile);

end

while~feof(inFile2)

      index=index+1;

      line=fgetl(inFile2);

end

while student~=-1

      student=rand(1,5);

end

while testQuestion~=-1

      testQuestion=rand(1,5);

end

fprintf('%s',student)

fprintf('%s',testQuestion)

Answer 1

[Walter Roberson]

while~feof(inFile)

should not be relied upon to be accepted in future versions. You should use a space between the while and the condition.

You are using feof() as if it predicts end-of-file, as if after after the last item in the file is read, the I/O routines would look ahead and see that nothing is left and would set the feof flag. Anything based upon the C or C++ I/O libraries or upon the OpenGroup Unix Standards or upon the POSIX standards (and MS Windows claims POSIX conformance in this regard) never does that kind of "look-ahead". Instead, feof is not set until an I/O operation attempts to read data and there is absolutely no data available. Therefore, each time you fgetl() you need to test whether that was the I/O that found end-of-file. And it turns out that the easiest way to do that does not need feof at all:

while true
  line = fgetl(inFile);
  if ~ischar(line)  %at EOF, non-char is returned
    break;
  end
  index = index + 1;
end

I admit to being puzzled as to why you are not storing the content of the lines you read...

You initialize

student=[];
testQuestion=[];

If you do some testing, you will find that

if [] == -1

and

if [] ~= -1

are both false. Perhaps you meant to set student and testQuestion to something along the way, but we cannot tell what.