Cannot find a simple integral with Pascal

Question

I've written a programm to solve the integral X^2+2 by rectangles method

program fourrr;

var    a, b : real; { borders }
       h : real; { increment argument }
       s : real; { approximate value of the integral }
       n : integer; { number of intervals }
       x : real; { argument }
       y : real; { function value at the beginning of interval }
       i : integer;
begin

    write('lower border a: '); read(a);
    write('upper border b: '); read(b);
    write('increment argument h: '); read(h);

     n := (b - a) / (h + 1);
     x := a;
     s := 0;

    i := 1;
    while i <= n do
      begin
        y := x * x + 2;   // function value at the beginning of interval
        s := s + (y * h);
        x := x + h;
      end;

   writeln('Integral value: ', s); 
end.

but i cannot solve the problem with data types conversion when I run it.

So please help me it's very important. Thanks

For starters you might think about changing at least one of the elements in the loop termination condition within the loop. — 500 - Internal Server Error, Apr 10 '14 at 17:16
What exactly is the problem? What does "the problem with data types conversion" mean? In what way is the code not working for you? — Ken White, Apr 10 '14 at 22:19

score 0 · Answer 1 · answered Apr 10 '14 at 18:55

(Since the beginning, sorry for my bad english)

At the beginning, you need the input output: program fourrr(input,output);

I see that you done n := (b - a) / (h + 1); And that's not / , you should use " div " : n := (b - a) div (h + 1);

I don't know why did you use the loop ,and I tell you that I don't know how to solve that integral,but, if it's as you did, you don't need it. What you could change in the loop? Using the IF.

{ If i<=n THEN Begin y:=x * x + 2; // function value at the beginning of interval s := s + (y * h); x := x + h; end (*without the ; simbol*) Else writeln('ERROR'); (*The ELSE only read for him the writeln('error'), if you want to use more things , use the ELSE begin h:= ... ; alpha:=... If ...(<-for example) end;*)}

"At the beginning" is wrong; the program prompts the user for each input with `write`, and then reads the response from the console. You don't need any `program fourrr(input, output)`, because it's not getting the values as command line parameters. — Ken White, Apr 10 '14 at 22:18
Your advice: _And that's not / , you should use " div " : n := (b - a) div (h + 1);_ is wrong (even worse) and will produce another error because you **cannot** use `div` with floating point data types. Correct would be `n := round((b - a) / (h + 1));` — gammatester, Apr 11 '14 at 07:17

Cannot find a simple integral with Pascal

1 Answers1