I'm struggling to convert a simple for loop from C to pascal. The code is shown below (as is a trace of the loop parameter values). I'm a bit puzzled how this should look elegantly in pascal. Anyone has an idea?

Regards, Darius

unsigned nc = 4;

for (unsigned i = 0, j = nc-1; i < nc; j=i++)
{

	cout << "i:" << i << endl;
	cout << "j:" << j << endl;

}

loop values are:
i:0
j:3
i:1
j:0
i:2
j:1
i:3
j:2

In our previous episode, Darius Blaszyk said:

Keep in mind that a C loop like

for (x;y;z)
{a}

is equal to Pascal's

x
while y do
  begin
    a
    z
  end;

there _is_ no general case with Pascal for.

so

i:=0;
j:=nc-1
while i<nc do
   begin
     writeln('i:',i);
     writeln('j:',j);
     j:=i;
     inc(i); // post increment, so j gets old version
   end;

I'm struggling to convert a simple for loop from C to pascal. The code is shown below (as is a trace of the loop parameter values). I'm a bit puzzled how this should look elegantly in pascal. Anyone has an idea?

IMHO the C code is short, but not elegant. It would be more elegant if the j=i is at the end.

Maybe:

var i,j: integer;
begin
  j:=nc-1;
  for i:=0 to nc-1 do begin
    writeln('i:',i);
    writeln('j:',j);
    j:=i;
  end;

Mattias

----- Oorspronkelijk e-mail -----

actualy, Marco's version is more correct. A C(++) for loop does it's evaluation on the fly, whereas in pascal (or some dialects), the for variable(s) are immutable or evaluated as early as possible. In this case it might work, but in general, a C++ for loop is better written as a pascal's "while ... do" of "repeat ... until" construct because of this.

consider a loop where you want to exit out of when a condition is met. In C(++) you can change the values of the for loop's variables on the fly et voila, on next iteration you return.

at least, that was what we were told in our CS courses, comparing C(++) vs Pascal/Modula/Oberon (almost 2 decades ago).

kind regards,
Dimitri Smits

Thanks to all. I got the code working now.

Regards, Darius