Cita:

D.W. van Meeuwen wrote:

Dear Emre,

You cannot change the counting variable using an assignment within a DO-loop. What you are trying to do in my opinion is leaving the DO-loop by setting the counter to the max. The correct way to exit a DO loop is the EXIT statement.
If this is not what you want, you might have a look at DO WHILE

Dirk

Thanks for a quick answer Dirk, the interesting thing is when I wrote exactly the same code in C++, I did not encounter any problem. I will try EXIT statement ( is it solely EXIT, or do I need any information (such as "go to" statement)), I think that do-while is more reliable solution. Thanks again for these ideas Dirk.

That is the solution:

integer function cornerio
real    :: term1, term2, term3, term4
i=1
do while (i==nelem)
!......
if(abs(term1)<=1e-20) then

term1=0.

end if

if(abs(term2)<=1e-20) then

term2=0.

end if

if(abs(term3)<=1e-20) then

term3=0.

end if

if(abs(term4)<=1e-20) then

term4=0.

end if
if( term1==0 .and. term2==0 .and. term3==0 .and. term4==0 ) then

cornerio=-1

i=nelem

else

if(term1/=0) then

if((term1*term2)>=0 .and. (term1*term3)>=0 .and. (term1*term4)>=0) then

cornerio=-1

i=nelem

end if
else if(term2/=0) then

if((term2*term1)>=0 .and. (term2*term3)>=0 .and. (term2*term4)>=0) then

cornerio=-1

i=nelem

end if
else if(term3/=0) then

if((term3*term1)>=0 .and. (term3*term2)>=0 .and. (term3*term4)>=0) then

cornerio=-1

i=nelem

end if
else if(term4/=0) then

if((term4*term1)>=0 .and. (term4*term2)>=0 .and. (term4*term3)>=0) then

cornerio=-1

i=nelem

end if
else

print*, "ERROR"

end if
end if 
i=i+1

end do
return
end function cornerio

Cita:

Les Neilson wrote:

Emre
In the code you supplied you replace the i=nelem statement with either
return
or
exit

RETURN will return from the function
but if you have any code you want executed after the end of the do-loop then
EXIT will end the do-loop

If you have nested do-loops then you can name each loop and exit "loop-name" will end that particular loop.
See the help for EXIT Statement.

Les

Also, thank you Les. There are a few solutions, I choose do-while as you can see above, it is correct right ?

I read all the comments, yeah do-while does not provide the same outputs, exit can be more reliable option.

Cita:

Steve Lionel (Intel) wrote:

Quote:

emreka82 wrote:

the interesting thing is when I wrote exactly the same code in C++, I did not encounter any problem.

That's because C++ is not Fortran. While a C++ "for" loop might look similar to a Fortran DO loop, and in many cases they are interchangeable, the semantics are really quite different.

A C/C++ for loop is much more like the Fortran DO WHILE - you specify start and end conditions and an expression that changes the loop variable each iteration. The end condition is an expression that is evaluated each time through the loop, and the increment variable is just that, a variable.

In a regular Fortran DO loop, it is in effect a counted loop where the count is determined before the loop ever starts execution, according to a formula specified in the standard. Once the loop begins execution, the count cannot be changed (at least not if you're following the standard.) In older compilers, you could sometimes change the loop control variable and have the effect you wanted, but most modern optimizing compilers don't let you do this.

The suggestions to use EXIT (also look up CYCLE) are the right way to go if you want to prematurely exit a loop (or skip iterations.)

Steve,
But a regular do while loop of C++ should have the same effect of do while-loop of fortran, right ? I mean both the figurative and the output of them. Such as;
C++:

int i=0;

do

{

	i++;

	cout<<"i:"<
	cout<
	cout<
} while((max*bodydiv)<=(domsize/pow(2.,unidiv+i)));

Fortran:

i=1
do  while((max*bodydiv)<=(domsize/(2.**(unidiv+i))))

	i=i+1

    print*, "i:", i

    print*, max*bodydiv

    print*, domsize/(2**(unidiv+i))

end do

Sorry for the c++ code above, I cannot write it inside the cpp code brackets.

Another thing came to my mind: Is there a difference between exit(EXIT_FAILURE); of C++ and exit of Fortran ? If so, then what should I use to have the same effect of exit(EXIT_FAILURE); in Fortran ?