Re: Simple Program, Lots of Issues (F90)

ALevenson wrote:
>>> prime specific hint.
>>>          write (*,*) 2
>>>         do i = 3 , x, 2
>>> If you do that, you won't have to worry about the evenness
>>> stuff, just test the odd numbers starting at 3.
> 
> Normally I do that, but I wanted to do some tests and see just how
> fast Fortran can be compared to say, Perl.
> 
>>>          j = i / 2
>>>          t = i / 2
>>>          if ( j == t ) then
>> Why would you ever expect j and t to be different?  Division
>> is usually repeatable on most machines ;) .>
> 
> I'm probably wrong, but if i is 3, wouldn't j = 1, while t = 1.5?

Where i = 3, 3 / 2 (integer division) = 1.  Assigning to t then gives 
you j = 1, t = 1.0.

As I noted previously, if you do 3 / 2.0 instead, then you get the 
desired 1.5.

> It
> was my way of testing to see if it was an even divisor, because I
> wasn't sure if Fortran had an Int() function.
> 
> Also, I getting the errors:
> 
>   primes.f90:38.33:
> 
>            if ( notprime == .FALSE. && even == .FALSE. ) then
>                                 1
>   Error: Syntax error in IF-expression at (1)

It's probably upset about the "&&".  If you fix that, I think it will 
then be upset about using == on a LOGICAL.

>   primes.f90:40.12:
> 
>            end if
>              1
>   Error: Expecting END DO statement at (1)
>   primes.f90:26.21:
> 
> And I am not really sure what to make of either. For the second one,
> did I nest too deeply? I am pretty sure that should be an end if, not
> an end do.

The second is a byproduct of the first; because the IF did not process 
cleanly, the compiler has ignored it, and consequently is not expecting 
the END IF.