Syntax error when using “X != 0” in Fortran

Question

I have a problem with my Fortran program that does nothing more than calculating a prime factorization (or should do). That\'s the error:

C:\\MinGW\\Fortran>         


        

Answer 1

The token for "not equals" in fortran is /= . ! starts a comment, hence the compiler reading line 15 as

        if (prim(i) 

and so is confused because there is no bracket to close the logical expression in the if statement. So simply replace != with /= and it should get rid of this problem.

Answer 2

You're using the wrong notation for 'not equal to'. Fortran syntax is /= or .NE..

So you should be using:

if (prim(i) /= 0 .and. modulo(n, prim(i)) == 0) then

and

if (prim(i) /= 0) then

Furthermore, your syntax of integer(sqrt(real(m))) is incorrect, perhaps you mean NINT(sqrt(real(m)))?

Answer 3

Well, this is Fortran and ! denotes a comment. So the compiler actually sees

if (prim(i) 

which is no valid statement. The error message you see reflects that.

"Not equal" in Fortran is /= or .ne.:

 if (prim(i) /= 0 .and. modulo(n, prim(i)) == 0) then

and, later on:

if (prim(i) /= 0) then