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POFortran Pointer arithmetic
 

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    <p>That's my first question post ever ... don't be cruel, please.</p> <p>My problem is the following. I'd like to assign a fortran pointer as an expression. I think that's not possible by simple fortran techniques. But since new fortran versions seem to provide ways to handle things used in C and C++ (like c_ptr and c_f_pointer ... ), maybe someone knows a way to solve my problem. (I have not really in idea about C, but I read that pointer arithmetic is possible in C) To make things more clear, here is the code which came to my mind immediately but isn't working:</p> <pre><code>program pointer real(8),target :: a real(8),pointer :: b b=&gt;a*2.0d0 ! b=&gt;a is of course working do i=1,10 a=dble(i)*2.0d0 write(*,*)b end do end program </code></pre> <p>I know that there are ways around this issue, but in the actual program, all of which came to my mind, would lead to much longer computation time and/or quite wiered code.</p> <p>Thanks, a lot, in advance!</p> <p>Best, Peter</p>
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    1. CONot sure what you are trying to do, but in languages like c that allow pointer arithmetic the arithmetic is only addition/subraction. The "arithmetic" operates on memory address, so that `pointertoa + 1` yields a pointer to whatever is in the next memory loc after a. I dont think this is possilbe in fortran, but in any case your multiplication makes no sense.
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    2. COThanks for making the arithemtic clear. What I try to do is the following. I have a program depending on many input variables, and on of them is going o be changed inside of a do loop. But it depends on the input, which one is changed. However the loop construction is always the same and the parameters are stored in modules to be available in plenty of subroutines. Now I want to write some case construct after the parameter reading part to tell for the rest of the program which one is the parameter to be varied inside the loop, and in the loop I have a placeholder (here a).
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    3. COEverything would work perfectly, if the placeholder would follow the same expression for each parameter. Unfortunately it doesn't. Of course I can write an if clause to each point, where it is used, but a single decision point at the beginning of the program looks nicer, is more controlled (in the sence of errors done by myself or people who have to use the code in the future) and it's faster by means of calculation time. Sorry for the long answer, but you asked what I'm trying to do.
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