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Many (I would venture to say, most) versions of FORTRAN do not support recursion. &nbsp;Recursion was first supported in FORTRAN 90, and in the real world not in all F90 implementations. &nbsp;First check the reference manual for the particular FORTRAN compiler to see if recursion is supported.<br />
<br />
If recursion is supported, then:<br />
<br />
sum(n) = n + sum(n-1)<br />
sum(0) = 0
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For the version that I am using, the recursion function seems to work. <br />
So when I try to write the recursive function, the Sum(n) is the function or is that the result?<br />
I know that the recursive function calls on itself, but is the Sum(n) the function?<br />
<br />
I was going to go about it this way:<br />
<br />
....<br />
recursive function Sumofnumbers(n) result(res)<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;implicit none <br />
<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;integer :: res, n, i<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (n .eq. 0) then<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;res = 0<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;else<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;do i = 1, n<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;res = Sumofnumbers(n) + n<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;end do<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;endif &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br />
end function Sumofnumbers<br />
....<br />
<br />
But I don't seem to get the right sum...
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Thank you Dr. Klahn! I am going to close this question, but I appreciate the help and I got my recursive code to finally work! Best, Cynthia.
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I am trying to write a recursive function in fortran that sums numberes 1 to n? I just need help with the function, I understand how to call from the main program...Thanks!
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I am trying to write a recursive function in fortran that sums numberes 1 to n? I just need help with the function, I understand how to call from the main program...Thanks!

Recursive function

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