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Fortran 77 help making an empty array (or blank list if they exist in fortran)

  1. Aug 9, 2011 #1
    I need to create an empty array but the length of the array is determined by the start and end numbers entered by the user

    for example if the range of numbers the user was interested in was 4-10 inclusive then i want the array to be of length 7

    How to I go about doing this?

    Other languages (Python for example) have the option to create an empty list and then values can be added to the list as many times as is required. Is there any similar function in fortran 77?

    Thanks in advance for any help!!
  2. jcsd
  3. Aug 9, 2011 #2


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    Staff: Mentor

    Fortran 77 doesn't have dynamically-allocated arrays. You have to anticipate the maximum bounds of the array, and declare it accordingly. You can declare

    REAL MYARRAY(4:10)

    which allocates memory for seven REALs, MYARRAY(4) through MYARRAY(10), but this allocation is fixed.
    Last edited: Aug 9, 2011
  4. Aug 9, 2011 #3


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    Science Advisor

    Remember that an interpreted language like python has somewhat of an advantage over a compiled language like fortran in this regard, since you don't have quite the same distinction between compile time and run time with an interpreter. In fortran array lengths have to be defined at compile time.
  5. Aug 9, 2011 #4


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    Homework Helper

    Many implementations of Fortran 77 have extensions to handle dynamic memory allocation, using a POINTER statement to declare the variables and a function (probably called MALLOC} to allocate space. This isn't "ANSI standard Fortran 77", but enough compilers support for it to be a de facto portable standard. Of course if you only plan to run your code on your own computer system, you might not care if it is portable, so long as it works for you!
  6. Aug 14, 2011 #5
    You should try that in Fortran 90 or later compiler,
    which have allocatable arrays. Even later versions (after Fortran 95)
    have allocate on assignment, arrays can grow.

    There are several free Fortran 95 compilers.
  7. Mar 15, 2012 #6
    If you're going to use it to store numbers, then maybe you could make it an array of 0's. You could probably define an array of some large dimension, and then when you get the limits (4-10, in your example) from the user, you could calculate the difference between them and make a zeros array of that size. If your user inputs 4&10, say, then you could calculate the difference of the two (you might want to add 1 to it to make it inclusive). If d is the difference between the two, then maybe you could generate an array(d) with all zeros using a do-loop.

    Hope this was useful.
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