Thread: How do you write your own looping function?

  1. #1
    0x7f
    Guest

    Question How do you write your own looping function?

    Its that time again. time for another one of my weird questions. This one is a real gem. Im plotting to write my own foreach function (ya im a perl nut, tuff.) however writing a function that takes code i guess in {}'s isnt exactly standard material for C++ books to cover. Im not even sure what to call this type of function. the end result im aiming for is something like:

    foreach(T bob, vector<T>) { dothis(with bob); }

    my thoughts were templating as much as i can so it could take arrays or vectors or possibly other STL containers. am i completely nutty in wanting to write my own looping function? or is this even do-able? oh well, im dieing to hear what you guys have to say.

    me.

  2. #2
    Open to suggestions Brighteyes's Avatar
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    The STL already offers a for_each function
    Code:
    #include <iostream>
    #include <algorithm>
    
    using namespace std;
    
    void print(int);
    
    int main()
    {
        int array[9] = {1,2,3,4,5,6,7,8,9};
    
        for_each(array, array + 9, print);
    }
    
    void print(int num)
    {
        cout<< num <<' '<<flush;
    }

  3. #3
    0x7f
    Guest

    Angry =(

    aww your taking all the fun out of it, the entire point of writing it is to figure it out HOW to write it, not to auctually use it for anything. =P

  4. #4
    Hardware Engineer
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    For looping in general, take a look at the tutorials (lesson 3).

  5. #5
    0x7f
    Guest
    not USING loops, im talking about writing a function that IS a loop.

  6. #6
    Open to suggestions Brighteyes's Avatar
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    not USING loops, im talking about writing a function that IS a loop.
    But the function that IS a loop, uses a loop. The definition of for_each is this
    Code:
    template <typename In, typename Op>
    Op for_each(In first, In last, Op f)
    {
        while (first != last)
            f(*first++);
    
        return f;
    }
    The only way to create a loop without using while, for, or do/while is to fake it with goto or recursion. Even Perl's foreach is implemented with a loop, check the source code if you don't believe me.

  7. #7
    0x7f
    Guest
    im aware of that, and i never thought i would go without using a while loop in it, however my question centers on how do you pass what you want your function to do? I have no clue how to pass whats in the {}'s. The loop needs something to do, and thats what im really looking for.

  8. #8
    Open to suggestions Brighteyes's Avatar
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    I have no clue how to pass whats in the {}'s. The loop needs something to do, and thats what im really looking for.
    How about a place to start, a place to end, and the operation to perform on that sequence?

  9. #9
    The Pantless Man CheesyMoo's Avatar
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    Hahaha.
    If you ever need a hug, just ask.

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