for loops - newbie q's

This is a discussion on for loops - newbie q's within the C Programming forums, part of the General Programming Boards category; I understand that for loops are used as for(variable = value)(relational expression)(inc dec value) {loop} my question is, do you ...

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    for loops - newbie q's

    I understand that for loops are used as
    for(variable = value)(relational expression)(inc dec value) {loop}

    my question is, do you have to increment or decrement the variable set at the first of the function? and do you even have to set a variable at all? Like could you just say..
    for (i != 0) {loop that modifies i} ..or would that just be a for loop acting as a while loop.

    I cant see a whole lot of uses for the for loop.. from what I see it's just a while loop with a preset number of loops.

    could anyone give me a simple example of other uses for the for loop besides the plain for(i = 1)(i <=20) (i++)

  2. #2
    & the hat of GPL slaying Thantos's Avatar
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    The good thing about for loops is that they do three functions in one. They set the starting value, evaulate the expression, and make the incremental change.
    With a while loop you have to set the value before the while loop and make sure you put in the incremental change in the loop. I can't count the number of times I've forgotten to put the incremental change in a while loop.
    Every different typle of loop has its strong points and weak points. Just need to identify them and use the best loop for the job.

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    so the only valid expression on the third part of the function is (var)++ or (var)--?

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    & the hat of GPL slaying Thantos's Avatar
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    Nope, you can do other ones.
    ie

    for(i=0;i<x;i+=15)

    It seems like you can do any math function. I don't know all the limits but i++ or i-- are not the only ones that can be done.

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    >I cant see a whole lot of uses for the for loop.. from what I see it's just a while loop with a preset number of loops.

    A for loop is a subset of the while loop - a for loop is only used for counter-controlled repetition, and has very little other use. A while loop can be used for counter controlled repetition, but not very often. Normally a while loop is used to evaluate a condition, like an if/else statement.

    Code:
    while (condition1 == true){
      do(someaction)
    }
    while (condition 1 !=  true){
      do(someotheraction)
    }
    Try here for some examples of the for loop (go onto the other sections as well).

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    With for loops, you can have a loop without the increment value, without the condition, without the intialization, or any combination of two, or none of the above.

    Code:
    for(  ;  ;  )   /*empty*/
    {
       if(condition) break;
    }
    
    i = 0
    for(; i < 5; ) /*conditional only*/
    {
        printf("%d", i++);
     }
    Just two of the permitations of the for loop.

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    Thats pretty cool bigtamscot, never knew that. Of course in both cases I would have used a while loop.

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    aurė entuluva! mithrandir's Avatar
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    >Of course in both cases I would have used a while loop

    Well a while loop generally saves you time, but bigtamscot is right in what he's saying.

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    Ofcourse we would use a while loop first of all, just demonstrating flexability of for loop.
    Last edited by bigtamscot; 09-26-2001 at 06:36 AM.
    hoping to be certified (programming in c)
    here's the news - I'm officially certified.

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