local variables

This is a discussion on local variables within the C++ Programming forums, part of the General Programming Boards category; if i declare a variable in a while statement, can that variable only be used by the whiel statement? i ...

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    local variables

    if i declare a variable in a while statement, can that variable only be used by the whiel statement? i tried doing that and then when i try to access the variable later in the program it says that it is not declared. is there any way to use a variable in a while statement and then still be able to access it outside of it?

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    declare the variable outside of the while.
    Code:
    int variable = 0;
    bool done = false;
    
    while(!done) {
      variable++;
      if(variable >5)
        done = true;
    }
    ?

  3. #3
    Open to suggestions Brighteyes's Avatar
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    if i declare a variable in a while statement, can that variable only be used by the whiel statement?
    Yep, the variables scope is restricted to the while loop and any nested blocks inside the loop.
    is there any way to use a variable in a while statement and then still be able to access it outside of it?
    If you need a variable outside of a loop, declare it outside of the loop.
    p.s. What the alphabet would look like without q and r.

  4. #4
    jasondoucette.com JasonD's Avatar
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    Re: local variables

    Originally posted by Gil22
    if i declare a variable in a while statement, can that variable only be used by the whiel statement?
    Yes, ANSI standard states that this is the case, and it logically makes sense. However, certain versions of MSVC++ allow the variable to be accessed after the loop - it is best to avoid this, since it is NOT part of the standard and your code may not compile on other compilers, or even on later versions of MSVC.

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    ok heres another question then.......i declared it outside of the variable but if i try to output it after the while statement then just junk comes out. its an array by the way, it outputs fine while i'm still inside of the loop but doesnt outside of it. any thoughts?

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    if it is an array, then you should output it through each individual element anyways. were you trying something like this?
    Code:
    int array[5];
    
    std::cout << array;

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    yea thats exactly what i was doing......cant you do that with an array and it will output what you put in it?

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    Originally posted by Gil22
    yea thats exactly what i was doing......cant you do that with an array and it will output what you put in it?
    i don't believe so.

    you'll need to loop through the array and output each individual element.

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    so you want the proggy to output every value in the array or what? for that i suggest doing
    Code:
      int array[5];
    for (int i=0;i<5;i++) 
      cout << w[i];
    hope i helped some
    the early bird gets the worm but the second mouse gets the cheese

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    it doesnt work for some reason.....here a small example of my code so you guys can see what i'm trying to do
    Code:
    while(top2 != NULL)
    	{
    		int i = 0;
    	    y[i] = top2->data;
    		cout << y[i];
    		listptr temp5;
    		temp5 = top2;
    		top2 = top2->link;
    		delete temp5;
    		i++;
    	}
    	char x[250];
    	cout << "enter a pattern";
    	cin >> x;
    	cout << y[1];

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    what part doesn't work? the while?

    how are you inputting x?

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    x works fine......its the cout << y[1] that screws up, it should output a simple character but it outputs a piece of junk instead. when i test the filling of the array inside the loop it works fine but when i try and do the same thing outside it doesnt work.

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    its in your while.

    try declaring int i = 0; outside of the while statement, as well as listptr temp5;

    then just increment i in your while, and assign temp5 like you are.

    the reason is that a new i gets declared with the value of 0 every time you start the while, and just overwrites y[0] everytime. and you are creating a new temp5 everytime you run through the while, whereforeas, you can save some memory and time through delcaring it outside as one temp5 is declared.

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    lol........i've been making some stupid mistakes lately. thats def it, thanks for helping me catch that.

  15. #15
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    Originally posted by Gil22
    lol........i've been making some stupid mistakes lately. thats def it, thanks for helping me catch that.
    no problem. i've done that too. kindof a hard catch at first, until ya start thinking about it.

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