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++ operator on arrays

This is a discussion on ++ operator on arrays within the C Programming forums, part of the General Programming Boards category; Hey Everyone, Just began programming C and am working through the 'white bible'. Have programmed in LISP and Java prior ...

  1. #1
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    ++ operator on arrays

    Hey Everyone,

    Just began programming C and am working through the 'white bible'. Have programmed in LISP and Java prior to this. I have a question regarding the incrementer operator and its usage with arrays. Ex:

    Code:
    value = ++myarray[maxvalue - 1];
    What exactly is being incremented here?

    I haven't seen an increment operator used in this way before!

    Cheers

    BIOS

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    You are incrementing the value at myarray[maxvalue -1] and then assigning it to the variable value.

    For example:
    Code:
    int myarray[4] = {1,2,3,4}
    
    x = ++myarray[2];
    myarray[2] is 3 (remember C arrays index from 0, not 1)
    3 + 1 equals 4 myarray[2] ends up being 4
    assigning to x makes it 4

    (I sometimes find it helpful to substitute real numbers for the variables as a way to understand things)
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    Hey thanks for the reply!

    That makes perfect sense. Thanks for the explanation. I think it was the fact that you can place the increment operator as a prefix in C that threw me. I.e. in Java you would write:

    Code:
    myarray[x]++;

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    Quote Originally Posted by BIOS View Post
    Hey thanks for the reply!

    That makes perfect sense. Thanks for the explanation. I think it was the fact that you can place the increment operator as a prefix in C that threw me. I.e. in Java you would write:

    Code:
    myarray[x]++;
    C has both prefix and postfix in this case... The difference being this...
    Code:
    int myarray[4] = {1,2,3,4}
    
    x = ++myarray[2];   // x = 4, myarray[2] = 4
    
    x = myarray[2]++;  //  x =3, myarray[2] = 4
    The difference is whether myarray[2] is incremented before the assignment or after...

    Also let me toss in just a small note of caution here... Beware of comparing languages! ... Java does a lot of babysitting that C does not, it also has features C does not. C gives you control over code that is hidden in Java, it can also do some stuff Java cannot... Whenever possible, you should treat your C learning experience as something entirely new and different...
    Last edited by CommonTater; 09-04-2011 at 10:11 AM.
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    Quote Originally Posted by CommonTater View Post
    C has both prefix and postfix in this case... The difference being this...
    Code:
    int myarray[4] = {1,2,3,4}
    
    x = ++myarray[2];   // x = 4, myarray[2] = 4
    
    x = myarray[2]++;  //  x =3, myarray[2] = 4
    The difference is whether myarray[2] is incremented before the assignment or after...
    Interesting! I had been wondering why C allowed this.

    Quote Originally Posted by CommonTater View Post
    Also let me toss in just a small note of caution here... Beware of comparing languages! ... Java does a lot of babysitting that C does not, it also has features C does not. C gives you control over code that is hidden in Java, it can also do some stuff Java cannot... Whenever possible, you should treat your C learning experience as something entirely new and different...
    This is great advice. Actually the reason I'm learning C is for this extra control and the greater awareness it brings with regard to managing memory etc. I must remember not to fall into that 'comparison' trap! Thanks alot.

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    Quote Originally Posted by BIOS View Post
    This is great advice. Actually the reason I'm learning C is for this extra control and the greater awareness it brings with regard to managing memory etc. I must remember not to fall into that 'comparison' trap! Thanks alot.
    One thing I can promise you... C will make you a very careful programmer. Almost everything is on you to get it right.

    (But I wouldn't have it any other way )
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    Quote Originally Posted by CommonTater View Post
    One thing I can promise you... C will make you a very careful programmer. Almost everything is on you to get it right.

    (But I wouldn't have it any other way )
    Considering my troubles understand C/C++ pointer concepts (one could say I am just stupid ) I have come to the conclusion that those languages were made by masochists for masochists :P
    You ended that sentence with a preposition...Bastard!

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    Quote Originally Posted by Eman View Post
    Considering my troubles understand C/C++ pointer concepts (one could say I am just stupid ) I have come to the conclusion that those languages were made by masochists for masochists :P
    Ok... start a thread for pointers, show us some code... we'll see what we can do.

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    Quote Originally Posted by CommonTater View Post
    Ok... start a thread for pointers, show us some code... we'll see what we can do.
    I assume you don't visit the C++ forum much, I have posted several pointer questions but most related to polymorphism...getting clearer though.
    Btw, how goes your learning C++?
    You ended that sentence with a preposition...Bastard!

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    Quote Originally Posted by Eman View Post
    I assume you don't visit the C++ forum much, I have posted several pointer questions but most related to polymorphism...getting clearer though.
    Btw, how goes your learning C++?
    I read the C++ section but rarely post there. Since I gave up on C++ entirely --it just doesn't make any sense to me-- it doesn't seem right that I should post there... well, except maybe to ask questions.
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    Quote Originally Posted by CommonTater View Post
    I read the C++ section but rarely post there. Since I gave up on C++ entirely --it just doesn't make any sense to me-- it doesn't seem right that I should post there... well, except maybe to ask questions.
    And here I thought I was the only one. The only reason I am learning it is for the sake of learning it..some say it will make sense when I start working. I hope they're bloody right. Java is even worse.
    Hopefully, you will go back to it one day man
    You ended that sentence with a preposition...Bastard!

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    AFAIK Java also have both post and pre increment operators, which also change the operator precedence related to the assignment operator.

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    Yes, it does..But I was talking about the OOP style in java..Everything is OOP and it takes a while to find what I need. I hate it..
    If you have a string you can't modify a character in the string for example. I have to look for some other class. I hate that language..
    You ended that sentence with a preposition...Bastard!

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    Quote Originally Posted by Eman View Post
    Yes, it does..But I was talking about the OOP style in java..
    I was referring to post #3, I should have made a quote to that post, sorry for the confusion.

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