Isn't this puzzling?

This is a discussion on Isn't this puzzling? within the C++ Programming forums, part of the General Programming Boards category; I intend to read several numbers into the array of X and then several others into the array of Z; ...

  1. #1
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    Isn't this puzzling?

    I intend to read several numbers into the array of X and then several others into the array of Z; however, it happens that the following codes can correctly read X but not Z. Only after I change the 'i' in the second loop to 'j' will both read correctly. This is the only 'for' loops in my function.


    Code:
         for (int i=0; i<dimofX_model; ++i) 
    	 	{
            	readfile>>temp.X[i];
             }
         //read in the X variables;
         
    	 for (int i=0; i<dimofZ_model; ++i)		
         	{
    			readfile>>temp.Z[i];
    		}
         //read in the Z variables

  2. #2
    Devil's Advocate SlyMaelstrom's Avatar
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    Hmm... I guess your compiler doesn't conform to the scoping rules of for statement initializations. Unless, I'm missing something.
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  3. #3
    The superhaterodyne twomers's Avatar
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    What compiler are you using? It's odd alright.

  4. #4
    carry on JaWiB's Avatar
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    Using VC6? It's probably what Sly says. Does this work as expected?
    Code:
    {
    for (int i=0; i<dimofX_model; ++i)
    {
      readfile>>temp.X[i];
    }
    }
    //read in the X variables;
    {   
    for (int i=0; i<dimofZ_model; ++i)		
    {
      readfile>>temp.Z[i];
    }
    }
    //read in the Z variables
    "Think not but that I know these things; or think
    I know them not: not therefore am I short
    Of knowing what I ought."
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  5. #5
    The superhaterodyne twomers's Avatar
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    Try this -

    Code:
    int i=0;
    
    for (i=0; i<dimofX_model; ++i) 
    {
        readfile>>temp.X[i];
    }
    
    for (i=0; i<dimofZ_model; ++i)		
    {
        readfile>>temp.Z[i];
    }
    and tell us if that works.

  6. #6
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    yeah, the last suggestion works. I'm using DevC++. Isn't that disturbing?

  7. #7
    carry on JaWiB's Avatar
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    That's very odd. What version of Dev-C++ do you have? I wasn't aware of any for loop issues like VC6 has.

    In any case, you might want to consider an IDE switch; perhaps to Code::Blocks or Visual C++ Express 2005. I believe there is no longer any active development in Dev-C++
    "Think not but that I know these things; or think
    I know them not: not therefore am I short
    Of knowing what I ought."
    -John Milton, Paradise Regained (1671)

    "Work hard and it might happen."
    -XSquared

  8. #8
    The superhaterodyne twomers's Avatar
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    Aye, 'tis very odd ... :/ Did you try it with a while() loop?

  9. #9
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    By the way, I forgot to say: after I changed it to 'j', compile it and it works; after that I changed it back to 'i', compile it and it works too. Is this helpful for tacking the issue?

  10. #10
    carry on JaWiB's Avatar
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    > By the way, I forgot to say: after I changed it to 'j', compile it and it works

    Perhaps you made other changes before this, and for some reason the project wasn't recompiled to reflect those changes. If I recall correctly, I used to have issues with Dev in this respect (making changes, hitting "Compile and Run," but not actually having the files compiled/linked)
    "Think not but that I know these things; or think
    I know them not: not therefore am I short
    Of knowing what I ought."
    -John Milton, Paradise Regained (1671)

    "Work hard and it might happen."
    -XSquared

  11. #11
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    You don't mean to say g++ contains bugs like these... JaWiB, the IDE has nothing at all to do with this issue.
    Code:
    #include <stdio.h>
    
    void J(char*a){int f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){
    puts(a);return;}for(;c<='9';++c){for(f=0;f<9;++f)if(a[i-i%27+i%9
    /3*3+f/3*9+f%3]==c||a[i%9+f*9]==c||a[i-i%9+f]==c)goto e;a[i]=c;J(a);a[i]
    ='0';e:;}}int main(int c,char**v){int t=0;if(c>1){for(;v[1][
    t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return 1;}

  12. #12
    Registered User MacNilly's Avatar
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    Quote Originally Posted by JaWiB
    > By the way, I forgot to say: after I changed it to 'j', compile it and it works

    Perhaps you made other changes before this, and for some reason the project wasn't recompiled to reflect those changes. If I recall correctly, I used to have issues with Dev in this respect (making changes, hitting "Compile and Run," but not actually having the files compiled/linked)
    This is obviously the case. If you don't use rebuild all sometimes the compiler will not reflect ALL the changes you made and saved earlier.

  13. #13
    and the hat of int overfl Salem's Avatar
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    Yeah, sometimes a rebuild all is a good idea just to make sure everything is up to date.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  14. #14
    The superhaterodyne twomers's Avatar
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    Also, you could save the hassle of needing two for loops if you did something like this:

    Code:
    int i=0; // Could prob get rid of this and put it inthe for loop
    
    for (i=0; i<dimofX_model; ++i) 
    {
        readfile>>temp.X[i];
        readfile>>temp.Z[i];
    }
    if you saved the file from which you're reading as follows -

    Code:
    XVar1 ZVar1
    XVar2 ZVar2
    XVar3 ZVar3
    XVar4 ZVar4
    XVar5 ZVar5
    ...
    XVarN ZVarN
    Obviously all the X and Y vars are numbers (I'm assuming). You don't even need them on new lines if you don't want to. I just thought I'd throw that out there.

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