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Logic problem

Posted on 2003-12-07
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Last Modified: 2012-05-04
      int k;
      int m;
      TRACE("%d ",!(iNewPlace>=(sLine.length()-1)));      //outputs 1

      TRACE("%d ",iNewPlace);      //outputs 0
      TRACE("%d ",sLine.length()-1);      //outputs -1

      TRACE("%d ",((iNewPlace>=(sLine.length()-1))));      //outputs 0

      TRACE("%d ",((m=iNewPlace)>=(k=(sLine.length()-1))));      //outputs 1

      TRACE("%d ",0>=-1);      //outputs 1

      k=iNewPlace;
      m=sLine.length()-1;
      TRACE("%d ",k>=m);      //outputs 1

Why is TRACE("%d ",((iNewPlace>=(sLine.length()-1))));      outputting false?
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Question by:Particleness
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bcladd earned 125 total points
ID: 9892317
iNewPlace and sLine.length() are unsigned. 0 - 1 is 0xffffffff which is -1 in two's compliment (signed int) but is a really big number as an unsigned int.

When the values are converted to integers (%d conversion or assignement to a signed int) you get signed comparison. Try comparing iNewPlace with m and I'll bet you get a signed/unsigned comparison warning from the compiler.

Hope this helps,
-bcl
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Author Comment

by:Particleness
ID: 9892338
sLine.lenth() was unsigned, but iNewPlace was signed. Nevertheless you  helped me out.
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