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POIf-else block and unexpected results with float datatype. [Edited with one more question]
 

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  1. POIf-else block and unexpected results with float datatype. [Edited with one more question]
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    <p>I compiled the following program with gcc 4.4.1 and I get unexpected output (Well, unexpected for me)</p> <pre><code>#include&lt;stdio.h&gt; int main() { float x=0.3, y=0.7; if(x==0.3) { if(y==0.7) printf("Y\n\n"); else printf("X\n\n"); } else printf("NONE\n\n"); } Output: NONE </code></pre> <hr> <pre><code>#include&lt;stdio.h&gt; int main() { float x=0.3, y=0.7; if(x&lt;0.3) { if(y==0.7) printf("Y\n\n"); else printf("X\n\n"); } else printf("NONE\n\n"); } Output: NONE </code></pre> <hr> <pre><code>#include&lt;stdio.h&gt; int main() { float x=0.3, y=0.7; if(x&gt;0.3) { if(y&gt;0.7) printf("Y\n\n"); else printf("X\n\n"); } else printf("NONE\n\n"); } Output:X </code></pre> <p>So, it's clearly visible that the stored value in "x" is greater than 0.3 and the stored value in "y" is less than 0.7</p> <p>Why is this happening? Is this a property of float datatype or the if-else statements interpret float in a different way?</p> <p>Thanks.</p> <hr> <p>Edit: Alright, I pondered it over and I'm getting a little confused now. Kindly tell if my understanding of this problem is correct or not.</p> <pre><code>float x=0.3; </code></pre> <p>This stores <code>x=0.30000001192092895508</code> in the memory. Clearly, this is greater than <code>0.3</code> (Is this correct?) </p> <p>Now, <code>double x=0.3</code> results in <code>x=0.29999999999999998890</code> and this is smaller than 0.3 (Is this correct too?)</p> <p>Main question: So if I use store <code>0.3</code> in <code>float x</code>, then the following statement <code>if(x&gt;0.3)</code> results in <code>x=0.30000001192092895508</code> being implicitly casted as a double and 0.3 is also a double instead of a float. Hence <code>0.3=0.29999999999999998890</code> and the internal operation is <code>if((double) 0.30000001192092895508 &gt; (double) 0.29999999999999998890)</code>. Is this correct?</p>
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    1. USNaruto Uzumaki
    1. USNaruto Uzumaki
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    1. COPlease append "f" to the float values and post the results. If known it from Java, that the floating numbers not explicitly defined with "f" as an float will get an double. Probably some strange things happen when casting between float and double. It could be that 0.3 becomes to 0.30000000000000001 due to some rounding error.
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      1. POIf-else block and unexpected results with float datatype. [Edited with one more question]
      1. USMarc-Christian Schulze
    2. COBetter yet, change all your variables to `double`. All the math functions in C return `double`, so you might as well be consistent. `float` is only useful for saving memory when you have an array of millions of them.
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      1. POIf-else block and unexpected results with float datatype. [Edited with one more question]
      1. USdan04
 

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