See: What Every Computer Scientist Should Know About Floating-Point Arithmetic.

If I run 

printf("%.16f\n",100 * 5.1);

[download]
I get the output 
509.9999999999999400

[download]
The difference is that normal print does a formatted round (I think %.8g) that rounds up to 510, whereas %d casts it as a signed integer, a.k.a. performs a floor and rounds down to 509.

#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

In reply to Re: Different values while applying format specifiers by kennethk
in thread Different values while applying format specifiers by perlmonksuser

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