15/100 is periodic number in binary (0.00 1001 1001 1001 ...) just like 1/3 is periodic in decimal (0.333...) . As such, it can't accurately be stored as a floating point number since that would take infinite storage. The number you think you have isn't quite what you think it is. 

$ perl -e'CORE::say sprintf("%.100f", 0.15) =~ s/0+\z//r'
0.1499999999999999944488848768742172978818416595458984375

$ perl -e'CORE::say sprintf("%.100f", (1.15*170)+0.50) =~ s/0+\z//r'
195.999999999999971578290569595992565155029296875

[download]
(Upd: syphilis points out %.100g naturally remove the trailing zeros.)

See What Every Programmer Should Know About Floating-Point Arithmetic. It covers how to handle this.

In reply to Re: int() function by ikegami
in thread int() function by geoperl

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