我正在寻找Perl内置函数），但挖掘进一步证明这是错误的：
> /usr/local/bin/perl5.10.1 -e'print（sprintf（％。2f，shift @ARGV）。\\\
）;'0.335
0.34
> /usr/local/bin/perl5.10.1 -e'print（sprintf（％。2f，shift @ARGV）。\\\
）;'1.335
1.33
$ div $解析方案 DB< 1> $ a = 0.335
DB< 5>打印sprintf（％。19f，$ a）
0.3350000000000000200
DB< 7> $ b = 1.335
DB< 8>打印sprintf（％。19f，$ b）
1.3349999999999999645
DB< 9>
$ b由于0.335在内部表示为略大于0.335，所以转换为0.34，而1.335略低于LESS超过1.335，所以涨到了1.33。
I was out looking for the rounding convention used by Perl's built-in function sprintf.
I was thinking that it does a normal rounding (e.g. ROUND_HALF_UP as in Java's rounding mode convention), but digging further proved this to be wrong:
> /usr/local/bin/perl5.10.1 -e 'print(sprintf("%.2f", shift @ARGV)."\n");' 0.335
0.34
> /usr/local/bin/perl5.10.1 -e 'print(sprintf("%.2f", shift @ARGV)."\n");' 1.335
1.33
解决方案 You have been bitten by the fact that floating point numbers are not exact representations of decimal fractions. Here's what I get:
DB<1> $a=0.335
DB<5> print sprintf("%.19f",$a)
0.3350000000000000200
DB<7> $b=1.335
DB<8> print sprintf("%.19f",$b)
1.3349999999999999645
DB<9>
Since 0.335 is represented internally as slightly larger than 0.335 it rounds to .34, while 1.335 is slightly LESS than 1.335, so it rounds to 1.33.
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