perl中的数学运算
2013-10-07 11:31:17 
阿炯
perl中以双精度(浮点数)保存和进行数值运算，就算写的是整数，在内部也会转换成等效的浮点数类型保存；但在perl内部，有些运算会将浮点数转换成整型进行，而且也有integer编译指令可以强制编译成整型。perl中整数有3种表示方式：
123
0123
61_123_234
这里使用下划线(_)代替逗号表示千分位，因为perl中逗号有特殊意义。
算术运算
+ - * / % **
**的优先级在这里最高。
取模时，先两个数取整，再取模。例如5.2%2.1等价于5%2。
多个取幂符号时，**的优先级是从右向左进行的。
3 ** 4 ** 2 # 3 ** (4 ** 2) = 3的16次方
需要对数字进行数学做的运算有：四舍五入、取整、取最小等。
Ceil
Cieling is basically outputing the next largest integer for an given real number.
返回比给出数字最近的且比它大整数。
ceiling(x) is the smallest integer not less than x. Ways to do it in Perl:
a)using our own logic
my $num=45.4;
my $ceil=int($num+0.99);
b)using POSIX
use POSIX qw/ceil/;
my $num=45.4;
my $ceil=ceil($num);
Floor
Flooring is outputing the next smallest integer for an given real number.
返回比给出数字最近的且比它小的整数。
floor(x) is the largest integer not greater than x.Ways to do it in Perl:
a)using our own logic
my $num=45.4;
my $floor=int($num);
b)using POSIX
use POSIX qw/floor/;
my $num=45.4;
my $floor=floor($num);
Round
Rounding is converting any floating-point number to the nearest integer.
它就是日常所说的四舍五入了。
Ways to do it in Perl:
a)using our own logic
my $num=45.4;
my $round=int($num + 0.5);
b)using Math::Round
use Math::Round qw/round/;
my $num=45.4;
my $round=round($num);
It'll be really nice if everyone crontributes to this thread with the equivalent functions in the language they are comfortable with.
123
0123
61_123_234
这里使用下划线(_)代替逗号表示千分位，因为perl中逗号有特殊意义。
算术运算
+ - * / % **
**的优先级在这里最高。
取模时，先两个数取整，再取模。例如5.2%2.1等价于5%2。
多个取幂符号时，**的优先级是从右向左进行的。
3 ** 4 ** 2 # 3 ** (4 ** 2) = 3的16次方
需要对数字进行数学做的运算有：四舍五入、取整、取最小等。
Ceil
Cieling is basically outputing the next largest integer for an given real number.
返回比给出数字最近的且比它大整数。
ceiling(x) is the smallest integer not less than x. Ways to do it in Perl:
a)using our own logic
my $num=45.4;
my $ceil=int($num+0.99);
b)using POSIX
use POSIX qw/ceil/;
my $num=45.4;
my $ceil=ceil($num);
Floor
Flooring is outputing the next smallest integer for an given real number.
返回比给出数字最近的且比它小的整数。
floor(x) is the largest integer not greater than x.Ways to do it in Perl:
a)using our own logic
my $num=45.4;
my $floor=int($num);
b)using POSIX
use POSIX qw/floor/;
my $num=45.4;
my $floor=floor($num);
Round
Rounding is converting any floating-point number to the nearest integer.
它就是日常所说的四舍五入了。
Ways to do it in Perl:
a)using our own logic
my $num=45.4;
my $round=int($num + 0.5);
b)using Math::Round
use Math::Round qw/round/;
my $num=45.4;
my $round=round($num);
It'll be really nice if everyone crontributes to this thread with the equivalent functions in the language they are comfortable with.