极客教程Perl log() 函数
Perl中的log()函数返回传递给它的数值的自然对数。如果调用时没有传递数值，则返回$_。log()函数可以通过使用公式找到任何基数的对数：
语法： log(value)
参数：
value： 要计算对数的数字
返回：
标量背景下的浮点数
例1 :
#!/usr/bin/perl -w
# Calculating log of base 10
# using log function
print "log10(2): ", log10(2), "\n";
print "log10(7): ", log10(7), "\n";
print "log10(9): ", log10(9), "\n";
# Function for log10 calculator
sub log10
{
my n = shift;
# using pre-defined log function
return log(n) / log(10);
}
Perl
输出
log10(2): 0.301029995663981
log10(7): 0.845098040014257
log10(9): 0.954242509439325
Perl
例2:
#!/usr/bin/perl -w
# Calculating log of different
# base using log function
print "log3(2): ", log3(2), "\n";
print "log5(7): ", log5(7), "\n";
print "log2(9): ", log2(9), "\n";
# Function for log3 calculator
sub log3
{
my n = shift;
# using pre-defined log function
return log(n) / log(3);
}
# Function for log5 calculator
sub log5
{
my n = shift;
# using pre-defined log function
return log(n) / log(5);
}
# Function for log2 calculator
sub log2
{
my n = shift;
# using pre-defined log function
return log(n) / log(2);
}
Perl
输出
log3(2): 0.630929753571457
log5(7): 1.20906195512217
log2(9): 3.16992500144231
Perl