珀尔 | log()函数

Perl 中的 log()函数返回传递给它的值的自然对数。如果在没有传递值的情况下调用，则返回 $_。 log()函数可用于通过使用公式找到任何碱基的对数：

Syntax: log(value)

Parameter:
value: Number of which log is to be calculated

Returns:
Floating point number in scalar context

示例 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);
}

输出：

log10(2): 0.301029995663981
log10(7): 0.845098040014257
log10(9): 0.954242509439325

示例 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);
}

输出：

log3(2): 0.630929753571457
log5(7): 1.20906195512217
log2(9): 3.16992500144231