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Perl log()用法及代码示例

Perl中的log()函数返回传递给它的值的自然对数。如果调用时未传递值,则返回$_。 log()函数可用于使用以下公式查找任何底数的对数:

用法: log(value)

参数:
value:要计算的日志数


返回:
标量上下文中的浮点数

范例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


范例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


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注:本文由纯净天空筛选整理自Code_Mech大神的英文原创作品 Perl | log() Function。非经特殊声明,原始代码版权归原作者所有,本译文的传播和使用请遵循“署名-相同方式共享 4.0 国际 (CC BY-SA 4.0)”协议。