Perl |布尔值
在大多数编程语言中，真和假被认为是布尔值。但是 Perl 没有为“真”和“假”提供布尔类型。一般来说，当函数返回真或假时，程序员可以使用术语“布尔”。像条件语句(if，while 等。)将为标量值返回 true 或 false。
例:
Perl
# Perl Code to demonstrate the boolean values
# variable assigned value 0
$k = 0;
# checking whether k is true or false
if ($k)
{
print "k is True\n";
}
else
{
print "k is False\n";
}
# variable assigned value 2
$m = 2;
# checking whether m is true or false
if ($m)
{
print "m is True\n";
}
else
{
print "m is False\n";
}
输出:
k is False
m is True
真值:在 Perl 语言中，除零之外的任何非零数字都是真值。字符串常量，如“真”、“假”、“”(以空格为字符的字符串)、“00”(2 个或更多个 0 字符)和“0 \ n”(字符串中的一个零后跟一个换行符)等。还要考虑 Perl 中的真值。
- Example:
Perl
# Perl Code to demonstrate the True values
# variable assigned value 5
$a = 5;
# checking whether a is true or false
if ($a)
{
print "a is True\n";
}
else
{
print "a is False\n";
}
# string variable assigned white
# space character
$b = ' ';
# checking whether b is true or false
if ($b)
{
print "b is True\n";
}
else
{
print "b is False\n";
}
# string variable assigned 'false'
# value to it
$c = 'false';
# checking whether c is true or false
if ($c)
{
print "c is True\n";
}
else
{
print "c is False\n";
}
# string variable assigned "0\n"
# value to it
$d = "0\n";
# checking whether d is true or false
if ($d)
{
print "d is True\n";
}
else
{
print "d is False\n";
}
输出:
a is True
b is True
c is True
d is True
假值: 空字符串或 s 字符串包含单个数字 0 或unde值和零被认为是 perl 中的假值。
- Example:
Perl
# Perl Code to demonstrate the False values
# variable assigned value 0
$a = 0;
# checking whether a is true or false
if ($a)
{
print "a is True\n";
}
else
{
print "a is False\n";
}
# string variable assigned empty string
$b = '';
# checking whether b is true or false
if ($b)
{
print "b is True\n";
}
else
{
print "b is False\n";
}
# string variable assigned undef
$c = undef;
# checking whether c is true or false
if ($c)
{
print "c is True\n";
}
else
{
print "c is False\n";
}
# string variable assigned ""
# value to it
$d = "";
# checking whether d is true or false
if ($d)
{
print "d is True\n";
}
else
{
print "d is False\n";
}
输出:
a is False
b is False
c is False
d is False
注意:对于用户必须比较两个不同变量的条件检查，如果它们不相等，则返回假否则返回真。
- Example:
Perl
# Perl Program demonstrate the conditional check
# variable initialized with string
$x = "GFG";
# using if statement
if ($x eq "GFG")
{
print "Return True\n";
}
else
{
print "Return False\n";
}
输出:
Return True
