Perl 简明教程
Perl - Data Types
Perl 是一种松散类型的语言，在程序中使用数据时无需指定类型的类型。Perl 解释器将根据数据本身的上下文选择类型。
Perl is a loosely typed language and there is no need to specify a type for your data while using in your program. The Perl interpreter will choose the type based on the context of the data itself.
Perl 有三种基本数据类型：标量、标量的数组和标量的散列，也称为关联数组。以下是对这些数据类型的简要说明。
Perl has three basic data types: scalars, arrays of scalars, and hashes of scalars, also known as associative arrays. Here is a little detail about these data types.
Sr.No. |
Types & Description |
1 |
Scalar Scalars are simple variables. They are preceded by a dollar sign ($). A scalar is either a number, a string, or a reference. A reference is actually an address of a variable, which we will see in the upcoming chapters. |
2 |
Arrays Arrays are ordered lists of scalars that you access with a numeric index, which starts with 0. They are preceded by an "at" sign (@). |
3 |
Hashes Hashes are unordered sets of key/value pairs that you access using the keys as subscripts. They are preceded by a percent sign (%). |
Numeric Literals
Perl 在内部将所有数字存储为有符号整数或双精度浮点值。数字文本使用以下浮点或整数格式中的任何一种指定 −
Perl stores all the numbers internally as either signed integers or double-precision floating-point values. Numeric literals are specified in any of the following floating-point or integer formats −
Type |
Value |
Integer |
1234 |
Negative integer |
-100 |
Floating point |
2000 |
Scientific notation |
16.12E14 |
Hexadecimal |
0xffff |
Octal |
0577 |
String Literals
字符串是由字符序列构成的。它们通常是使用单引号 (') 或双引号 (") 分隔的字母数字值。它们与 UNIX shell 引号类似，您可以在其中使用单引号字符串和双引号字符串。
Strings are sequences of characters. They are usually alphanumeric values delimited by either single (') or double (") quotes. They work much like UNIX shell quotes where you can use single quoted strings and double quoted strings.
双引号字符串文本允许变量插值，而单引号字符串则不行。某些字符在反斜杠前面时具有特殊含义，并且用于表示换行符 (\n) 或制表符 (\t)。
Double-quoted string literals allow variable interpolation, and single-quoted strings are not. There are certain characters when they are proceeded by a back slash, have special meaning and they are used to represent like newline (\n) or tab (\t).
您可以在双引号字符串中直接嵌入换行符或以下任何转义序列−
You can embed newlines or any of the following Escape sequences directly in your double quoted strings −
Escape sequence |
Meaning |
|Backslash |
\' |
Single quote |
\" |
Double quote |
\a |
Alert or bell |
\b |
Backspace |
\f |
Form feed |
\n |
Newline |
\r |
Carriage return |
\t |
Horizontal tab |
\v |
Vertical tab |
\0nn |
Creates Octal formatted numbers |
\xnn |
Creates Hexideciamal formatted numbers |
\cX |
Controls characters, x may be any character |
\u |
Forces next character to uppercase |
\l |
Forces next character to lowercase |
\U |
Forces all following characters to uppercase |
\L |
Forces all following characters to lowercase |
\Q |
Backslash all following non-alphanumeric characters |
\E |
Example
让我们再来看看字符串在单引号和双引号下的行为方式。这里，我们将使用上表中提到的字符串转义，并将利用标量变量分配字符串值。
Let’s see again how strings behave with single quotation and double quotation. Here we will use string escapes mentioned in the above table and will make use of the scalar variable to assign string values.
#!/usr/bin/perl
# This is case of interpolation.
$str = "Welcome to \ntutorialspoint.com!";
print "$str\n";
# This is case of non-interpolation.
$str = 'Welcome to \ntutorialspoint.com!';
print "$str\n";
# Only W will become upper case.
$str = "\uwelcome to tutorialspoint.com!";
print "$str\n";
# Whole line will become capital.
$str = "\UWelcome to tutorialspoint.com!";
print "$str\n";
# A portion of line will become capital.
$str = "Welcome to \Ututorialspoint\E.com!";
print "$str\n";
# Backsalash non alpha-numeric including spaces.
$str = "\QWelcome to tutorialspoint's family";
print "$str\n";这会产生以下结果 −
This will produce the following result −
Welcome to
tutorialspoint.com!
Welcome to \ntutorialspoint.com!
Welcome to tutorialspoint.com!
WELCOME TO TUTORIALSPOINT.COM!
Welcome to TUTORIALSPOINT.com!
Welcome\ to\ tutorialspoint\'s\ family