Perl getting started (array)

 

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Array variables start with the character "@"

@ Array = (1, 2, 3 );

@ Var = (11, 27.1, "a string ");

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Copy between Arrays

@ Result = @ original;

 

Assign values to the list using Arrays

@ List1 = (2, 3, 4 );

@ List2 = (1, @ list1, 5); # @ list2 = (1, 2, 3, 4, 5)

 

Array assignment to simple variables

@ Array = (5, 7, 11 );

($ Var1, $ var2) = @ array; # $ var1 = 5, $ var2 = 7, 11 ignored

 

@ Array = (5, 7 );

($ Var1, $ var2, $ var3) = @ array; # $ var1 = 5, $ var2 = 7, $ var3 = "" (null)

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Assign values to variables from standard input (stdin)

$ Var = <stdin>;

@ Array = <stdin>; # ^ d indicates the end input symbol.

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List range:

(1 .. 10) = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

(2, 5 .. 7, 11) = (2, 5, 6, 7, 11)

(3 .. 3) = (3)

Used for real numbers

(5.3. 2.1) = (3.1, 4.1, 5.1)

(1.6) = ()

Used as a string

("AAA"... "aad") = ("AAA", "AAB", "AAC", "aad ")

@ Day_of_month = ("01" .. "31 ")

Can contain variables or expressions

($ Var1.. $ var2 + 5)

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Array output:

@ Array = (1, 2, 3 );

Print (@ array, "/N ");

Result:

123

@ Array = (1, 2, 3 );

Print ("@ array/N ");

Result:

1 2 3

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Length of list/Array

When the array variable appears where the expected simple variable appears, the perl interpreter takes its length.

@ Array = (1, 2, 3 );

$ Scalar = @ array; # $ scalar = 3, that is, the length of @ Array

($ Scalar) = @ array; # $ scalar = 1, that is, the value of the first element of @ Array

Note: You can program the number of cycles based on the length of the array as follows:

$ COUNT = 1;

While ($ count <= @ array ){

Print ("element $ count: $ array [$ count-1]/n ");

$ Count ++;

}

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Child Array

@ Array = (1, 2, 3, 4, 5 );

@ Subarray = @ array [0, 1]; # @ subarray = (1, 2)

@ Subarray2 = @ array [1 .. 3]; # @ subarray2 = (2, 3, 4)

@ Array [] = ("string", 46); # @ array = ("string",) now

@ Array [0 .. 3] = (11, 22, 33, 44); # @ array = (11,22, 33,44, 5) now

@ Array [, 3] = @ array [, 4]; # @ array = (, 5, 5) now

@ Array [0 .. 2] = @ array [3, 4]; # @ array = (5, 5, "", 5, 5) now

Elements can be exchanged in the form of subarrays:

@ Array [1, 2] = @ array [2, 1];

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7. database functions related to Arrays

(1) sort -- sort by character

@ Array = ("this", "is", "A", "test ");

@ Array2 = sort (@ array); # @ array2 = ("A", "is", "test", "this ")

@ Array = (70,100, 8 );

@ Array = sort (@ array); # @ array = (100, 70, 8) now

(2) reverse -- reverse an array

@ Array2 = reverse (@ array );

@ Array2 = reverse sort (@ array );

(3) chop -- remove the array from the tail

The significance of chop is to remove the last character-line break when stdin (keyboard) is entered. If it is applied to an array, it will process every element in the array.

@ List = ("rabbit", "12345", "quartz ");

Chop (@ list); # @ list = ("Rabbi", "1234", "quart") now

(4) join/split -- join/split

The first parameter of join is the intermediate character used for the connection, and the rest is the character array to be connected.

$ String = join ("", "this", "is", "A", "string"); # The result is "this is a string"

@ List = ("Words", "and ");

$ String = join (":", @ list, "colons"); # The result is "Words: And: colons"

@ Array = Split (/: //, $ string); # @ array = ("Words", "and", "colons") now

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$ COUNT = 1; <br/> @ array = ("my", "name", "is", "wangbichao "); <br/> while ($ count <= @ array) <br/>{< br/> Print ("element $ count: $ array [$ count-1]/n "); <br/> $ count ++; <br/>}</P> <p> $ COUNT = 1; <br/> @ array = sort (@ array); # sort by character <br/> while ($ count <= @ array) <br/>{< br/> Print ("element $ count: $ array [$ count-1]/n"); <br/> $ count ++; <br/>}</P> <p> $ COUNT = 1; <br/> @ array = reverse (@ array ); # Reverse array <br/> while ($ count <= @ array) <br/> {<br/> Print ("element $ count: $ array [$ count-1]/n "); <br/> $ count ++; <br/>}</P> <p> $ COUNT = 1; <br/> chop (@ array); # remove each scalar in the array from the end <br/> # @ array = chop (@ array); this write cannot be output, I don't know why! <Br/> while ($ count <= @ array) <br/>{< br/> Print ("element $ count: $ array [$ count-1]/n "); <br/> $ count ++; <br/>}</P> <p> $ COUNT = 1; <br/> $ string = join ("---", @ array); # The first parameter of join is the intermediate character used for the connection, and the rest is the character array to be connected. <Br/> Print ("$ string/N"); <br/> while ($ count <= @ array) <br/>{< br/> Print ("element $ count: $ array [$ count-1]/n"); <br/> $ count ++; <br/>}</P> <p> Print ("$ string/N"); <br/> @ array = Split (/---/, $ string ); # Remove the part containing "---" in a string and split it into an array <br/> Print ("@ array", "/N "); <br/> $ COUNT = 1; <br/> while ($ count <= @ array) <br/>{< br/> Print ("elemrnt $ count: $ array [$ count-1]/n "); <br/> $ count ++; <br/>}