The map function of Perl

Source:

Use of the map function of Perl:

Grammar

Map EXPR, LIST of which there is,

Map BLOCK LIST None of this,

Define and use

Executes expr or block on each element in the list, returning a new list. For each of these iterations, the values of the elements of the current iteration are saved in $_.

return value

If the return value is stored in a scalar scalar, the number of elements in the array is returned on behalf of Map ();

If the return value is stored in the list, it represents an array of map () functions;

Example 1 (Capitalize the first letter of the word)

 
 
 1 Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->#!/usr/bin/perl -w
 2 
 3 @myNames = (‘jacob‘, ‘alexander‘, ‘ethan‘, ‘andrew‘);
 4 @ucNames = map(ucfirst, @myNames);
 5 $numofucNames = map(ucfirst, @myNames);
 6 
 7 foreach $key ( @ucNames ){
 8  print "$key\n";
 9 }
10 print $numofucNames;

Result is

 
Jacob
Alexander
Ethan
Andrew
4

Example 2 (get all the words contained in the title and convert to uppercase)

 
 
1 my@books = (‘Prideand Prejudice‘,‘Emma‘, ‘Masfield Park‘,‘Senseand Sensibility‘,‘Nothanger Abbey‘,
2 ‘Persuasion‘,  ‘Lady Susan‘,‘Sanditon‘,‘The Watsons‘);
3 
4 my@words = map{split(/\s+/,$_)}@books;
5 my@uppercases = map uc,@words;
6 foreach $upword ( @uppercases ){
7  print "$upword\n";
8 }

The result is (the input array and the output array of the Perl map function are not necessarily long, and after the split has worked, of course the length of the @words is longer than the @books.) ）

 
PRIDEAND
PREJUDICE
EMMA
MASFIELD
PARK
SENSEAND
SENSIBILITY
NOTHANGER
ABBEY
PERSUASION
LADY
SUSAN
SANDITON
THE

Example 3 (extract the extra 2 digits to the new list)

 
1 my @buildnums = (‘R010‘,‘T230‘,‘W11‘,‘F56‘,‘dd1‘);
2 my @nums = map{/(\d{2,})/} @buildnums;
3 foreach $num (@nums){
4   print "$num \n"
5 }

Results

 
010 
230 
11 
56 

Instance 4 matches the scalar and list context return values

 
 1 $a = ‘RRR32Sttt‘;
 2 @yy = $a=~/RRR.*ttt/;
 3 $numofyy = $a=~/RRR.*ttt/;
 4 print "@yy\n";
 5 print "$numofyy\n" ;
 6 print "$1";
 7 
 8 @yy2 = $a=~/(RRR).*(ttt)/;
 9 $numofyy2 = $a=~/(RRR).*(ttt)/;
10 print "@yy2\n";
11 print "$numofyy2\n";
12 print "$1 $2";

Result (the array or length returned after a regular expression match depends on whether or not the expression has () or the type of variable received)

 
1
1
RRR ttt
1
RRR ttt

whether there is a () variable type result received in an expression

No scalar forever 1 or 0

There are scalars forever 1 or 0

No list forever (1 or 0)

List with List of results

Perl's Map function