练习册第15章习题

15.1. [Perl 5.10.1] Use the smart match operator in a program that prompts the user
for a string and reports if that string is an element of an array you specify in your
program. You only have to match exact elements.

use 5.016;
my @array = qw(Fred Wilma Barney Betty Larry Pebbles Bamm-Bamm);
say "The elements are (@array)";
say "Enter a name:";

chomp(my $name=<STDIN>);

given($name) {

    when ($name ~~ @array) {say "I found a matching name"}
    default {say "I didn't find a matching name"}

}

 

15.2. [Perl 5.10.1] Modify your answer to Exercise 15.1 to prompt the user to enter
several names, one line per name. Report success if at least one of the names is a key
in a hash that you define in your program.

use 5.016;
my %hash = qw(
Fred Flintstone
Wilma Flintstone
Barney Rubble
Betty Rubble
Larry Slate
Pebbles Flintstone
Bamm-Bamm Rubble
);

say "The keys:[",(join ' ',keys %hash),"]";
say "Enter some names then Control-Z to stop:";

chomp (my @inputs=<STDIN>) ;

if (@inputs ~~ %hash) {
    say 'I found a matching name';
}else {
    say "I didn't find a matching name";
}

 

15.3. [Perl 5.10.1] Write a program that prompts the user for a regular expression
pattern and reports if any elements of an array match that pattern. Use the smart match
operator to check if that pattern matches. You don’t need to report which elements
match. As a bonus, what do you do if the user enters an invalid regular expression

use 5.016;
my @array = qw(Fred Wilma Barney Betty Larry Pebbles Bamm-Bamm);
say "The elements are (@array)";
say "Enter a pattern:";
chomp(my $reg=<STDIN>);

if ( eval{ /$reg/ ~~ @array} ) {
    say "At least one element matches";
}else {
    say "No element matches";
}

if ($@) {
    say "error:$@";
}

 

15.4. [Perl 5.10.1] Write a program that prompts you for two lists of words. Use the
smart match operator to report if these two lists are the same or not. To make things
easier, enter each list on a single line then split that line on whitespace.

use 5.016;
say "Enter the first list on a single line:";
my @first = split /\s+/,<STDIN> ;


say "Enter the second list on a single line:";
my @second = split /\s+/,<STDIN> ;

if (@first ~~ @second) {
    say 'The lists are the same'; 
}else {
    say 'The lists are not the same';
}

 

15.5. [Perl 5.10.1] Use given-when and smart matching to implement a word guessing
game. If the user enters a string that exactly matches the secret word, report success.
If the string doesn’t match, try that string as a regular expression pattern. If the user
enters give up, stop the program (and, if you want to be nice, tell them the secret word).

#!/usr/bin/perl
# 第15章 练习册 课后习题5
use 5.016;

my $Verbose = $ENV{VERBOSE} // 1 ;
my $secret = "david";

print 'Enter a string or pattern>';

while (1) {
    chomp(my $guess=<STDIN>);
    given($guess){
        when('give up') {
            say 'Too hard? Better luck next time!';
            last ;
        }

        when($secret){
            say 'You gueesed the secret word!';
            last;


        }

        when( $secret ~~ /$_/){
            say "The secret word matcheds the pattern [$guess]";
            print '\nEnter another string or pattern>';

        }

        default {
            say "[$guess] did not help at all!";
            print '\nEnter another string or pattern>';

        }


        


    }
}