Learning Perl chapter 4 练习题

原文发表在网易博客 2010-11-06 13:07:36

第1题和第2题

#!perl -w
#chapter 4 , exercise one and two
use strict;
sub total{
    my $sum;
    foreach $_ (@_){
        $sum += $_;
        }
        $sum;
    }
my @fred=(1,3,5,7,9);
print "sum of (@fred) is:\t ",&total(@fred),"\n";

print "sum of 1 to 100 is :\t",&total(1..100),"\n";

第3题

#!perl -w
#chapter 4 , exercise 3
use strict;
sub getSum{
    my $sum=0;
    foreach $_ (@_){
        $sum+=$_;
        }
    $sum;
    }
sub getAverage{
    my @abovelist=();
    my $length=@_;
    my $average=-1;
    $average=&getSum(@_)/$length;
    }
sub above_average{
    my @abovelist;
    my $average=&getAverage(@_);
    foreach $_ (@_){
        if($_ > $average){
            push @abovelist, $_
            }
        }
    return @abovelist;
    }
my @fred=&above_average(1..10);
print "above the average in one to ten is :(@fred)\n";

第4题

#!perl -w
use strict;
use 5.010;
sub greet1{
    state $lastPerson="";
    if(@_ ==1 ){
        if($lastPerson ne ""){
            print "Hi,$_[0]!$lastPerson is also here.\n";
            }else{
                print "Hi,$_[0]!You are the first one here!\n";
                }
        $lastPerson=$_[0];
        }
    }
&greet1("leipei");
&greet1("ada");

第5题

#!perl -w
use strict;
use 5.010;
sub greet2{
    state @personlist;
    if(@_ == 1){
        if(@personlist >0){
            print "Hi,$_[0]! I have seen:@personlist\n";
            }else{
                print "Hi,$_[0]! You are the firt one here.\n";
                }
        push (@personlist,$_[0]);
        }
    }
greet2("Fred");
greet2("Barney");
greet2("Wilma");
greet2("Betty");