勒色的Blog

• Innovation, not instant perfection/创新不会马上就完美
  Start rough, learn and iterate./开始粗糙，学习和迭代
• Ideas come from everywhere/点子来自任何地方
  Ideas can come from the engineers, managers, users even the financial team.
• Share everything you can/分享一切
  Everything is put on the intranet, so employees know what is happening./任何事情都可以在内网分享
• You’re brilliant, we’re hiring/你有才，我雇你
  Founders Larry Page and Sergey Brin approve hires. They favor intelligence over experience. /Larry Page和Sergey Brin的雇人之道是，喜欢聪明人胜过有经验的人
• A license to pursue dreams/允许追求梦想
  Letting employees use 20% of their time on what ever they want./让员工用20%的时间做爱做的事
• Data is apolitical/数据中没有政治
  There is no “I like”, it is all about the basing decisions on data./不要说“我喜欢”，所有决定都靠数据立足
• Creativity loves constraints / 创造力爱制约
  Engineers thrive on constraints. /工程师靠限制发展
• It’s users, not money / 是用户而不是钱
  If you can successfully engage users, you can monetize them/如果你能成功吸引用户，你就能赚钱
• Don’t kill projects, morph them/不要毙掉项目，改造它
  Products that doesn’t seem to respond well in the market should be morphed into something the market needs, not cancelled /产品市场反响不好应该改造它以适应市场的需求，而不要轻易取消它

5.11练习

1. 写一个程序，类似于cat，但保持输出的顺序关系。（某些系统的名字可能是tac。）如果运行此程序：./tac fred barney betty, 输出将是文件betty 的内容，从最后一行到第一行，然后是barney, 最后是fred, 同样是从最后一行到第一行。（注意使用./确保调用的是你自己的程序，而非系统提供的）
2. 写一个程序，要求用户在不同的行中输入一些字符串，将此字符串打印出来，规则是：每一条占20 个字符宽度，右对齐。为了确保正确的输出，在开头打印出一串数字作为比较（帮助调试）。注意，不要犯19 个字符宽度的错误。例如，如果输入，hello, good-bye，则输出为：
   123456789012345678901234567890123456789012345678901234567890
                                hello
                         good-bye
3. 修改上一个程序，允许用户选择宽度，如，用户输入30，hello, good-bye(在不同的行中)，则每一行的宽度为30。（提示：参阅第二章相应部分）。提示，如果选择的宽度太长，可以增加比较行的长度。

1:
#!/usr/bin/perl -w
#Date:2009-6-18
#<Leanning Perl 4th Edition> Exercise 5-1
print reverse <>;
2-3:
#!/usr/bin/perl -w
#Date:2009-6-18
#<Leanning Perl 4th Edition> Exercise 5-2
print "What column width would you like?";
chomp (my $width = <STDIN>);
print "Enter some lines, then press Ctrl+D:\n";
chomp (my @line = <STDIN>);
print "1234567890" x (($width+9)/10), "\n";
foreach (@line) {
printf "%${width}s\n", $_;
}

4.11练习

1. 写一个名为&total 的子程序，返回一列数字的和。提示：子程序不应当有任何的I/O 操作；它处理调用的参数，返回处理后的值给调用者。结合下面的程序来练习，它检测此子程序是否正常工作。第一组数组之和我25。
   my @fred = qw{ 1 3 5 7 9 };
   my $fred_total = &total(@fred);
   print "The total of \@fred is $fred_total.\n";
   print "Enter some numbers on separate lines: ";
   my $user_total = &total(<STDIN>);
   print "The total of those numbers is $user_total.\n";
2. 利用上题的子程序，写一个程序计算从1 到1000 的数字的和。
3. 额外的练习：写一个子程序，名为&above_average，将一列数字作为其参数，返回所有大于平均值的数字（提示：另外写一个子程序来计算平均值，总和除以数字的个数）。利用下面的程序进行测试：
   my @fred = &above_average(1..10);
   print "\@fred is @fred\n";
   print "(Should be 6 7 8 9 10)\n";
   my @barney = &above_average(100, 1..10);
   print "\@barney is @barney\n";
   print "(Should be just 100)\n";

1:
#!/usr/bin/perl -w
#Date:2009-6-12
#<Leanning Perl 4th Edition> Exercise 4-1
use strict;

sub total {
    my $sum=shift @_;
    foreach (@_) {
    $sum=$sum+$_;
    }
    $sum;
}

my @fred=qw {1 3 5 7 9};
my $fred_total=&total(@fred);
print "The Total of \@fred is $fred_total.\n";

print "Enter some numbers on separate lines: ";
my $user_total = &total(<STDIN>);
print "The Total of those numbers is $user_total.\n";

2:
#!/usr/bin/perl -w
#Date:2009-6-12
#<Leanning Perl 4th Edition> Exercise 4-2
use strict;

sub total {
    my $sum=shift @_;
    foreach (@_) {
    $sum=$sum+$_;
    }
    $sum;
}

my @array=1 .. 1000;
my $array_total=&total(@array);
print "The sum of 1 to 1000 is $array_total.\n";

3:
#!/usr/bin/perl -w
#Date:2009-6-12
#<Leanning Perl 4th Edition> Exercise 4-3
use strict;

sub average {
    my $number=@_;
    my $sum=shift @_;
    foreach (@_) {
    $sum=$sum+$_;
    }
    my $array_average=$sum/$number;
}

sub above_average {
    my @above;
    foreach (@_) {
        if ($_>&average(@_)) {
        push @above,$_;
        }
    }
@above;
}

my @above_fred = &above_average(1 .. 10);
print "The above average of \@fred is @above_fred\n";

my @above_barney = &above_average(100, 1 .. 10);
print "The above average of \@barney is @above_barney\n";