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authorGuillaume Cottenceau <gc@mandriva.com>2003-04-30 22:38:35 +0000
committerGuillaume Cottenceau <gc@mandriva.com>2003-04-30 22:38:35 +0000
commitb1f265fec66a76739369eeff9c0c7edd8539ea40 (patch)
treea249e984ac9475238008ed768a9e88c4f9da543a
parent400fd9e4484030a7c9605ea800f1ac963f52328a (diff)
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talking bout perl_checker
-rw-r--r--tutorial.html141
1 files changed, 121 insertions, 20 deletions
diff --git a/tutorial.html b/tutorial.html
index 841472f..3db5d42 100644
--- a/tutorial.html
+++ b/tutorial.html
@@ -45,9 +45,9 @@
<p>Thanks to <tt>perl-MDK-Common</tt>'s own documentation, an
easy way to directly access information about the provided
- functions, you can use <tt>perldoc</tt>, for example
- <tt>perldoc MDK::Common::Func</tt> will explain the functions
- of the Func module. Use <tt>perldoc MDK::Common</tt> to view
+ functions is to use <tt>perldoc</tt>. For example,
+ <tt>perldoc MDK::Common::Func</tt> will list the functions
+ of the Func sub-module. Use <tt>perldoc MDK::Common</tt> to view
information on all the available functions.</p>
<p>Additionally, <tt>perl-MDK-Common</tt> provides a binary
@@ -64,7 +64,7 @@
<p>Of course, a first look at the Perl language will be
necessary for the reader. The following can be a good Perl
- Tutorial (though there are many of them on the web): <a
+ Tutorial (although there are many others on the web): <a
href="http://www.comp.leeds.ac.uk/Perl/">http://www.comp.leeds.ac.uk/Perl/</a>.</p>
<p>Programming with <tt>perl-MDK-Common</tt> also emphasizes
@@ -84,7 +84,7 @@
common technique among programmers, and maybe it's even worse
with Perl programmers; but functional-style programs are often
clearer, more expressive, more reusable, and more
- maintainable</li>
+ maintainable, than traditional programs</li>
<br>
<li><b>strict code style:</b> Perl is known to be a language
@@ -125,13 +125,13 @@
<p><b>Note:</b> many functions' name, extending capabilities of
existing functions, or being their functional counterpart, are
suffixed with the underscore character (<tt>_</tt>); for
- example, <tt>chomp_</tt> is the equivalent of <tt>chomp</tt>,
- but returns the chomp'ed results instead of modifying its
- argument.</p>
+ example, <tt>chomp_</tt> is the semantical equivalent of
+ <tt>chomp</tt>, but returns the chomp'ed results instead of
+ modifying its argument.</p>
<ul>
<li>
- <b>cat_</b>(FILENAME): returns the file contents: in scalar
+ <b>cat_</b>(FILENAME): returns the file contents; in scalar
context it returns a single string, in array context it
returns the lines. If the file doesn't exist, it returns
<tt>undef</tt>.
@@ -156,14 +156,12 @@
<b>output</b>(FILENAME, LIST): creates a file and outputs the
list (if the file exists, it is clobbered)
- <p>Counterpart of <tt>cat_</tt>. Build the contents of the file
- in your program, and when you're happy with it, write it on
- disk:</p>
+ <p>Counterpart of <tt>cat_</tt>:</p>
<pre class="SCREEN">
- my @resolv_conf = qw(search mandrakesoft.com);
- push @resolv_conf, "nameserver $_" foreach @name_servers;
- output('/etc/resolv.conf', @resolv_conf);
+ output('/tmp/resolv.conf',
+ "search $domain\n",
+ map { "nameserver $_\n" } @name_servers);
</pre>
</li>
@@ -276,7 +274,7 @@
# equivalent (but much more elegant!) to:
- my @md_devices = map { /^(md\d+)/; $1 } grep { /^md\d+/ } cat_('/proc/mdstat');
+ my @md_devices = map { /^(md\d+)/ } grep { /^md\d+/ } cat_('/proc/mdstat');
</pre>
</li>
@@ -294,8 +292,9 @@
<li>
- <b>each_index</b> { CODE } LIST: just like <tt>each</tt>, but
- sets $::i
+ <b>each_index</b> { CODE } LIST: iterate on a list to execute
+ some code needing the index of the list element (available in
+ <tt>$::i</tt>)
<p>Useful when you need to perform an action on each element of
a list, but you also need the index of each element:</p>
@@ -313,13 +312,115 @@
<h2>perl_checker</h2>
- <p></p>
+ <p>Let's examine now the code-style perl_checker wants you to
+ adopt. Let's consider the following naive code example:</p>
+ <pre class="SCREEN">
+ 1: sub calc {
+ 2: my ($x,$y) = @_;
+ 3: $_ = $y;
+ 4: ($x==0 && $y==0) and return -1;
+ 5: my @tab = (1, 2, 3);
+ 6:
+ 7: /sysconfig\/i18n/ and return 1;
+ 8: }
+ </pre>
+
+ <p>
+ The following problems are reported:
+ </p>
+
+ <ul>
+ <li><pre class="SCREEN">
+line 2, character 12-12
+you should have a space here</pre>
+
+ <p>
+ Good: <tt>my ($x, $y) = @_;</tt>
+ <br>
+ Why: you should put a space after the comma when specifying a list.
+ </p>
+
+ <li><pre class="SCREEN">
+line 3, character 5-7
+undeclared variable $_</pre>
+
+ <p>
+ Good: <tt>local $_ = $y;</tt>
+ <br>
+ Why: you should always localize <tt>$_</tt> when you set it, because it's a global variable.
+ </p>
+
+ <li><pre class="SCREEN">
+line 4, character 8-8
+you should have a space here</pre>
+
+ <p>
+ Good: <tt>($x == 0 && $y == 0) and return -1;</tt>
+ <br>
+ Why: you should put spaces before and after operators.
+ </p>
+
+ <li><pre class="SCREEN">
+line 4, character 5-21
+unneeded parentheses</pre>
+
+ <p>
+ Good: <tt>$x == 0 && $y == 0 and return -1;</tt>
+ <br>
+ Why: because of operators precedence, the parentheses are unneeded (if unsure about precedence, see <tt>perlop(1)</tt>)
+ </p>
+
+ <li><pre class="SCREEN">
+line 5, character 8-12
+unused variable @tab</pre>
+
+ <p>
+ Why: Assigning to unused variables is (typically) useless. If you really need to assign to an unused variable, prefix its name with `_' and perl_checker will stop boring you (for example, <tt>@_tab</tt>).
+ </p>
+
+ <li><pre class="SCREEN">
+line 7, character 20-21
+change the delimit character / to get rid of this escape</pre>
+
+ <p>
+ Good: <tt>m|sysconfig/i18n|</tt>
+ <br>
+ Why: <tt>/</tt> is not the only regexp delimiter! if you want to specify a slash in your regexp, use another delimiter so that your regexp will be more readable.
+ </p>
+
+ </ul>
+
+ <p>Finally, the correct code looks like:</p>
+
+ <pre class="SCREEN">
+ sub calc {
+ my ($x, $y) = @_;
+ local $_ = $y;
+ $x == 0 && $y == 0 and return -1;
+ my @_tab = (1, 2, 3);
+
+ m|sysconfig/i18n| and return 1;
+ }
+ </pre>
+
+ <p>Under Emacs, you might want to add the following to your
+ <tt>.emacs</tt> and then be able to validate your code with <tt>C-Enter</tt>:</p>
+ </p>
+
+ <pre class="SCREEN">
+ (defmacro ilam (&rest body) `(lambda () (interactive) ,@body))
+ (add-hook 'cperl-mode-hook
+ '(lambda ()
+ (local-set-key [(control return)]
+ (ilam (save-some-buffers 1) (compile (concat "perl_checker --restrict-to-files " (buffer-file-name (current-buffer))))))
+ ))
+ </pre>
<hr />
<p>
- Last update: Fri Apr 18 22:08:06 2003
+ Last update: Wed Apr 30 18:05:40 2003
</p>
</body>