Each programmer will, of course, have his or her own preferences in
regards to formatting, but there are some general guidelines that will
-make your programs easier to read, understand, and maintain.
+make your programs easier to read, understand, and maintain.
The most important thing is to run your programs under the B<-w>
flag at all times. You may turn it off explicitly for particular
-portions of code via the C<$^W> variable if you must. You should
-also always run under C<use strict> or know the reason why not.
-The <use sigtrap> and even <use diagnostics> pragmas may also prove
-useful.
+portions of code via the C<no warnings> pragma or the C<$^W> variable
+if you must. You should also always run under C<use strict> or know the
+reason why not. The C<use sigtrap> and even C<use diagnostics> pragmas
+may also prove useful.
Regarding aesthetics of code lay out, about the only thing Larry
-cares strongly about is that the closing curly brace of
+cares strongly about is that the closing curly bracket of
a multi-line BLOCK should line up with the keyword that started the construct.
Beyond that, he has other preferences that aren't so strong:
=item *
-Space before the opening curly of a multiline BLOCK.
+Space before the opening curly of a multi-line BLOCK.
=item *
=item *
-No space between function name and its opening paren.
+No space between function name and its opening parenthesis.
=item *
=item *
-Long lines broken after an operator (except "and" and "or").
+Long lines broken after an operator (except C<and> and C<or>).
=item *
-Space after last paren matching on current line.
+Space after last parenthesis matching on current line.
=item *
=back
-Larry has his reasons for each of these things, but he doen't claim that
+Larry has his reasons for each of these things, but he doesn't claim that
everyone else's mind works the same as his does.
Here are some other more substantive style issues to think about:
$verbose && print "Starting analysis\n";
-since the main point isn't whether the user typed B<-v> or not.
+because the main point isn't whether the user typed B<-v> or not.
Similarly, just because an operator lets you assume default arguments
doesn't mean that you have to make use of the defaults. The defaults
Even if you aren't in doubt, consider the mental welfare of the person
who has to maintain the code after you, and who will probably put
-parens in the wrong place.
+parentheses in the wrong place.
=item *
=item *
Don't be afraid to use loop labels--they're there to enhance
-readability as well as to allow multi-level loop breaks. See the
+readability as well as to allow multilevel loop breaks. See the
previous example.
=item *
+Avoid using C<grep()> (or C<map()>) or `backticks` in a void context, that is,
+when you just throw away their return values. Those functions all
+have return values, so use them. Otherwise use a C<foreach()> loop or
+the C<system()> function instead.
+
+=item *
+
For portability, when using features that may not be implemented on
every machine, test the construct in an eval to see if it fails. If
you know what version or patchlevel a particular feature was
-implemented, you can test C<$]> ($PERL_VERSION in C<English>) to see if it
+implemented, you can test C<$]> (C<$PERL_VERSION> in C<English>) to see if it
will be there. The C<Config> module will also let you interrogate values
determined by the B<Configure> program when Perl was installed.
Choose mnemonic identifiers. If you can't remember what mnemonic means,
you've got a problem.
-=item *
+=item *
-While short identifiers like $gotit are probably ok, use underscores to
-separate words. It is generally easier to read $var_names_like_this than
-$VarNamesLikeThis, especially for non-native speakers of English. It's
-also a simple rule that works consistently with VAR_NAMES_LIKE_THIS.
+While short identifiers like C<$gotit> are probably ok, use underscores to
+separate words in longer identifiers. It is generally easier to read
+C<$var_names_like_this> than C<$VarNamesLikeThis>, especially for
+non-native speakers of English. It's also a simple rule that works
+consistently with C<VAR_NAMES_LIKE_THIS>.
Package names are sometimes an exception to this rule. Perl informally
reserves lowercase module names for "pragma" modules like C<integer> and
C<strict>. Other modules should begin with a capital letter and use mixed
case, but probably without underscores due to limitations in primitive
-filesystems' representations of module names as files that must fit into a
-few sparse bites.
+file systems' representations of module names as files that must fit into a
+few sparse bytes.
=item *
-You may find it helpful to use letter case to indicate the scope
-or nature of a variable. For example:
+You may find it helpful to use letter case to indicate the scope
+or nature of a variable. For example:
- $ALL_CAPS_HERE constants only (beware clashes with perl vars!)
- $Some_Caps_Here package-wide global/static
- $no_caps_here function scope my() or local() variables
+ $ALL_CAPS_HERE constants only (beware clashes with perl vars!)
+ $Some_Caps_Here package-wide global/static
+ $no_caps_here function scope my() or local() variables
-Function and method names seem to work best as all lowercase.
-E.g., $obj->as_string().
+Function and method names seem to work best as all lowercase.
+E.g., C<$obj-E<gt>as_string()>.
You can use a leading underscore to indicate that a variable or
function should not be used outside the package that defined it.
=item *
-Use the new "and" and "or" operators to avoid having to parenthesize
-list operators so much, and to reduce the incidence of punctuational
+Use the new C<and> and C<or> operators to avoid having to parenthesize
+list operators so much, and to reduce the incidence of punctuation
operators like C<&&> and C<||>. Call your subroutines as if they were
-functions or list operators to avoid excessive ampersands and parens.
+functions or list operators to avoid excessive ampersands and parentheses.
=item *
-Use here documents instead of repeated print() statements.
+Use here documents instead of repeated C<print()> statements.
=item *
Line up corresponding things vertically, especially if it'd be too long
-to fit on one line anyway.
+to fit on one line anyway.
- $IDX = $ST_MTIME;
- $IDX = $ST_ATIME if $opt_u;
- $IDX = $ST_CTIME if $opt_c;
- $IDX = $ST_SIZE if $opt_s;
+ $IDX = $ST_MTIME;
+ $IDX = $ST_ATIME if $opt_u;
+ $IDX = $ST_CTIME if $opt_c;
+ $IDX = $ST_SIZE if $opt_s;
mkdir $tmpdir, 0700 or die "can't mkdir $tmpdir: $!";
chdir($tmpdir) or die "can't chdir $tmpdir: $!";
=item *
Always check the return codes of system calls. Good error messages should
-go to STDERR, include which program caused the problem, what the failed
-system call and arguments were, and VERY IMPORTANT) should contain the
+go to C<STDERR>, include which program caused the problem, what the failed
+system call and arguments were, and (VERY IMPORTANT) should contain the
standard system error message for what went wrong. Here's a simple but
sufficient example:
=item *
-Line up your translations when it makes sense:
+Line up your transliterations when it makes sense:
tr [abc]
[xyz];
Think about reusability. Why waste brainpower on a one-shot when you
might want to do something like it again? Consider generalizing your
code. Consider writing a module or object class. Consider making your
-code run cleanly with C<use strict> and B<-w> in effect. Consider giving away
-your code. Consider changing your whole world view. Consider... oh,
-never mind.
+code run cleanly with C<use strict> and C<use warnings> (or B<-w>) in
+effect. Consider giving away your code. Consider changing your whole
+world view. Consider... oh, never mind.
+
+=item *
+
+Try to document your code and use Pod formatting in a consistent way. Here
+are commonly expected conventions:
+
+=over 4
+
+=item *
+
+use C<CE<lt>E<gt>> for function, variable and module names (and more
+generally anything that can be considered part of code, like filehandles
+or specific values). Note that function names are considered more readable
+with parentheses after their name, that is C<function()>.
+
+=item *
+
+use C<BE<lt>E<gt>> for commands names like B<cat> or B<grep>.
+
+=item *
+
+use C<FE<lt>E<gt>> or C<CE<lt>E<gt>> for file names. C<FE<lt>E<gt>> should
+be the only Pod code for file names, but as most Pod formatters render it
+as italic, Unix and Windows paths with their slashes and backslashes may
+be less readable, and better rendered with C<CE<lt>E<gt>>.
+
+=back
=item *
https://perl5.git.perl.org / perl5.git / blobdiff