Re^3: a simple exercise in readability

First of all, apotheon, that's a very nice syntax message. So many times, when I've run a script or program which gave no clue as to its purpose, I've wished for a syntax message even 1/10th as good as that one, so kudos for writing something clear and descriptive!

Secondly, instead of:

HELP_MESSAGE() and exit unless $ARGV[1];
foreach (@ARGV) {
  HELP_MESSAGE() and exit unless /^-?\d+$/
} 

# ... and later ...
sub HELP_MESSAGE {
  print $help;
}
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why not just do the following, which is (I think) more clear, takes less space, and is more precise in the case of invalid input ...

die $help unless $ARGV[1];
map { /^-?\d+$/ or die "Invalid input $_\n" } @ARGV;
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s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/

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Re^4: a simple exercise in readability
by apotheon (Deacon) on Jan 15, 2007 at 15:40 UTC

Thanks for the compliments on my help message text. I do try to be clear.

You may have a point, re: your replacement code, with the exception that eliminating the subroutine definition for HELP_MESSAGE() would cause the script to fail to produce the contents of $help when invoked with the --help option. Thus, my two explicit conditional invocations of HELP_MESSAGE() should probably be replaced as you indicated, though I'd keep the subroutine. New code:

die $help unless $ARGV[1];
map { /^-?\d+$/ or die "Invalid input $_\n" } @ARGV;

# . . . and later . . .
sub HELP_MESSAGE {
  print $help;
}
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If I don't keep that subroutine in there, the --help option causes the following output to be produced:

/home/ren/bin/ies version 1.0 calling Getopt::Std::getopts (version 1.
+05),
running under Perl version 5.8.8.


Usage: series [-OPTIONS [-MORE_OPTIONS]] [--] [PROGRAM_ARG1 ...]


The following single-character options are accepted:
        Boolean (without arguments): -s

Options may be merged together.  -- stops processing of options.
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edit: johngg pointed out the "unless" bug above, where unless @ARGV should read unless defined @ARGV instead.

print substr("Just another Perl hacker", 0, -2);
- apotheon
CopyWrite Chad Perrin

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Re^5: a simple exercise in readability

by johngg (Canon) on Jan 15, 2007 at 16:57 UTC

die $help unless $ARGV[1];
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and it's previous incarnations will die erroneously if the user wants to sum from, say, -7 to 0. Perhaps unless defined $ARGV[1]; would be better?

Cheers,

JohnGG

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Re^6: a simple exercise in readability

by apotheon (Deacon) on Jan 15, 2007 at 17:08 UTC

Good catch. Thanks -- I've edited the code on my system at home, though I'll leave the error as it is where you noticed it here at PerlMonks.

print substr("Just another Perl hacker", 0, -2);
- apotheon
CopyWrite Chad Perrin

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