4 ms·

This deprecation affects things like $\cT, where \cT is a literal control (such as a NAK or NEGATIVE ACKNOWLEDGE character) in the source code. Sur

by DHowett 12y ago

This deprecation affects things like $\cT, where \cT is a literal control (such as a NAK or NEGATIVE ACKNOWLEDGE character) in the source code. Surprisingly, it appears that originally this was intended as the canonical way of accessing variables like $^T, with the caret form only being added as an alternative. I love perl and use it nigh-unto daily, but—what could possibly have been the thought process behind that? A literal control character?

deckiedan 12y ago
writing scripts that control programs (such as SSH, emacs, nano, etc) that expect a keyboard and TTY to be controlling them?
- VLM 12y ago
  That's actually a stereotypical bug, doesn't work that way. http://perldoc.perl.org/perlvar.html http://perldoc.perl.org/perlvar.html If you try to use and output ^O while thinking you're outputting a literal control-O then you'll be in for a big surprise. The language allows (length) 250 or so character variable names with few restrictions, so using single character names is probably a bug or at least bad style, so when the devs are looking for a class of global "internal-ish" variable names, how about those icky single character names that no one should be using? So that's how you end up with $^V being aliased to a string representation of the version of perl interpreter currently executing. You really shouldn't be using single character variable names so they've been repurposed and attempting to re-re-purpose them might be very exciting.
bkeroack 12y ago
As someone with zero Perl experience...is this a joke? People naming variables with literal control characters?!
- VLM 12y ago
  Yes. Its a running joke WRT general global variables, and they all have a single character synonym. And once you use up the preferred letters, well, stranger things are used. a C programmer who understands command line argument lists would not even remotely be surprised at the contents of the general variable $0. Its probably more "civilized" to call it $PROGRAM_NAME in your code, but whatever. I don't think this is controversial to alias $PROGRAM_NAME to $0 for anyone civilized aka some minimal C experience. Perl tends to be consistent. In a similar style, if you insist on implementing a global general variable like $PERL_VERSION which contains a string of pretty much what it sounds like it contains, to keep things consistent all general vars also have a single character synonym, so welcome to $"control-V" In the "real world" you can write something stupid enough to get yourself fired. This kind of activity probably qualifies unless you have an excellent excuse. Perhaps if you have a complicated if-then statement with numerous clauses and using one individual weird, yet short, variable name allows a debugging programmer to keep the whole control flow in their head instead of scrolling the mess off the screen, then, maybe, its a win. But I wouldn't make a habit of it. Given that you can pretty much transparently "upgrade" or "downgrade" the code with a simple search and replace its not a major crisis. A lot of people use Perl::Critic as a Perl "lint" and a lot of those users put large amounts of the perlvars file in the Variables::ProhibitEvilVariables test although the Perl::Critic authors don't by default include them, which many people consider a bug in Perl::Critic but whatever.
  - gpvos 12y ago
    > Perl tends to be consistent. Well, for a certain kind of consistency, yes. From the perlfunc manpage, about the return values of Perl's operators and functions in scalar versus list context: In general, they do what you want, unless you want consistency.
  - Mithaldu 12y ago
    > Its probably more "civilized" to call it $PROGRAM_NAME in your code, but whatever. I don't think this is controversial to alias $PROGRAM_NAME to $0 for anyone civilized aka some minimal C experience. There is `use English;` for that. :)
  - pflanze 12y ago
emmelaich 12y ago
Could be worse! "Why does Java allow control characters in its identifiers?" http://stackoverflow.com/questions/4838507/why-does-java-allow-control-characters-in-its-identifiers http://stackoverflow.com/questions/4838507/why-does-java-all...

by DHowett 12y ago

deckiedan 12y ago

writing scripts that control programs (such as SSH, emacs, nano, etc) that expect a keyboard and TTY to be controlling them?

VLM 12y ago
That's actually a stereotypical bug, doesn't work that way. http://perldoc.perl.org/perlvar.html http://perldoc.perl.org/perlvar.html If you try to use and output ^O while thinking you're outputting a literal control-O then you'll be in for a big surprise. The language allows (length) 250 or so character variable names with few restrictions, so using single character names is probably a bug or at least bad style, so when the devs are looking for a class of global "internal-ish" variable names, how about those icky single character names that no one should be using? So that's how you end up with $^V being aliased to a string representation of the version of perl interpreter currently executing. You really shouldn't be using single character variable names so they've been repurposed and attempting to re-re-purpose them might be very exciting.

bkeroack 12y ago

As someone with zero Perl experience...is this a joke? People naming variables with literal control characters?!

VLM 12y ago
Yes. Its a running joke WRT general global variables, and they all have a single character synonym. And once you use up the preferred letters, well, stranger things are used. a C programmer who understands command line argument lists would not even remotely be surprised at the contents of the general variable $0. Its probably more "civilized" to call it $PROGRAM_NAME in your code, but whatever. I don't think this is controversial to alias $PROGRAM_NAME to $0 for anyone civilized aka some minimal C experience. Perl tends to be consistent. In a similar style, if you insist on implementing a global general variable like $PERL_VERSION which contains a string of pretty much what it sounds like it contains, to keep things consistent all general vars also have a single character synonym, so welcome to $"control-V" In the "real world" you can write something stupid enough to get yourself fired. This kind of activity probably qualifies unless you have an excellent excuse. Perhaps if you have a complicated if-then statement with numerous clauses and using one individual weird, yet short, variable name allows a debugging programmer to keep the whole control flow in their head instead of scrolling the mess off the screen, then, maybe, its a win. But I wouldn't make a habit of it. Given that you can pretty much transparently "upgrade" or "downgrade" the code with a simple search and replace its not a major crisis. A lot of people use Perl::Critic as a Perl "lint" and a lot of those users put large amounts of the perlvars file in the Variables::ProhibitEvilVariables test although the Perl::Critic authors don't by default include them, which many people consider a bug in Perl::Critic but whatever.
- gpvos 12y ago
  > Perl tends to be consistent. Well, for a certain kind of consistency, yes. From the perlfunc manpage, about the return values of Perl's operators and functions in scalar versus list context: In general, they do what you want, unless you want consistency.
- Mithaldu 12y ago
  > Its probably more "civilized" to call it $PROGRAM_NAME in your code, but whatever. I don't think this is controversial to alias $PROGRAM_NAME to $0 for anyone civilized aka some minimal C experience. There is `use English;` for that. :)
- pflanze 12y ago

emmelaich 12y ago

Could be worse! "Why does Java allow control characters in its identifiers?" http://stackoverflow.com/questions/4838507/why-does-java-allow-control-characters-in-its-identifiers http://stackoverflow.com/questions/4838507/why-does-java-all...