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Re: [PBML] Variable Interpolation

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  • mail meda
    Hi Raj, The code you gave just returns the name of the variable and not the value in it. Your code with call reference(group) gave f_group and not its value
    Message 1 of 20 , Jan 2, 2006
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      Hi Raj,

      The code you gave just returns the name of the variable and not the value in
      it.
      Your code with call 'reference(group) gave 'f_group' and not its value
      'PBML'.
      Any idea ?

      Thanks for your efforts.

      Expecting more response..

      Bye



      On 1/2/06, KalyanRaj <kalyanrajs@...> wrote:
      >
      > hi all,
      >
      > guide me if i'm wrong.
      >
      > I slightly modified the code
      >
      > #!/usr/bin/perl
      > sub reference {
      > $type = shift;
      > $f_group='PBML';
      > $f_lang='perl';
      > $f_os='linux';
      > $ref = "f_$type";
      > }
      > reference(perlgroup);
      > print $ref;
      >
      > $ref will contain the value of $type which is given at run-time. as you
      > mentioned $type = shift , I assumed a subroutine and passed value of $type
      > from the subroutine "reference". when we run the program $ref will have
      > f_perlgroup, where the value of $type will be substituted in $ref.
      >
      > we need to be very careful with variable interpolation with single and
      > double quotes.
      >
      > when we print $ref with single quotes , value of $type will not be
      > substituted. Variable interpolation will takes place only if we have
      > double
      > quotes.
      >
      > hope this has helped you ... if i assumed anything wrong guide me further.
      >
      > thanks,
      > KalyanRaj
      >
      > -----Original Message-----
      > From: perl-beginner@yahoogroups.com
      > [mailto:perl-beginner@yahoogroups.com]On Behalf Of mail meda
      > Sent: Monday, January 02, 2006 4:40 PM
      > To: perl-beginner@yahoogroups.com
      > Subject: [PBML] Variable Interpolation
      >
      >
      > Hi Friends,
      >
      > Can you please let me know how to get the content of a " value of the
      > variable ".
      > For Eg:
      >
      > my $type = shift;
      > my $f_group='PBML';
      > my $f_lang='perl';
      > my $f_os='linux';
      > my $ref = "f_$type";
      >
      > Where $type can be group,lang or os which is found during the runtime.
      >
      > How to get the result of the above in $ref variable.
      >
      > Thanks in advance.
      >
      >
      > [Non-text portions of this message have been removed]
      >
      >
      >
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      [Non-text portions of this message have been removed]
    • KalyanRaj
      hi , when we call subroutine reference(group) , output will be f_group which is not a scalar. $f_group and f_group have different meaning in Perl. Let me
      Message 2 of 20 , Jan 2, 2006
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        hi ,

        when we call subroutine ' reference(group) ', output will be f_group which
        is not a scalar.
        $f_group and f_group have different meaning in Perl.

        Let me know what exactly you want to do ...

        Regards,
        KalyanRaj



        -----Original Message-----
        From: perl-beginner@yahoogroups.com
        [mailto:perl-beginner@yahoogroups.com]On Behalf Of mail meda
        Sent: Monday, January 02, 2006 6:04 PM
        To: perl-beginner@yahoogroups.com
        Subject: Re: [PBML] Variable Interpolation


        Hi Raj,

        The code you gave just returns the name of the variable and not the value in
        it.
        Your code with call 'reference(group) gave 'f_group' and not its value
        'PBML'.
        Any idea ?

        Thanks for your efforts.

        Expecting more response..

        Bye



        On 1/2/06, KalyanRaj <kalyanrajs@...> wrote:
        >
        > hi all,
        >
        > guide me if i'm wrong.
        >
        > I slightly modified the code
        >
        > #!/usr/bin/perl
        > sub reference {
        > $type = shift;
        > $f_group='PBML';
        > $f_lang='perl';
        > $f_os='linux';
        > $ref = "f_$type";
        > }
        > reference(perlgroup);
        > print $ref;
        >
        > $ref will contain the value of $type which is given at run-time. as you
        > mentioned $type = shift , I assumed a subroutine and passed value of $type
        > from the subroutine "reference". when we run the program $ref will have
        > f_perlgroup, where the value of $type will be substituted in $ref.
        >
        > we need to be very careful with variable interpolation with single and
        > double quotes.
        >
        > when we print $ref with single quotes , value of $type will not be
        > substituted. Variable interpolation will takes place only if we have
        > double
        > quotes.
        >
        > hope this has helped you ... if i assumed anything wrong guide me further.
        >
        > thanks,
        > KalyanRaj
        >
        > -----Original Message-----
        > From: perl-beginner@yahoogroups.com
        > [mailto:perl-beginner@yahoogroups.com]On Behalf Of mail meda
        > Sent: Monday, January 02, 2006 4:40 PM
        > To: perl-beginner@yahoogroups.com
        > Subject: [PBML] Variable Interpolation
        >
        >
        > Hi Friends,
        >
        > Can you please let me know how to get the content of a " value of the
        > variable ".
        > For Eg:
        >
        > my $type = shift;
        > my $f_group='PBML';
        > my $f_lang='perl';
        > my $f_os='linux';
        > my $ref = "f_$type";
        >
        > Where $type can be group,lang or os which is found during the runtime.
        >
        > How to get the result of the above in $ref variable.
        >
        > Thanks in advance.
        >
        >
        > [Non-text portions of this message have been removed]
        >
        >
        >
        > Unsubscribing info is here:
        > http://help.yahoo.com/help/us/groups/groups-32.html
        > Yahoo! Groups Links
        >
        >
        >
        >
        >
        >
        >
        > Unsubscribing info is here:
        > http://help.yahoo.com/help/us/groups/groups-32.html
        > Yahoo! Groups Links
        >
        >
        >
        >
        >
        >
        >


        [Non-text portions of this message have been removed]



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      • merlyn@stonehenge.com
        ... mail Hi Friends, mail Can you please let me know how to get the content of a value of the mail variable . mail For Eg: mail my $type = shift; mail
        Message 3 of 20 , Jan 2, 2006
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          >>>>> "mail" == mail meda <mailmeda@...> writes:

          mail> Hi Friends,
          mail> Can you please let me know how to get the content of a " value of the
          mail> variable ".
          mail> For Eg:

          mail> my $type = shift;
          mail> my $f_group='PBML';
          mail> my $f_lang='perl';
          mail> my $f_os='linux';
          mail> my $ref = "f_$type";

          In Perl, the way to do this is to put the elements in a hash:

          my %mapping = (group => 'PBML', lang => 'perl', os => 'linux');
          my $type = shift;
          my $result = $mapping{$type};

          --
          Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
          <merlyn@...> <URL:http://www.stonehenge.com/merlyn/>
          Perl/Unix/security consulting, Technical writing, Comedy, etc. etc.
          See PerlTraining.Stonehenge.com for onsite and open-enrollment Perl training!
        • KalyanRaj
          hi , as mentioned by Randal, we can put elements in a hash... shift is a keyword in Perl which gives out first element in an array...I wonder is there
          Message 4 of 20 , Jan 2, 2006
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            hi ,

            as mentioned by Randal, we can put elements in a hash...
            "shift" is a keyword in Perl which gives out first element in an array...I
            wonder is there anyother use of "shift"
            when i'm executing the code given by Randal, nothing is printed out....

            MailMeda --- the below code print out PBML which is what you wanted. Also
            checkout the scope of the variables. if we place the statement
            print $result outside reference subroutine, it wont print anything.

            my %mapping = (group => 'PBML', lang => 'perl', os => 'linux');
            reference(group);
            sub reference {
            my $type = shift;
            my $result = $mapping{$type};
            print $result;
            }

            Regards,
            KalyanRaj

            -----Original Message-----
            From: perl-beginner@yahoogroups.com
            [mailto:perl-beginner@yahoogroups.com]On Behalf Of merlyn@...
            Sent: Monday, January 02, 2006 6:26 PM
            To: mail meda
            Cc: perl-beginner@yahoogroups.com
            Subject: Re: [PBML] Variable Interpolation


            >>>>> "mail" == mail meda <mailmeda@...> writes:

            mail> Hi Friends,
            mail> Can you please let me know how to get the content of a " value of the
            mail> variable ".
            mail> For Eg:

            mail> my $type = shift;
            mail> my $f_group='PBML';
            mail> my $f_lang='perl';
            mail> my $f_os='linux';
            mail> my $ref = "f_$type";

            In Perl, the way to do this is to put the elements in a hash:

            my %mapping = (group => 'PBML', lang => 'perl', os => 'linux');
            my $type = shift;
            my $result = $mapping{$type};

            --
            Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
            <merlyn@...> <URL:http://www.stonehenge.com/merlyn/>
            Perl/Unix/security consulting, Technical writing, Comedy, etc. etc.
            See PerlTraining.Stonehenge.com for onsite and open-enrollment Perl
            training!


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          • Shawn Corey
            ... You should always use an argument for shift. In this case, shift works on @_ since it is inside a subroutine. Outside any subroutine, shift works on @ARGV.
            Message 5 of 20 , Jan 2, 2006
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              KalyanRaj wrote:
              > as mentioned by Randal, we can put elements in a hash...
              > "shift" is a keyword in Perl which gives out first element in an array...I
              > wonder is there anyother use of "shift"
              > when i'm executing the code given by Randal, nothing is printed out....
              >
              > MailMeda --- the below code print out PBML which is what you wanted. Also
              > checkout the scope of the variables. if we place the statement
              > print $result outside reference subroutine, it wont print anything.
              >
              > my %mapping = (group => 'PBML', lang => 'perl', os => 'linux');
              > reference(group);
              > sub reference {
              > my $type = shift;
              > my $result = $mapping{$type};
              > print $result;
              > }

              You should always use an argument for shift. In this case, shift works
              on @_ since it is inside a subroutine. Outside any subroutine, shift
              works on @ARGV. To avoid confusion, always supply it with an argument.

              my $type = shift @_;


              --

              Just my 0.00000002 million dollars worth,
              --- Shawn

              "Probability is now one. Any problems that are left are your own."
              SS Heart of Gold, _The Hitchhiker's Guide to the Galaxy_

              * Perl tutorials at http://perlmonks.org/?node=Tutorials
              * A searchable perldoc is available at http://perldoc.perl.org/
            • merlyn@stonehenge.com
              ... Shawn You should always use an argument for shift. That s a bit strong. It s accepted to leave the argument off shift when it s being used in a sane way.
              Message 6 of 20 , Jan 2, 2006
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                >>>>> "Shawn" == Shawn Corey <shawn.corey@...> writes:

                Shawn> You should always use an argument for shift.

                That's a bit strong. It's accepted to leave the argument off shift
                when it's being used in a sane way. I presumed the original poster
                knew what he was doing, and didn't comment on that.

                --
                Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
                <merlyn@...> <URL:http://www.stonehenge.com/merlyn/>
                Perl/Unix/security consulting, Technical writing, Comedy, etc. etc.
                See PerlTraining.Stonehenge.com for onsite and open-enrollment Perl training!
              • Shawn Corey
                ... Yes, it s strong but all good discipline seems strong until you reap the benefits from it. I don t think it s sane for the implied behaviour of any
                Message 7 of 20 , Jan 2, 2006
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                  Randal L. Schwartz wrote:
                  >>>>>>"Shawn" == Shawn Corey <shawn.corey@...> writes:
                  >
                  >
                  > Shawn> You should always use an argument for shift.
                  >
                  > That's a bit strong. It's accepted to leave the argument off shift
                  > when it's being used in a sane way. I presumed the original poster
                  > knew what he was doing, and didn't comment on that.
                  >

                  Yes, it's strong but all good discipline seems strong until you reap the
                  benefits from it. I don't think it's sane for the implied behaviour of
                  any construct to change. What it means is that when I'm reading a
                  program, I have one more thing to keep track of. Anything that reduces
                  this overhead is worth the effort.

                  Always write your programs as though you aren't going to see them again
                  for 25 years and then have to make a critical change immediately.


                  --

                  Just my 0.00000002 million dollars worth,
                  --- Shawn

                  "Probability is now one. Any problems that are left are your own."
                  SS Heart of Gold, _The Hitchhiker's Guide to the Galaxy_

                  * Perl tutorials at http://perlmonks.org/?node=Tutorials
                  * A searchable perldoc is available at http://perldoc.perl.org/
                • KalyanRaj
                  Hi, Mail Meda - the following code will give you what you want....PBML. another version of code which uses hash and return sub reference { $type = shift;
                  Message 8 of 20 , Jan 2, 2006
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                    Hi,

                    Mail Meda - the following code will give you what you want....PBML.
                    another version of code which uses hash and return
                    sub reference {
                    $type = shift;
                    %types = (
                    group => "PBML",
                    lang => "Perl",
                    os => "Linux"
                    );
                    return $types{$type};
                    }
                    $result = reference("group");
                    print "$result\n";

                    Cheers,
                    KalyanRaj

                    -----Original Message-----
                    From: perl-beginner@yahoogroups.com
                    [mailto:perl-beginner@yahoogroups.com]On Behalf Of Shawn Corey
                    Sent: Monday, January 02, 2006 11:28 PM
                    To: perl-beginner@yahoogroups.com
                    Subject: Re: [PBML] Variable Interpolation


                    Randal L. Schwartz wrote:
                    >>>>>>"Shawn" == Shawn Corey <shawn.corey@...> writes:
                    >
                    >
                    > Shawn> You should always use an argument for shift.
                    >
                    > That's a bit strong. It's accepted to leave the argument off shift
                    > when it's being used in a sane way. I presumed the original poster
                    > knew what he was doing, and didn't comment on that.
                    >

                    Yes, it's strong but all good discipline seems strong until you reap the
                    benefits from it. I don't think it's sane for the implied behaviour of
                    any construct to change. What it means is that when I'm reading a
                    program, I have one more thing to keep track of. Anything that reduces
                    this overhead is worth the effort.

                    Always write your programs as though you aren't going to see them again
                    for 25 years and then have to make a critical change immediately.


                    --

                    Just my 0.00000002 million dollars worth,
                    --- Shawn

                    "Probability is now one. Any problems that are left are your own."
                    SS Heart of Gold, _The Hitchhiker's Guide to the Galaxy_

                    * Perl tutorials at http://perlmonks.org/?node=Tutorials
                    * A searchable perldoc is available at http://perldoc.perl.org/


                    Unsubscribing info is here:
                    http://help.yahoo.com/help/us/groups/groups-32.html
                    Yahoo! Groups Links
                  • Jenda Krynicky
                    From: Shawn Corey ... I would be a bit surprised if anyone wrote: sub foo { my $bar = shift(@_); ... and would wonder why. In this
                    Message 9 of 20 , Jan 3, 2006
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                      From: Shawn Corey <shawn.corey@...>
                      > Randal L. Schwartz wrote:
                      > >>>>>>"Shawn" == Shawn Corey <shawn.corey@...> writes:
                      > >
                      > >
                      > > Shawn> You should always use an argument for shift.
                      > >
                      > > That's a bit strong. It's accepted to leave the argument off shift
                      > > when it's being used in a sane way. I presumed the original poster
                      > > knew what he was doing, and didn't comment on that.
                      > >
                      >
                      > Yes, it's strong but all good discipline seems strong until you reap
                      > the benefits from it. I don't think it's sane for the implied
                      > behaviour of any construct to change. What it means is that when I'm
                      > reading a program, I have one more thing to keep track of. Anything
                      > that reduces this overhead is worth the effort.
                      >
                      > Always write your programs as though you aren't going to see them
                      > again for 25 years and then have to make a critical change
                      > immediately.

                      I would be a bit surprised if anyone wrote:

                      sub foo {
                      my $bar = shift(@_);
                      ...

                      and would wonder why. In this case it's a generally accepted that the
                      @_ gets omited. OTOH, I'd never make use of the fact that outside
                      subroutines shift() means shift(@ARGV). That's something lots of
                      people doesn't remember and something that might break easily if I
                      tried to move the piece of code into a subroutine.

                      Jenda
                      ===== Jenda@... === http://Jenda.Krynicky.cz =====
                      When it comes to wine, women and song, wizards are allowed
                      to get drunk and croon as much as they like.
                      -- Terry Pratchett in Sourcery
                    • merlyn@stonehenge.com
                      ... Jenda I would be a bit surprised if anyone wrote: Jenda sub foo { Jenda my $bar = shift(@_); Jenda ... Jenda and would wonder why. In this case
                      Message 10 of 20 , Jan 3, 2006
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                        >>>>> "Jenda" == Jenda Krynicky <Jenda@...> writes:

                        Jenda> I would be a bit surprised if anyone wrote:

                        Jenda> sub foo {
                        Jenda> my $bar = shift(@_);
                        Jenda> ...

                        Jenda> and would wonder why. In this case it's a generally accepted that the
                        Jenda> @_ gets omited. OTOH, I'd never make use of the fact that outside
                        Jenda> subroutines shift() means shift(@ARGV). That's something lots of
                        Jenda> people doesn't remember and something that might break easily if I
                        Jenda> tried to move the piece of code into a subroutine.

                        I agree with you there. However, for a five line program:

                        #!/usr/bin/perl
                        my $from = shift;
                        my $to = shift;
                        if (-e $to) { rename $to, "$to~" or warn "cannot backup $to: $!"; }
                        rename $from, $to or warn "Cannot rename $from to $to: $!";

                        Will anyone really not know what "shift" is doing there? Or confuse
                        it with shift(@_)?

                        That's the point of defaults... they're the defaults because they're
                        the most common thing you would do with that operator *in that context*.

                        --
                        Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
                        <merlyn@...> <URL:http://www.stonehenge.com/merlyn/>
                        Perl/Unix/security consulting, Technical writing, Comedy, etc. etc.
                        See PerlTraining.Stonehenge.com for onsite and open-enrollment Perl training!
                      • Shawn Corey
                        ... The key phrase being in that context . My issue is that the default depends on the context. If it was the same throughout the regardless of context, I
                        Message 11 of 20 , Jan 3, 2006
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                          merlyn@... wrote:
                          > That's the point of defaults... they're the defaults because they're
                          > the most common thing you would do with that operator *in that context*.
                          >

                          The key phrase being "in that context". My issue is that the default
                          depends on the context. If it was the same throughout the regardless of
                          context, I wouldn't have a problem. The problem is that when I see a
                          naked shift, I have to stop and remember the context. One more thing to
                          worry about while reading a program.


                          --

                          Just my 0.00000002 million dollars worth,
                          --- Shawn

                          "Probability is now one. Any problems that are left are your own."
                          SS Heart of Gold, _The Hitchhiker's Guide to the Galaxy_

                          * Perl tutorials at http://perlmonks.org/?node=Tutorials
                          * A searchable perldoc is available at http://perldoc.perl.org/
                        • merlyn@stonehenge.com
                          ... Shawn The key phrase being in that context . My issue is that the default Shawn depends on the context. If it was the same throughout the regardless of
                          Message 12 of 20 , Jan 3, 2006
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                            >>>>> "Shawn" == Shawn Corey <shawn.corey@...> writes:

                            Shawn> The key phrase being "in that context". My issue is that the default
                            Shawn> depends on the context. If it was the same throughout the regardless of
                            Shawn> context, I wouldn't have a problem. The problem is that when I see a
                            Shawn> naked shift, I have to stop and remember the context. One more thing to
                            Shawn> worry about while reading a program.

                            That's why I said "10 line program". If this were a 200 line program,
                            I wouldn't bury "shift" in the middle, unless it was within 10 lines
                            of the start of a subroutine.

                            I believe it is reasonable to ask a programmer to look back about
                            ten lines to figure out the general flow of the program. I don't
                            think it's reasonable to have to maintain "state" further than that,
                            which is why I argue for 10-20 line subroutines instead of most of
                            the monoliths that I see most people write.

                            --
                            Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
                            <merlyn@...> <URL:http://www.stonehenge.com/merlyn/>
                            Perl/Unix/security consulting, Technical writing, Comedy, etc. etc.
                            See PerlTraining.Stonehenge.com for onsite and open-enrollment Perl training!
                          • Shawn Corey
                            ... Large monoliths have given me the willies ever since 2001: A Space Odyssey came out ;) -- Just my 0.00000002 million dollars worth, ... Probability is
                            Message 13 of 20 , Jan 3, 2006
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                              Randal L. Schwartz wrote:
                              > I believe it is reasonable to ask a programmer to look back about
                              > ten lines to figure out the general flow of the program. I don't
                              > think it's reasonable to have to maintain "state" further than that,
                              > which is why I argue for 10-20 line subroutines instead of most of
                              > the monoliths that I see most people write.
                              >

                              Large monoliths have given me the willies ever since "2001: A Space
                              Odyssey" came out ;)


                              --

                              Just my 0.00000002 million dollars worth,
                              --- Shawn

                              "Probability is now one. Any problems that are left are your own."
                              SS Heart of Gold, _The Hitchhiker's Guide to the Galaxy_

                              * Perl tutorials at http://perlmonks.org/?node=Tutorials
                              * A searchable perldoc is available at http://perldoc.perl.org/
                            • mail meda
                              Hi Frnds, Thanks for your response. Bye. ... [Non-text portions of this message have been removed]
                              Message 14 of 20 , Jan 5, 2006
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                                Hi Frnds,

                                Thanks for your response.

                                Bye.


                                On 1/4/06, Shawn Corey <shawn.corey@...> wrote:
                                >
                                > Randal L. Schwartz wrote:
                                > > I believe it is reasonable to ask a programmer to look back about
                                > > ten lines to figure out the general flow of the program. I don't
                                > > think it's reasonable to have to maintain "state" further than that,
                                > > which is why I argue for 10-20 line subroutines instead of most of
                                > > the monoliths that I see most people write.
                                > >
                                >
                                > Large monoliths have given me the willies ever since "2001: A Space
                                > Odyssey" came out ;)
                                >
                                >
                                > --
                                >
                                > Just my 0.00000002 million dollars worth,
                                > --- Shawn
                                >
                                > "Probability is now one. Any problems that are left are your own."
                                > SS Heart of Gold, _The Hitchhiker's Guide to the Galaxy_
                                >
                                > * Perl tutorials at http://perlmonks.org/?node=Tutorials
                                > * A searchable perldoc is available at http://perldoc.perl.org/
                                >
                                >
                                > Unsubscribing info is here:
                                > http://help.yahoo.com/help/us/groups/groups-32.html
                                > Yahoo! Groups Links
                                >
                                >
                                >
                                >
                                >
                                >
                                >
                                >


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