Hello again,
I wasn't able to continue with the project I was working on way back in
September, but I wanted to send a quick note to thank everyone (Andy Bach, Jim
Gibson, Rob Dixon and Mike Flannigan) for their help. I apologize for not
following up sooner. Hopefully I'll have some time to get back to it some day
soon; I was a little optimistic in my planning. Thanks again!
On Sep 4, 2013, at 10:55 PM, beginners-digest-h...@perl.org wrote:
>
> beginners Digest 5 Sep 2013 03:55:27 -0000 Issue 4576
>
> Topics (messages 123410 through 123433):
>
> Re: Recursive Validation Function
> 123410 by: Andy Bach
> 123411 by: Jim Gibson
> 123412 by: Rob Dixon
> 123413 by: Rob Dixon
> 123427 by: Mike Flannigan
>
>
> ----------------------------------------------------------------------
>
> From: Andy Bach <afb...@gmail.com>
> Date: September 2, 2013 8:43:59 PM CDT
> To: John Aten <welcome.to.eye.o.r...@gmail.com>
> Cc: "beginners@perl.org" <beginners@perl.org>
> Subject: Re: Recursive Validation Function
>
>
>
>
> On Monday, September 2, 2013, John Aten wrote:
> my $valid_token = validate_tokens($token);
>
>
> Too bad it doesn't work! Even if I put in valid tokens on the first shot,
> there are errors:
>
> You're passing the token as a parameter to the sub but the is using $_ for
> the match. You need to assign the parameter in the sub. They arrive on the
> global @_ array; one idiom is
> sub validate_token {
> my ($test_token) = @_;
>
> This assigns the first passed parameter to test_token. The advantage being of
> you add more params you can just insert a new var. in the LHS list:
> my ($test_token, $empty_allowed, $cleanup) = @_;
>
> Now use $test_token instead of $_
>
>
>
> I am writing a script to rename files. The script prompts the user to enter
> tokens which will comprise part of the file name. These are made of letters
> and numbers separated by a dot, ie: R.3. The letters can be R, I or C, upper
> or lowercase. The first number can be one through eight, and if it is a six
> there can be an additional dot followed by a one or two. To make sure that I
> don't make any mistakes when putting in these tokens, I have tried to write a
> function to make sure that they are valid:
>
> sub validate_tokens {
> if ($_ !~ /^[ric]\.[1234578]$/i) {
> if ($_ !~ /^[ric]\.6(\.[1|2])?$/i) {
> print "Enter valid tokens: ";
> my $new_token = <STDIN>;
> chomp $new_token;
> validate_tokens($new_token);
> }
> }
> return $_;
> }
>
>
> I'm calling it like this:
>
> print "Enter Tokens: ";
> my $token = <STDIN>;
> chomp $token;
> my $valid_token = validate_tokens($token);
>
>
> Too bad it doesn't work! Even if I put in valid tokens on the first shot,
> there are errors:
>
> Use of uninitialized value $_ in pattern match (m//) at bulk.pl line 65,
> <STDIN> line 3.
> Use of uninitialized value $_ in pattern match (m//) at bulk.pl line 66,
> <STDIN> line 3.
>
> Lines 65 and 66 are the ones with the two if statements, lines 2 and 3 of the
> first code snippet above. Each time I run it, the <STDIN> line number in the
> error message increases by one. The script goes into an infinite loop,
> prompting for valid tokens, but even if valid ones are entered it continues.
> What am I missing?
> --
> To unsubscribe, e-mail: beginners-unsubscr...@perl.org
> For additional commands, e-mail: beginners-h...@perl.org
> http://learn.perl.org/
>
>
>
>
> --
>
> a
>
> Andy Bach,
> afb...@gmail.com
> 608 658-1890 cell
> 608 261-5738 wk
>
>
>
> From: Jim Gibson <jimsgib...@gmail.com>
> Date: September 3, 2013 12:56:16 AM CDT
> To: "begin >> Perl Beginners" <beginners@perl.org>
> Subject: Re: Recursive Validation Function
>
>
>
> On Sep 2, 2013, at 6:23 PM, John Aten wrote:
>
>> Hello all,
>>
>> I am writing a script to rename files. The script prompts the user to enter
>> tokens which will comprise part of the file name. These are made of letters
>> and numbers separated by a dot, ie: R.3. The letters can be R, I or C, upper
>> or lowercase. The first number can be one through eight, and if it is a six
>> there can be an additional dot followed by a one or two. To make sure that I
>> don't make any mistakes when putting in these tokens, I have tried to write
>> a function to make sure that they are valid:
>
> Use $_[0] instead of $_ or the other suggestions from Andy.
>
>>
>> sub validate_tokens {
>> if ($_ !~ /^[ric]\.[1234578]$/i) {
>> if ($_ !~ /^[ric]\.6(\.[1|2])?$/i) {
>
> The '[1|2]' part of this regular expression is incorrect. Characters in a
> character class do not need the pipe character for alternation. They are
> already treated as alternates. This part should be '[12]'. Your pattern will
> match the string 'r.6|'
>
> You can combine the two regular expressions by using alternation and
> non-capturing grouping (clustering):
>
> if( $_[0] !~ /^[ric]\.(?:[1-578])|(?:6(\.[12])?)$/i ) {
> ...
>
> For readability, use the extended form and the more modern zero-width
> assertions \A and \z:
>
> if( $_[0] !~ m{ \A [ric] \. (?:[1-578]) | (?:6 (\.[12])? ) \z }ix ) {
> ...
>
>> print "Enter valid tokens: ";
>> my $new_token = <STDIN>;
>> chomp $new_token;
>> validate_tokens($new_token);
>> }
>> }
>> return $_;
>> }
>>
>>
>> I'm calling it like this:
>>
>> print "Enter Tokens: ";
>> my $token = <STDIN>;
>> chomp $token;
>> my $valid_token = validate_tokens($token);
>>
>>
>> Too bad it doesn't work! Even if I put in valid tokens on the first shot,
>> there are errors:
>>
>> Use of uninitialized value $_ in pattern match (m//) at bulk.pl line 65,
>> <STDIN> line 3.
>> Use of uninitialized value $_ in pattern match (m//) at bulk.pl line 66,
>> <STDIN> line 3.
>>
>> Lines 65 and 66 are the ones with the two if statements, lines 2 and 3 of
>> the first code snippet above. Each time I run it, the <STDIN> line number in
>> the error message increases by one. The script goes into an infinite loop,
>> prompting for valid tokens, but even if valid ones are entered it continues.
>> What am I missing?
>> --
>> To unsubscribe, e-mail: beginners-unsubscr...@perl.org
>> For additional commands, e-mail: beginners-h...@perl.org
>> http://learn.perl.org/
>>
>>
>
>
>
>
> From: Rob Dixon <rob.di...@gmx.com>
> Date: September 3, 2013 3:32:26 AM CDT
> To: beginners@perl.org
> Cc: John Aten <welcome.to.eye.o.r...@gmail.com>
> Subject: Re: Recursive Validation Function
>
>
> On 03/09/2013 02:23, John Aten wrote:
>> Hello all,
>>
>> I am writing a script to rename files. The script prompts the user
>> to enter tokens which will comprise part of the file name. These are
>> made of letters and numbers separated by a dot, ie: R.3. The
>> letters can be R, I or C, upper or lowercase. The first number can be
>> one through eight, and if it is a six there can be an additional dot
>> followed by a one or two. To make sure that I don't make any
>> mistakes when putting in these tokens, I have tried to write a
>> function to make sure that they are valid:
>>
>> sub validate_tokens {
>> if ($_ !~ /^[ric]\.[1234578]$/i) {
>> if ($_ !~ /^[ric]\.6(\.[1|2])?$/i) {
>> print "Enter valid tokens: ";
>> my $new_token = <STDIN>;
>> chomp $new_token;
>> validate_tokens($new_token);
>> }
>> }
>> return $_;
>> }
>>
>>
>> I'm calling it like this:
>>
>> print "Enter Tokens: ";
>> my $token = <STDIN>;
>> chomp $token;
>> my $valid_token = validate_tokens($token);
>>
>>
>> Too bad it doesn't work! Even if I put in valid tokens on the first shot,
>> there are errors:
>>
>> Use of uninitialized value $_ in pattern match (m//) at bulk.pl line 65,
>> <STDIN> line 3.
>> Use of uninitialized value $_ in pattern match (m//) at bulk.pl line 66,
>> <STDIN> line 3.
>>
>> Lines 65 and 66 are the ones with the two if statements, lines 2 and
>> 3 of the first code snippet above. Each time I run it, the <STDIN>
>> line number in the error message increases by one. The script goes
>> into an infinite loop, prompting for valid tokens, but even if valid
>> ones are entered it continues. What am I missing?
>
> As has been explained, the parameter to your subroutine is in @_. $_ could
> contain anything, and clearly is undefined at this point.
>
> It is also a misuse of recursion as it stands. You should use the subroutine
> just for verification, and put a reprompt loop outside it.
>
> Try this for your subroutine
>
> sub validate_tokens {
> $_[0] =~ /^[ric]\.(?:6\.[12]|[1-8])$/i;
> }
>
> and call it like this
>
> my $token;
> print "Enter Tokens: ";
> while () {
> $token = <STDIN>;
> chomp $token;
> last if validate_tokens($token);
> print "Enter valid tokens: ";
> }
>
> HTH,
>
> Rob
>
>
>
>
> From: Rob Dixon <rob.di...@gmx.com>
> Date: September 3, 2013 3:35:37 AM CDT
> To: Perl Beginners <beginners@perl.org>
> Cc: Jim Gibson <jimsgib...@gmail.com>
> Subject: Re: Recursive Validation Function
>
>
> On 03/09/2013 06:56, Jim Gibson wrote:
>>
>> For readability, use the extended form and the more modern
>> zero-width assertions \A and \z:
>>
>> if ( $_[0] !~ m{ \A [ric] \. (?:[1-578]) | (?:6 (\.[12])? ) \z }ix ) {
>
> Hi Jim
>
> You have incorrect parentheses. Your regex matches
>
> \A [ric] \. (?:[1-578])
>
> or
>
> (?:6 (\.[12])? ) \z
>
> which isn't what is wanted at all!
>
> Rob
>
>
>
> From: Mike Flannigan <mikef...@att.net>
> Date: September 4, 2013 7:26:58 AM CDT
> To: beginners@perl.org
> Cc: welcome.to.eye.o.r...@gmail.com
> Subject: Re: Recursive Validation Function
>
>
>
> On 9/2/2013 8:23 PM, John wrote:
>>
>> Hello all,
>>
>> I am writing a script to rename files. The script prompts the user to enter
>> tokens which will comprise part of the file name. These are made of letters
>> and numbers separated by a dot, ie: R.3. The letters can be R, I or C, upper
>> or lowercase. The first number can be one through eight, and if it is a six
>> there can be an additional dot followed by a one or two. To make sure that I
>> don't make any mistakes when putting in these tokens, I have tried to write
>> a function to make sure that they are valid:
>>
>> sub validate_tokens {
>> if ($_ !~ /^[ric]\.[1234578]$/i) {
>> if ($_ !~ /^[ric]\.6(\.[1|2])?$/i) {
>> print "Enter valid tokens: ";
>> my $new_token = <STDIN>;
>> chomp $new_token;
>> validate_tokens($new_token);
>> }
>> }
>> return $_;
>> }
>>
>>
>> I'm calling it like this:
>>
>> print "Enter Tokens: ";
>> my $token = <STDIN>;
>> chomp $token;
>> my $valid_token = validate_tokens($token);
>>
>>
>> Too bad it doesn't work! Even if I put in valid tokens on the first shot,
>> there are errors:
>>
>> Use of uninitialized value $_ in pattern match (m//) at bulk.pl line 65,
>> <STDIN> line 3.
>> Use of uninitialized value $_ in pattern match (m//) at bulk.pl line 66,
>> <STDIN> line 3.
>>
>> Lines 65 and 66 are the ones with the two if statements, lines 2 and 3 of
>> the first code snippet above. Each time I run it, the <STDIN> line number in
>> the error message increases by one. The script goes into an infinite loop,
>> prompting for valid tokens, but even if valid ones are entered it continues.
>> What am I missing?
>
> Howdy.
>
> In your subroutine replace "$_" with "$_[0]" in
> 3 places. Then it may still be broke, but it
> will function better.
>
>
> Mike
>
>
>
>
>
>
> Mirabeau | MMS Dr. C.J.K. van Aalstweg 8F 301, 1625 NV Hoorn
> +31(0)20-5950550 - - www.mirabeau.nl
>
>
