Use of uninitialized value within

gary16 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Use of uninitialized value within by Corion (Patriarch) on Feb 03, 2015 at 08:21 UTC
Have you looked at the values of `$tmp1`? Most likely, `$tmp1` gets a value larger than the number of elements of `@parr`, and that's why you get the warning. Update: I found the following line instructive: `printf "%d: %d -> %s\n", $i, $tmp1, $parr[$tmp1];` [download]	[reply] [d/l] [select]
Re^2: Use of uninitialized value within by gary16 (Novice) on Feb 04, 2015 at 01:23 UTC
Thanks guy,I have found the mistake.My array index is out of range.	[reply]
Re: Use of uninitialized value within by pme (Monsignor) on Feb 03, 2015 at 09:22 UTC
In case of errors/warnings you can use splain to get explanation: `$ perl yourprogram.pl 2>&1 >/dev/null \| splain` [download]	[reply] [d/l]
Re^2: Use of uninitialized value within by Anonymous Monk on Feb 03, 2015 at 11:47 UTC
perl -Mdiagnostics needsplaining.pl	[reply]
Re: Use of uninitialized value within by BillKSmith (Monsignor) on Feb 03, 2015 at 14:47 UTC
I am unable to duplicate your problem with my perl v5.16.3. I can suggest several improvements to your code. Always use strict and warnings. Use of printf with only a format is confusing. Use print Your math is unnecessarily complicated. `use strict; use warnings; use POSIX qw(floor); my @PC1=(58,50,42,34,26,18,10,2, 60,52,44,36,28,20,12,4, 62,54,46,38,30,22,14,6, 64,56,48,40,32,24,16,8, 57,49,41,33,25,17,9,1, 59,51,43,35,27,19,11,3, 61,53,45,37,29,21,13,5, 63,55,47,39,31,23,15,7); my @parr=('0','M','0','A','0','I','0','L'); print $parr[floor( $PC1[$_]/8 )], "\n" for (0..63);` [download] My use of 'floor' is not strictly necessary in this case, but is recommended for the reason explained in int.	[reply] [d/l]
Re^2: Use of uninitialized value within by AnomalousMonk (Archbishop) on Feb 03, 2015 at 17:51 UTC
I am unable to duplicate your problem with my perl v5.16.3. I can duplicate the problem with both Strawberry 5.14.4.1 and ActiveState 5.8.9, both under Win32. c:\@Work\Perl>perl -wMstrict -le "use POSIX qw(floor); ;; print 'perl version ', $]; ;; my @PC1=(58,50,42,34,26,18,10,2, 60,52,44,36,28,20,12,4, 62,54,46,38,30,22,14,6, 64,56,48,40,32,24,16,8, 57,49,41,33,25,17, 9,1, 59,51,43,35,27,19,11,3, 61,53,45,37,29,21,13,5, 63,55,47,39,31,23,15,7); ;; my @parr=('0','M','0','A','0','I','0','L'); printf $parr[floor( $PC1[$_]/8 )] for (0..63); " perl version 5.014004 Use of uninitialized value in printf at -e line 1. L0I0A0M0L0I0A0M0L0I0A0M0L0I0A0ML0I0A0M0L0I0A0M0L0I0A0M0L0I0A0M0 [download] As in the OPed code, the problem arises from the element of 64 in the `@PC1` array producing an index of 8 into the `@parr` array, the highest valid index of which is 7. Give a man a fish: `<%-(-(-(-<`	[reply] [d/l] [select]
Re^2: Use of uninitialized value within by AnomalousMonk (Archbishop) on Feb 04, 2015 at 00:52 UTC
Your math is unnecessarily complicated. One could further simplify the math by taking advantage of the fact that the `[ ]` subscript operator does its own 'floor' operation by just throwing away the fractional part of the (inherently) double number: c:\@Work\Perl>perl -wMstrict -le "use POSIX qw(floor); ;; print 'perl version ', $]; ;; my @PC1=(58,50,42,34,26,18,10,2, 60,52,44,36,28,20,12,4, 62,54,46,38,30,22,14,6, 64,56,48,40,32,24,16,8, 57,49,41,33,25,17, 9,1, 59,51,43,35,27,19,11,3, 61,53,45,37,29,21,13,5, 63,55,47,39,31,23,15,7); ;; my @parr = qw(0 M 0 A 0 I 0 L); printf $parr[floor( $PC1[$_]/8 )] for (0..63); print ''; printf $parr[ $_ / 8 ] for @PC1; " perl version 5.014004 Use of uninitialized value in printf at -e line 1. L0I0A0M0L0I0A0M0L0I0A0M0L0I0A0ML0I0A0M0L0I0A0M0L0I0A0M0L0I0A0M0 Use of uninitialized value in printf at -e line 1. L0I0A0M0L0I0A0M0L0I0A0M0L0I0A0ML0I0A0M0L0I0A0M0L0I0A0M0L0I0A0M0 [download] (Of course, this doesn't address the root problem of generating an index that's out of range!) Give a man a fish: `<%-(-(-(-<`	[reply] [d/l] [select]
Re^2: Use of uninitialized value within by GrandFather (Saint) on Feb 03, 2015 at 19:47 UTC
You don't see the warning because you didn't run the script with warnings turned on. Most likely the OP used -w on the command line to achieve that. Running the updated version of the script that you provided does show the warning. I guess you posted the code without running it? Perl is the programming world's equivalent of English	[reply]
Re^2: Use of uninitialized value within by BillKSmith (Monsignor) on Feb 03, 2015 at 23:06 UTC
Sorry guys, I missed the message when it scrolled off the screen. Bill	[reply]
Re: Use of uninitialized value within by Kita (Initiate) on Feb 03, 2015 at 13:54 UTC
`printf $parr[$tmp1]." - $i= @{ [ @PC1[$i] ] } tmp1=$tmp1\n";` [download] Try to print tmp1, with value 64, you havnt nothing for index 8 in array @parr ...	[reply] [d/l]
Re^2: Use of uninitialized value within by kennethk (Abbot) on Feb 03, 2015 at 16:43 UTC
Kita, when providing solutions, please wrap code in `<code>` tags to keep things properly formatted. Note how your square brackets got mangled into links. I presume you originally intended to write: `printf $parr[$tmp1]." - $i= @{ [ @PC1[$i] ] } tmp1=$tmp1\n";` [download] As a side note, you probably shouldn't use printf if print will do (there's no templating in your string), it seems odd that you are both concatenating and interpolating, and why use the baby carriage operator and a slice when a value would be equivalent; why not just `print "$parr[$tmp1] - $i= $PC1[$i] tmp1=$tmp1\n";` [download] #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.	[reply] [d/l] [select]
Re^3: Use of uninitialized value within by gary16 (Novice) on Feb 04, 2015 at 01:18 UTC
I m familiar with java a. And I have learn perl for a short time.So thank for your suggettion very much.	[reply]
Re: Use of uninitialized value within by Corion (Patriarch) on Feb 03, 2015 at 08:20 UTC
~~Have you looked at the values of `$tmp1`? Most likely, `$tmp1` gets a value larger than the number of elements of `@parr`, and that's why you get the warning.~~	[reply] [d/l] [select]