problem with PDL

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

Hi there
I'm currently trying to get to grips with the PDL module .. i'm wanting to calculate the determinant for a 4x4 matrix. This is the code I've managed to create so far

#!/usr/bin/perl -w

use strict;

use PDL::MatrixOps;

my $mat = pdl [
           [3.4603, 1.7529, 1.6990,2.1181],
           [ 2.5459,2.5615,2.2525,2.3606],
           [ 2.3606, 2.2515, 2.5628,2.5459],
           [ 2.1181,1.6982,1.7537,3.4603],
           ];

my $det = determinant($mat);

print "$det\n";
[download]

But it comes up with a syntax error

syntax error at ./test.pl line 7, near "pdl ["
Execution of ./test.pl aborted due to compilation errors.
[download]

Any help much appreciated

Comment on problem with PDL Select or Download Code

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Re: problem with PDL by zentara (Cardinal) on Jun 30, 2005 at 12:34 UTC
You need to "use PDL". `#!/usr/bin/perl use warnings; use strict; use PDL; use PDL::MatrixOps; ..... ....` [download] I'm not really a human, but I play one on earth. flash japh	[reply] [d/l]
Re^2: problem with PDL by VSarkiss (Monsignor) on Jun 30, 2005 at 13:56 UTC
You're correct, but once you `use PDL`, it's no longer necessary to `use PDL::MatrixOps` (although it's harmless to do so). Do not rebuke them with harsh words ... but rather lead them gently - with URLs - so that they may learn wisdom.	[reply] [d/l] [select]
Re: problem with PDL by marto (Cardinal) on Jun 30, 2005 at 12:16 UTC
Hi, This is untested, but should that read: `my $mat = PDL::Matrix->pdl [` [download] Hope this helps. Martin	[reply] [d/l]
Re: problem with PDL by Angharad (Pilgrim) on Jun 30, 2005 at 15:25 UTC
Thanks. Adding use::PDL worked a treat :)	[reply]
Re: problem with PDL by anonymized user 468275 (Curate) on Jun 30, 2005 at 12:19 UTC
...and then you'll get another syntax error (nothing after the last comma). One world, one people	[reply]
Re^2: problem with PDL by VSarkiss (Monsignor) on Jun 30, 2005 at 13:52 UTC
That's not a syntax error. Look at perldata, under "List Value Constructors", and you'll note: You may have an optional comma before the closing parenthesis of a list literal, so that you can say: `@foo = ( 1, 2, 3, );` [download] That makes it particularly easy to line up all the list elements vertically, and add and remove elements easily. Do not rebuke them with harsh words ... but rather lead them gently - with URLs - so that they may learn wisdom.	[reply] [d/l]
Re^3: problem with PDL by anonymized user 468275 (Curate) on Jun 30, 2005 at 14:01 UTC
thanks - I often have to parse perl (e.g. searching and extracting from project code) so now I will have to adjust my rules to allow for unclosed lists. One world, one people	[reply]
Re^2: problem with PDL by marto (Cardinal) on Jun 30, 2005 at 12:23 UTC
Ah, Well spotted sir :) Update: Looks like I spoke too soon :) Martin	[reply]
Re^2: problem with PDL by polettix (Vicar) on Jun 30, 2005 at 13:14 UTC
I cannot install PDL at the moment because I'm not on "my" machine, but I was wondering why this should lead to a syntax error. `~/sviluppo/perl> cat prova.pl #!/usr/bin/perl use strict; use warnings; use Data::Dumper; my $mat = [ [3.4603, 1.7529, 1.6990,2.1181], [ 2.5459,2.5615,2.2525,2.3606], [ 2.3606, 2.2515, 2.5628,2.5459], [ 2.1181,1.6982,1.7537,3.4603], # <-- trailing comma ]; print Dumper($mat); ~/sviluppo/perl> perl prova.pl $VAR1 = [ [ '3.4603', '1.7529', '1.699', '2.1181' ], [ '2.5459', '2.5615', '2.2525', '2.3606' ], [ '2.3606', '2.2515', '2.5628', '2.5459' ], [ '2.1181', '1.6982', '1.7537', '3.4603' ] ];` [download] Neither errors nor warnings. I think that the list constructor doesn't complain about trailing "hanging" commas because you're able to cut-and-paste lines (like in this example) without the need to treat the last line differently. Is it different when PDL comes in? Flavio perl -ple'$_=reverse' <<<ti.xittelop@oivalf Don't fool yourself.	[reply] [d/l]