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### Re^2: How to create loop in perl dynamically

 on Sep 26, 2012 at 14:12 UTC ( #995780=note: print w/replies, xml ) Need Help??

in reply to Re: How to create loop in perl dynamically
in thread How to create loop in perl dynamically

Not sure how to do this. But will try this.
• Comment on Re^2: How to create loop in perl dynamically

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Re^3: How to create loop in perl dynamically
by djerius (Beadle) on Sep 26, 2012 at 16:49 UTC
Your problem requires the following
• The number of loops
• The iteration ranges for each loop
• Code which uses the loop indices
You can encode the first two however you'd like; in the following example I've simply put the ranges in an array.

You haven't provided an example of the code which runs inside the innermost loop. It might be useful if you provided some idea of what you're trying to do inside of those loops.

I'm assuming that your code only needs to know the loop indices.

Here's how you can use Math::Cartesian::Product:

```use Math::Cartesian::Product;

# this encodes the number of loops and their ranges
my @ranges = ( [ 0..1 ], [ 1..2 ], [2..3] );

# the code inside the braces is run for every combination
# of the ranges
cartesian {

print "indices: @_\n";

}  @ranges;

# here's a version using a subroutine which sums up
# the indices (just to do something with them)
sub compute {

my \$sum = 0;
\$sum += \$_ foreach @_;

print "sum of @_ = \$sum\n";

}

cartesian \&compute, @ranges;
And here are the results:
```indices: 0 1 2
indices: 0 1 3
indices: 0 2 2
indices: 0 2 3
indices: 1 1 2
indices: 1 1 3
indices: 1 2 2
indices: 1 2 3
sum of 0 1 2 = 3
sum of 0 1 3 = 4
sum of 0 2 2 = 4
sum of 0 2 3 = 5
sum of 1 1 2 = 4
sum of 1 1 3 = 5
sum of 1 2 2 = 5
sum of 1 2 3 = 6
Thank you. That was helpful.
This is requirement.
1. I have data in DB
ex: of data in DB.
```Student|Subject|Marks
aaa|eur|100
aaa|usd|90
aaa|eur|101
aaa|usd|80
aaa|eur|90
---------
bbb|usd|80
bbb|usd|100

.......
So Mapping goes like below:
```aaa->eur->100
aaa->eur->101
aaa->eur->90

aaa->usd->90
aaa->usd->80

Output will be : 1.If level=2
```aaa,eur,sum(100,101,90)
aaa,usd,sum(90,80)
so on..

2.If level is 3, we have more detailed level
```aaa,eur,100,sum(gg)
aaa,eur,100,sum(hh)
aaa,eur,101,sum(gf)
aaa,eur,101,sum(s)
aaa,eur,90,sum(dd)
aaa,eur,90,sum(sf)
aaa,usd,90,sum(eq)
...
Here its the users choice if u want to print at 2 level or 3 level or more..
If level is 4 then we go into detailed level.

Hope this requirement helps
I want to dynamically store the values in arrays and iterate through these arrays and get this values.
I think you're using the wrong data structure for your data; use hashes, not arrays.

Read your data in, split it into fields, then construct nested data structures to hold your data. The Perl Data Structures Cookbook (perldsc) has all of the information you need.

You can then either directly extract the information at the requested level or use Data::Path or Data::DPath.

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