Array to columns basics

casperdaghost · 07-20-2011, 08:54 PM

I have an array with 15 elements, and I want to break it down into three columns.
When the array is split into a the three elements - however on the iteration, it does not conform to that structure.

Code:

#!/usr/bin/perl -w 
use strict ; 
my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey", "praying mantis", "grouper", "mountain cat", "red ant","mahi mahi", "wolf", "gypsy moth", "clown fish", " grizzly bear", "japanese beetle" ); 
print  "FISH  ----  ANIMAL   ---- INSECT \n";
foreach my $line(@array) {
my ($fish , $animal, $insect ) = split ( ',', $line); 
print "$fish\n"; 
 }

i figured that it would just print out into one column - all the fish under the column FIDH. However, it just prints out the whole array.

Code:

FISH  ----  ANIMAL   ---- INSECT
striped bass
german shepard
housefly
bluefish
monkey
praying mantis
grouper
mountain cat
red ant
mahi mahi
wolf
gypsy moth
clown fish
 grizzly bear
japanese beetle

what I am looking for is a array strategy that will print out
in this format:

Code:

FISH  ----     ANIMAL   ----    INSECT
striped bass   german shepard   housefly
bluefish       monkey           praying mantis
grouper        mountain cat     red ant
mahi mahi      wolf             gypsy moth
clown fish     grizzly bear     Japanese beetle

The data in the array is consistent - I need it to newline every third element.

casperdaghost · 07-20-2011, 09:13 PM

When i get rid of the foreach loop it prints out in format, but only
prints out the first line.

Code:

#!/usr/bin/perl -w 
use strict ; 
my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey", "praying mantis", "grouper", "mountain cat", "red ant","mahi mahi", "wolf", "
gypsy moth", "clown fish", " grizzly bear", "japanese beetle" ); 
print  "FISH--------- ANIMAL---------  INSECT\n";
my ($fish , $animal, $insect ) = @array ;  
print "$fish  $animal    $insect \n";

I would like to get the same structure, however for each element in the array.
all 15 elements
This is results of above:

Code:

casper-compaq@compaq:~/work_perl$ /usr/bin/perl  shray
FISH--------- ANIMAL---------  INSECT
striped bass  german shepard    housefly

casperdaghost · 07-20-2011, 09:41 PM

this does not work either

Code:

#!/usr/bin/perl -w 
use strict ; 
my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey", "praying mantis", "grouper", "mountain cat", "red ant","mahi mahi", "wolf", "
gypsy moth", "clown fish", " grizzly bear", "japanese beetle" ); 
print  "FISH--------- ANIMAL---------  INSECT\n";
while (<@array>) { 
my ($fish , $animal, $insect ) =  split(',', $_) ;  
print "$fish\n"; 
sleep 1; 
}

grail · 07-20-2011, 10:20 PM

Your logic is flawed. You are to busy thinking of the outcome but not thinking about the input.

What if I asked you to print the 3 x N elements of the array (ie 3rd, 6th, 9th, etc). How would accomplish this?

casperdaghost · 07-21-2011, 12:08 AM

Every third element -
this is the only way that I know.

Code:

#!/usr/bin/perl -w 
use strict ; 
my $i ; 
my @array = ('striped bass', 'german shepard', 'housefly', 'bluefish', 'monkey', 'praying mantis', 'grouper', 'mountain cat', 'red ant','mahi mahi', 'wolf', 'gypsy moth', 'clown fish', ' grizzly bear', 'japanese beetle' ); 
@array = grep {not ++$i % 3} @array; 
 print "@array\n";

which is going to give us just the insects.

Code:

housefly praying mantis red ant gypsy moth japanese beetle

grail · 07-21-2011, 12:12 AM

hmmm ... what if i said you need to combine a for loop with your previous construct:

Code:

my ($fish , $animal, $insect ) = @array ;

I am not trying to be difficult, but more the old adage of teaching you to fish instead of giving them to you

casperdaghost · 07-21-2011, 12:34 AM

Code:

#!/usr/bin/perl -w 
use strict ; 
my $i; 
my $j = 3; 
my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey", "praying mantis", "grouper", "mountain cat", "red 
ant","mahi mahi", "wolf", "gypsy moth", "clown fish", " grizzly bear", "japanese beetle" ); 
print  "FISH--------- ANIMAL---------  INSECT\n";
for ($i = 2 ; $i <=$#array; $i = $i + $j  ){ 
print "                               $array[$i]\n"; 
sleep 1; 
}

produces

Code:

FISH--------- ANIMAL---------  INSECT
                               housefly
                               praying mantis
                               red ant
                               gypsy moth
                               japanese beetle

casperdaghost · 07-21-2011, 12:56 AM

The third column is nested under the first, and it prints out 5 times for every one.
i run into ths issue alot, i dont really understand how to scope this.

Code:

#!/usr/bin/perl -w 
use strict ; 
my $i; 
my $j = 3; 
my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey", "praying mantis", "grouper", "mountain cat", "red 
ant","mahi mahi", "wolf", "gypsy moth", "clown fish", " grizzly bear", "japanese beetle" ); 
print  "FISH--------- ANIMAL---------  INSECT\n";
for ($a =0; $a<=$#array; $a = $a + $j){
	print "$array[$a]\n"; 
        	for ($i = 2 ; $i <=$#array; $i = $i + $j  ){ 
print "                               $array[$i]\n"; 
                 } 
} 
casper-compaq@compaq:~/work_perl$ /usr/bin/perl  shray5
FISH--------- ANIMAL---------  INSECT
striped bass
                               housefly
                               praying mantis
                               red ant
                               gypsy moth
                               japanese beetle
bluefish
                               housefly
                               praying mantis
                               red ant
                               gypsy moth
                               japanese beetle

casperdaghost · 07-21-2011, 12:58 AM

if i scope each 'for' loop independently, as opposed to nesting each one under the other, and have one each 'for' loop execute one after the other i get this (i omit the middle loop for clarity) :

Code:

FISH--------- ANIMAL---------  INSECT
striped bass
bluefish
grouper
mahi mahi
clown fish
                               housefly
                               praying mantis
                               red ant
                               gypsy moth
                               japanese beetle

I dont care when three for loops execute, concurrently or one after the other, I just want all the data lined up in one table

Nominal Animal · 07-21-2011, 01:47 AM

Use a loop over the data rows, and either print all columns on that row at once, or use an inner loop to print just the columns on that row. If you have a fixed number of columns, the one print command is usually a better choice. If you have a loop, you need to remember to add an end-of-this-row (newline!) after the last column on each row.

grail · 07-21-2011, 02:12 AM

Ok ... so it turns out we have both learnt something. My thinking was that every time you did the following within a loop:

Code:

my ($fish , $animal, $insect ) = @array ;

That you would get the next 3 items of the array. Instead you just get the same 3 items each time

So this is the way I went:

Code:

#!/usr/bin/perl -v

use strict;
use warnings;

my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey", "praying mantis", "grouper", "mountain cat", "red ant","mahi mahi", "wolf", "gypsy moth", "clown fish", " grizzly bear", "japanese beetle" ); 

print  "FISH --------- ANIMAL --------- INSECT\n";

my $count = 1;

while ( scalar ( @array ) > 0 )
{
    print shift ( @array );

    if ( $count++ % 3 > 0 )
    {
        print " --- ";
    }
    else
    {
        print "\n";
    }
}

Now I am sure there are perlites out there to show you much more efficient ways (maybe even what I was trying to do),
but this seems to work, although the formatting needs some work.

grail · 07-21-2011, 04:00 AM

Ok ... found kind of what I was thinking of earlier:

Code:

#!/usr/bin/perl

use warnings;
use strict;

my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey", "praying mantis", "grouper", "mountain cat", "red ant","mahi mahi", "wolf", "gypsy moth", "clown fish", " grizzly bear", "japanese beetle" );

print  "FISH ANIMAL INSECT\n";

my @temp = @array;

for ( my $i = 1; $i <= (@array / 3); $i++ )
{
        my @temp2 = splice( @temp, 0, 3);

        print "@temp2\n";
}

Nominal Animal · 07-21-2011, 05:27 AM

I'm definitely not a Perl person, but I was thinking of

Code:

#!/usr/bin/perl -w 

use warnings;
use strict;

my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey",
             "praying mantis", "grouper", "mountain cat", "red ant","mahi mahi",
             "wolf", "gypsy moth", "clown fish", "grizzly bear", "japanese beetle" ); 

print  "FISH ---------- ANIMAL -------- INSECT --------\n";

for (my $i = 0; $i < $#array; $i += 3) {
	printf "%-15s %-15s %s\n", @array[ ($i) .. ($i+2) ];
}

or, with less formatting (just horizontal tabs between columns) but adjustable number of columns,

Code:

#!/usr/bin/perl -w 

use warnings;
use strict;

my @array = ("striped bass", "german shepard", "housefly", "bluefish", "monkey",
             "praying mantis", "grouper", "mountain cat", "red ant","mahi mahi",
             "wolf", "gypsy moth", "clown fish", "grizzly bear", "japanese beetle" ); 

my @header = ("FISH", "ANIMAL", "INSECT");

$, = "\t";
$\ = "\n";

print @header;
for (my $i = 0; $i < $#array; $i += 1 + $#header) {
	print @array[ ($i) .. ($i + $#header) ];
}

grail · 07-21-2011, 09:42 AM

Much cleaner

I knew there had to be better ways.