I'm building a count matrix in Perl using AoA: my #aoa = () then call $aoa[$i][$j]++ whenever I need to increment a specific cell. Since some cells are not incremented at all, they are left undef (these are equivalent to 0 counts).
I would like to print some lines from the matrix, but I get errors for undef cells (which I would simply like to print as zeros). what should I do?
Use defined with a conditional operator (?:).
#!/usr/bin/perl
use strict;
use warnings;
my #matrix;
for my $i (0 .. 3) {
for my $j (0 .. 3) {
if (rand > .5) {
$matrix[$i][$j]++;
}
}
}
for my $aref (#matrix) {
print join(", ", map { defined() ? $_ : 0 } #{$aref}[0 .. 3]), "\n"
}
If you are using Perl 5.10 or later, you can use the defined-or operator (//).
#!/usr/bin/perl
use 5.012;
use warnings;
my #matrix;
for my $i (0 .. 3) {
for my $j (0 .. 3) {
if (rand > .5) {
$matrix[$i][$j]++;
}
}
}
for my $aref (#matrix) {
print join(", ", map { $_ // 0 } #{$aref}[0 .. 3]), "\n"
}
Classically:
print defined $aoa[$i][$j] ? $aoa[$i][$j] : 0;
Modern Perl (5.10 or later):
print $aoa[$i][$j] // 0;
That is a lot more succinct and Perlish, it has to be said.
Alternatively, run through the matrix before printing, replacing undef with 0.
use strict;
use warnings;
my #aoa = ();
$aoa[1][1] = 1;
$aoa[0][2] = 1;
$aoa[2][1] = 1;
for my $i (0..2)
{
print join ",", map { $_ // 0 } #{$aoa[$i]}[0..2], "\n";
}
Just an example, please modify the code to your requirements.
use strict;
use warnings;
my #aoa;
$aoa[1][3]++;
foreach my $i (1 .. 3){
foreach my $j (1 .. 3){
defined $aoa[$i][$j] ? print $aoa[$i][$j] : print "0";
print "\t";
}
print "\n";
}
Related
I have wrote the following program:
use strict;
use warnings;
use 5.010;
my $nodesNumber = 100 ;
my $communitiesNumber = 10;
my $prob_communities = 0.3;
for my $i (1 .. $nodesNumber){
for my $j (1 .. $communitiesNumber){
my $random_number=rand();
if ($prob_comunities > $random_number){
say "$i $j";
}
}
}
This program gives as output a list of two columns of integers as:
1 2
1 4
2 2
2 5
2 7
...
I would like to create a vector in which the first element in the left column is counted once and the right column elements represents the value of the vector's components. I would like the output to look like:
vector[0][0]= 1
vector[0][1]= 2
vector[0][2]= 4
vector[1][0]= 2
vector[1][1]= 2
vector[1][2]= 5
vector[1][3]= 7
Any help?
#!/usr/bin/env perl
# file: build_vector.pl
use strict;
use warnings;
my #vector; # the 2-d vector
my %mark; # mark the occurrence of the number in the first column
my $index = -1; # first dimensional index of the vector
while (<>) {
chomp;
my ($first, $second) = split /\s+/;
next if $second eq '';
if (not exists $mark{$first}) {
$mark{ $first } = ++$index;
push #{ $vector[$index] }, $first;
}
push #{ $vector[$index] }, $second;
}
# dump results
for my $i (0..$#vector) {
for my $j (0..$#{ $vector[$i] }) {
print "$vector[$i][$j] ";
}
print "\n";
}
This script will processing the output of your script and build the vector in #vector. If your script has filename generator.pl, you can call:
$ perl generator.pl | perl build_vector.pl
UPDATE:
use strict;
use warnings;
my $nodesNumber = 100 ;
my $communitiesNumber = 10;
my $prob_communities = 0.3;
my #vector; # the 2-d vector
my %mark; # mark the occurrence of the number in the first column
my $index = -1; # first dimensional index of the vector
for my $i (1 .. $nodesNumber){
for my $j (1 .. $communitiesNumber){
my $random_number=rand();
if ($prob_communities > $random_number){
if (not exists $mark{$i}) {
$mark{ $i } = ++$index;
push #{ $vector[$index] }, $i;
}
push #{ $vector[$index] }, $j;
}
}
}
# dump results
for my $i (0..$#vector) {
for my $j (0..$#{ $vector[$i] }) {
print "$vector[$i][$j] ";
}
print "\n";
}
#!/usr/bin/env perl
use 5.010;
use strict;
use warnings;
use Const::Fast;
use Math::Random::MT;
const my $MAX_RAND => 10;
my $rng = Math::Random::MT->new;
my #v = map {
my $l = $rng->irand;
[ map 1 + int($rng->rand($MAX_RAND)), 0 .. int($l) ];
} 1 .. 5;
use YAML;
print Dump \#v;
I have some code that reads from a file, and outputs the Fibonacchi numbers. E.g: 5 = 1, 1, 2, 3, 5
How can I make my code ONLY print out the last value?
Thanks
#!/usr/bin/perl
use strict;
my $fibFile = shift;
if (!defined($fibFile)) {
die "[*] No file specified...\n";
}
open (FILE, "<$fibFile");
my #numbers = <FILE>;
foreach my $n (#numbers) {
my $a = 1;
my $b = 1;
for (0..($n - 1)) {
print "$a\n";
($a, $b) = ($b,($a + $b));
}
print "\n";
}
close (FILE);
I suggest using a subroutine to take a chunk of code out of the loop
sub fib {
my $n = shift();
my #fib = (1, 1);
push #fib, $fib[-1] + $fib[-2] while #fib < $n;
#fib[0 .. $n-1];
}
for my $n (1 .. 5) {
printf "%d = %s\n", $n, join ', ', fib $n;
}
Do you need to recalculate the Fibonacci series for every value in the file? If not then just move the #fib array declaration outside the subroutine and the data won't need to be recalculated.
I'm sorry I didn't answer the question! To print out only the last value in the sequence, change the loop limit in your code to $n-2 and move the line print "$a\n"; outside the loop to replace the line print "\n";
I have two arrays:
#array1 = (A,B,C,D,E,F);
#array2 = (A,C,H,D,E,G);
The arrays could be of different size. I want to find how many mismatches are there between the arrays. The indexes should be the same. In this case there are three mismatch :b->c,c->h and F->G.(i.e , The 'C' in $array[2] should not be considered a match to 'C' in $array[1]) I would like to get the number of mismatches as well as the mismatch.
foreach my $a1 ( 0 .. $#array1) {
foreach my $a2( 0 .. $#array2)
if($array1[$a1] ne $array2[$a2]) {
}
}
}
my %array_one = map {$_, 1} #array1;
my #difference = grep {!$array_one {$_}} #array1;
print "#difference\n";
Ans: gives me H, G but not C.
with my little Perl knowledge I tried this, with no result. Could you suggest me how I should deal this? Your suggestions and pointers would be very helpful.
You shouldn't have nested loops. You only need to go through the indexes once.
use List::Util qw( max );
my #mismatches;
for my $i (0..max($#array1, $#array2)) {
push #mismatches, $i
if $i >= #array1
|| $i >= #array2
|| $array1[$i] ne $array2[$i];
}
}
say "There are " . (0+#mismatches) . " mismatches";
for my $i (#mismatches) {
...
}
Since you mentioned grep, this is how you'd replace the for with grep:
use List::Util qw( max );
my #mismatches =
grep { $_ >= #array1
|| $_ >= #array2
|| array1[$_] ne $array2[$_] }
0 .. max($#array1, $#array2);
say "There are " . (0+#mismatches) . " mismatches";
for my $i (#mismatches) {
...
}
Here's an example using each_arrayref from List::MoreUtils.
sub diff_array{
use List::MoreUtils qw'each_arrayref';
return unless #_ && defined wantarray;
my #out;
my $iter = each_arrayref(#_);
my $index = 0;
while( my #current = $iter->() ){
next if all_same(#current);
unshift #current, $index;
push #out, \#current;
}continue{ ++$index }
return #out;
}
This version should be faster if you are going to use this for determining the number of differences often. The output is exactly the same. It just doesn't have to work as hard when returning a number.
Read about wantarray for more information.
sub diff_array{
use List::MoreUtils qw'each_arrayref';
return unless #_ && defined wantarray;
my $iter = each_arrayref(#_);
if( wantarray ){
# return structure
my #out;
my $index = 0;
while( my #current = $iter->() ){
next if all_same(#current);
unshift #current, $index;
push #out, \#current;
}continue{ ++$index }
return #out;
}else{
# only return a count of differences
my $out = 0;
while( my #current = $iter->() ){
++$out unless all_same #current;
}
return $out;
}
}
diff_array uses the subroutine all_same to determine if all of the current list of elements are the same.
sub all_same{
my $head = shift;
return undef unless #_; # not enough arguments
for( #_ ){
return 0 if $_ ne $head; # at least one mismatch
}
return 1; # all are the same
}
To get just the number of differences:
print scalar diff_array \#array1, \#array2;
my $count = diff_array \#array1, \#array2;
To get a list of differences:
my #list = diff_array \#array1, \#array2;
To get both:
my $count = my #list = diff_array \#array1, \#array2;
The output for the input you provided:
(
[ 1, 'B', 'C' ],
[ 2, 'C', 'H' ],
[ 5, 'F', 'G' ]
)
Example usage
my #a1 = qw'A B C D E F';
my #a2 = qw'A C H D E G';
my $count = my #list = diff_array \#a1, \#a2;
print "There were $count differences\n\n";
for my $group (#list){
my $index = shift #$group;
print " At index $index\n";
print " $_\n" for #$group;
print "\n";
}
You're iterating over both arrays when you don't want to be doing so.
#array1 = ("A","B","C","D","E","F");
#array2 = ("A","C","H","D","E","G");
foreach my $index (0 .. $#array1) {
if ($array1[$index] ne $array2[$index]) {
print "Arrays differ at index $index: $array1[$index] and $array2[$index]\n";
}
}
Output:
Arrays differ at index 1: B and C
Arrays differ at index 2: C and H
Arrays differ at index 5: F and G
Well, first, you're going to want to go over each element of one of the arrays, and compare it to the same element of the other array. List::MoreUtils provides an easy way to do this:
use v5.14;
use List::MoreUtils qw(each_array);
my #a = qw(a b c d);
my #b = qw(1 2 3);
my $ea = each_array #a, #b;
while ( my ($a, $b) = $ea->() ) {
say "a = $a, b = $b, idx = ", $ea->('index');
}
You can extend that to find where there is a non-match by checking inside that while loop (note: this assumes your arrays don't have undefs at the end, or that if they do, undef is the same as having a shorter array):
my #mismatch;
my $ea = each_array #a, #b;
while ( my ($a, $b) = $ea->() ) {
if (defined $a != defined $b || $a ne $b) {
push #mismatch, $ea->('index');
}
}
and then:
say "Mismatched count = ", scalar(#mismatch), " items are: ", join(q{, }, #mismatch);
The following code builds a list of mismatched pairs, then prints them out.
#a1 = (A,B,C,D,E,F);
#a2 = (A,C,H,D,E,G);
#diff = map { [$a1[$_] => $a2[$_]] }
grep { $a1[$_] ne $a2[$_] }
(0..($#a1 < $#a2 ? $#a1 : $#a2));
print "$_->[0]->$_->[1]\n" for #diff
You have the right idea, but you only need a single loop, since you are looking at each index and comparing entries between the arrays:
foreach my $a1 ( 0 .. $#array1) {
if($array1[$a1] ne $array2[$a1]) {
print "$a1: $array1[$a1] <-> $array2[$a1]\n";
}
}
Having heard about Perl for year I decided to give it a few hours of my time to see how much I could pick up. I got through the basics fine and then got to loops. As a test I wanted to see if I could build a script to recurse through all alphanumerical values of up to 4 characters. I had written a PHP code that did the same thing some time ago so I took the same concept and used it. However when I run the script it puts "a" as the first 3 values and then only loops through the last digit. Anyone see what I am doing wrong?
#!/usr/local/bin/perl
$chars = "abcdefghijklmnopqrstuvwxyz";
$chars .= "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$chars .= "0123456789";
#charset = split(//, $chars);
$charset_length = scalar(#charset);
sub recurse
{
($width, $position, $base_string) = #_;
for ($i = 0; $i < $charset_length; ++$i) {
$base = $base_string . $charset[$i];
if ($position < $width - 1) {
$pos = $position + 1;
recurse($width, $pos, $base);
}
print $base;
print "\n";
}
}
recurse(4, 0, '');
This is what I get when I run it:
aaaa
aaab
aaac
aaad
aaae
aaaf
aaag
aaah
aaai
aaaj
aaak
aaal
aaam
aaan
aaao
aaap
aaaq
aaar
aaas
aaat
aaau
aaav
aaaw
aaax
aaay
aaaz
aaaA
aaaB
aaaC
aaaD
aaaE
aaaF
aaaG
aaaH
aaaI
aaaJ
aaaK
aaaL
aaaM
aaaN
aaaO
aaaP
aaaQ
aaaR
aaaS
aaaT
aaaU
aaaV
aaaW
aaaX
aaaY
aaaZ
aaa0
aaa1
aaa2
aaa3
aaa4
aaa5
aaa6
aaa7
aaa8
aaa9
aaa9
aaa9
aaa9
You've been bitten by non strict scoping, this code does what it should (note the use strict at the top and the subsequent use of my to guarantee variable scoping).
#!/usr/bin/env perl
use strict;
use warnings;
my $chars = "abcdefghijklmnopqrstuvwxyz";
$chars .= "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$chars .= "0123456789";
my #charset = split(//, $chars);
my $charset_length = scalar(#charset);
sub recurse {
my ($width, $position, $base_string) = #_;
for (my $i = 0; $i < $charset_length; ++$i) {
my $base = $base_string . $charset[$i];
if ($position < $width - 1) {
my $pos = $position + 1;
recurse($width, $pos, $base);
}
print $base;
print "\n";
}
}
recurse(4, 0, '');
Already well answered, but a more idiomatic approach would be:
use strict;
use warnings;
sub recurse {
my ($width, $base_string, $charset) = #_;
if (length $base_string) {
print "$base_string\n";
}
if (length($base_string) < $width) {
$recurser->($base_string . $_) for #$charset;
}
}
my #charset = ('a'..'z', 'A'..'Z', '0'..'9');
recurse(4, '', \#charset);
There's no need to pass position; it's implicit in the width of the base string passed in. The charset, on the other hand, should be passed in rather than having the subroutine use an external variable.
Alternatively, since the width and character set stay constant, generate a closure that references them:
use strict;
use warnings;
sub make_recurser {
my ($width, $charset) = #_;
my $recurser;
$recurser = sub {
my ($base_string) = #_;
if (length $base_string) {
print "$base_string\n";
}
if (length($base_string) < $width) {
$recurser->($base_string . $_) for #$charset;
}
}
}
my #charset = ('a'..'z', 'A'..'Z', '0'..'9');
my $recurser = make_recurser(4, \#charset);
$recurser->('');
Alternatively, just:
print "$_\n" for glob(('{' . join(',', 'a'..'z', 'A'..'Z', '0'..'9') . '}') x 4);
It has to do with the scope of the variables, you're still changing the same vars when you're calling the recursion. The keyword 'my' declares the variables local to the subroutine.
(http://perl.plover.com/FAQs/Namespaces.html)
I always use perl with 'use strict;' declared, forcing me to decide on the scope of the variables.
sub recurse {
my ($width, $position, $base_string) = #_;
for (my $i = 0; $i < $charset_length; ++$i) {
my $base = $base_string . $charset[$i];
if ($position < $width - 1) {
my $pos = $position + 1;
recurse($width, $pos, $base);
}
print $base;
print " ";
}
}
You seem to be running into some scoping issues. Perl is very flexible, so it is taking a guess at what you want because you haven't told it what you want. One of the first things you'll learn is to add use strict; as for your first statement after the shebang. It will point out the variables that are not being explicitly defined, as well as any variables that are accessed before being created (helps with misspelled variables, etc).
If you make your code look like this, you'll see why you are getting your errors:
sub recurse {
($width, $position, $base_string) = #_;
for ($i = 0; $i < $charset_length; ++$i) {
$base = $base_string . $charset[$i];
if ($position < $width - 1) {
$pos = $position + 1;
recurse($width, $pos, $base);
}
# print "$base\n";
}
print "$position\n";
}
This should output:
3
3
3
3
Because you are not scoping $position correctly with my, you aren't getting a new variable each recurse, you are re-using the same one. Toss a use strict; in there, and fix the errors you get, and the code should be good.
I realize that you're just tinkering with recursion. But as long as you're having fun comparing implementations between two languages you may as well also see how the CPAN can extend your tool set.
If you don't care about the order, you can generate all 13,388,280 permutations of ( 'a'..'z', 'A..'Z', '0'..'9' ) taken four at a time with the CPAN module, Algorithm::Permute
Here is an example of how that code may look.
use strict;
use warnings;
use Algorithm::Permute;
my $p = Algorithm::Permute->new(
[ 'a' .. 'z', 'A' .. 'Z', '0' .. '9' ], # Set of...
4 # <---- at a time.
);
while ( my #res = $p->next ) {
print #res, "\n";
}
The new() method accepts an array ref that enumerates the character set or list of what to permute. Its second argument is how many at a time to include in the permutation. So you're essentially taking 62 items 4 at a time. Then use the next() method to iterate through the permutations. The rest is just window dressing.
The same thing could be reduced to the following Perl one-liner:
perl -MAlgorithm::Permute -e '$p=Algorithm::Permute->new(["a".."z","A".."Z",0..9],4);print #r, "\n" while #r=$p->next;'
There is also a section on permutation, along with additional examples in perlfaq4. It includes several examples and lists some additional modules that handle the details for you. One of Perl's strengths is the size and completeness of the Comprehensive Perl Archive Network (the CPAN).
I've a set of strings with variable sizes, for example:
AAA23
AB1D1
A1BC
AAB212
My goal is have in alphabetical order and unique characters collected for COLUMNS, such as:
first column : AAAA
second column : AB1A
and so on...
For this moment I was able to extract the posts through a hash of hashes. But now, how can I sort data? Could I for each hash of hash make a new array?
Thank you very much for you help!
Al
My code:
#!/usr/bin/perl
use strict;
use warnings;
my #sessions = (
"AAAA",
"AAAC",
"ABAB",
"ABAD"
);
my $length_max = 0;
my $length_tmp = 0;
my %columns;
foreach my $string (#sessions){
my $l = length($string);
if ($l > $length_tmp){
$length_max = $l;
}
}
print "max legth : $length_max\n\n";
my $n = 1;
foreach my $string (#sessions){
my #ch = split("",$string);
for my $col (1..$length_max){
$columns{$n}{$col} = $ch[$col-1];
}
$n++;
}
foreach my $col (keys %columns) {
print "colonna : $col\n";
my $deref = $columns{$col};
foreach my $pos (keys %$deref){
print " posizione : $pos --> $$deref{$pos}\n";
}
print "\n";
}
exit(0);
What you're doing is rotating the array. It doesn't need a hash of hash or anything, just another array. Surprisingly, neither List::Util nor List::MoreUtils supplies one. Here's a straightforward implementation with a test. I presumed you want short entries filled in with spaces so the columns come out correct.
#!/usr/bin/perl
use strict;
use warnings;
use Test::More;
use List::Util qw(max);
my #Things = qw(
AAA23
AB1D1
A1BC
AAB212
);
sub rotate {
my #rows = #_;
my $maxlength = max map { length $_ } #rows;
my #columns;
for my $row (#rows) {
my #chars = split //, $row;
for my $colnum (1..$maxlength) {
my $idx = $colnum - 1;
$columns[$idx] .= $chars[$idx] || ' ';
}
}
return #columns;
}
sub print_columns {
my #columns = #_;
for my $idx (0..$#columns) {
printf "Column %d: %s\n", $idx + 1, $columns[$idx];
}
}
sub test_rotate {
is_deeply [rotate #_], [
"AAAA",
"AB1A",
"A1BB",
"2DC2",
"31 1",
" 2",
];
}
test_rotate(#Things);
print_columns(#Things);
done_testing;
You can sort the output of %columns in your code with
foreach my $i (sort { $a <=> $b } keys %columns) {
print join(" " => sort values %{ $columns{$i} }), "\n";
}
This gives
A A A A
A A A C
A A B B
A A B D
But using index numbers as hash keys screams that you should use an array instead, so let's do that. To get the columns, use
sub columns {
my #strings = #_;
my #columns;
while (#strings) {
push #columns => [ sort map s/^(.)//s ? $1 : (), #strings ];
#strings = grep length, #strings;
}
#columns;
}
Given the strings from your question, it returns
A A A A
1 A A B
1 A B B
2 2 C D
1 1 3
2
As you can see, this is unsorted and repeats characters. With Perl, when you see the word unique, always think of hashes!
sub unique_sorted_columns {
map { my %unique;
++$unique{$_} for #$_;
[ sort keys %unique ];
}
columns #_;
}
If you don't mind destroying information, you can have columns sort and filter duplicates:
sub columns {
my #strings = #_;
my #columns;
while (#strings) {
my %unique;
map { ++$unique{$1} if s/^(.)//s } #strings;
push #columns => [ sort keys %unique ];
#strings = grep length, #strings;
}
#columns;
}
Output:
A
1 A B
1 A B
2 C D
1 3
2