Possible to assign count to array? like #content.$i? - arrays

Question

my csv input file
Chapter,Content
A,1
B,3
C,1
C,2
C,3
D,5
My current perl script
open(INFILE,$input)||die "can't open the file";
#line = (split/,/,$_);
#line_last = (split/\n/,$line[1]);
if ($_ =~ /A/){
push #con1, $line[1];
}
elsif ($_ =~ /B/){
push #con2, $line[1];
}
elsif ($_ =~ /C/){
push #con3, $line[1];
}
elsif ($_ =~ /D/){
push #con4, $line[1];
}
close INFILE;
chomp #con1, #con2, #con3, #con4;
print "content =", (join ", ", #con1),"\n";
print "content =", (join ", ", #con2),"\n";
print "content =", (join ", ", #con3),"\n";
print "content =", (join ", ", #con4),"\n";
My current code can work but I wanna make my code shorter & more efficient.
How do I make #con more automate? something like using For loop & use $i to assign to #con to make overall code shorter.

Answer 1

Why it's stupid to `use a variable as a variable name'.
You should use an AoA instead.
use Text::CSV_XS qw( );
my $csv = Text::CSV_XS->new({ binary => 1, auto_diag => 2 });
open my $fh, "<", $qfn)
or die("Can't open \"$qfn\": $!\n");
my #foos = qw( A B C D );
my $num_eles = 0;
my %index_by_foo = map { $_ => $num_eles++ } #foos;
my #cons_by_foo = map { [] } 1..$num_eles;
while (my $row = $csv->getline($fh)) {
if ( my $i = $index_by_foo{ $row->[0] } ) {
push #{ $cons_by_foo[$i] }, $row->[1];
}
}
for my $i (1..$num_eles-1) {
print("content =", join(", ", #{ $cons_by_foo[$i] }), "\n");
}
That said, a HoA seems a far better fit.
use Text::CSV_XS qw( );
my $csv = Text::CSV_XS->new({ binary => 1, auto_diag => 2 });
open my $fh, "<", $qfn)
or die("Can't open \"$qfn\": $!\n");
my %cons_by_foo;
while (my $row = $csv->getline($fh)) {
push #{ $cons_by_foo{ $row->[0] } }, $row->[1];
}
for my $foo (sort keys %cons_by_foo) {
print("content $foo =", join(", ", #{ $cons_by_foo{$foo} }), "\n");
}

Answer 2

This is what a hash is great for IMO (hashtable or dictionary in other languages).
note: I haven't tested this code, it's from memory.
my %con;
while (<INFILE>)
{
my #line_last = (split/\n/,$line[1]);
$con{$line[0]} = $con{$line[0]} + ", " + $line[1];
}
foreach my $str (keys sort %con)
{
print "content $con{$str}\n";
}
edit: much better and tested code here.
open(INFILE,"input.txt")||die "can't open the file";
my %con;
while (<INFILE>)
{
next if /^Chapter/;
chomp;
my #line = (split ',' , $_);
push #{$con{$line[0]}}, $line[1];
}
foreach my $str (sort keys %con)
{
my $tmp = join ', ', #{$con{$str}};
print "content $str = $tmp\n";
}
output is:
content A = 1
content B = 3
content C = 1,2,3
content D = 5
I know that isn't your output, but it seems more useful than what you had.

Answer 3

my %cc; #chapter contents
open my $FH, $filename or die "Cannot open $filename";
push #{ $cc{ $$_[0] } }, $$_[1] for map {chomp;[split/,/]} <$FH>;
close $FH;
print "Chapter = $_ Content = " . join(", ", #{ $cc{$_} }) . "\n" for sort keys %cc;
Output:
Chapter = A Content = 1
Chapter = B Content = 3
Chapter = C Content = 1, 2, 3
Chapter = D Content = 5