while going over below example from the book, I am not understanding
why/how below program works.
Can someone explain this to me in better way?
what is READER exactly reading from???
and what does print while <READER> do ? I thought all the print happens
during factorial() and fibonacci()
use warnings;
use strict;
my $arg = shift || '10';
pipe(READER,WRITER) or die "Can't open pipe: $!\n";
### pipe(READHANDLE, WRITEHANDLE) ---> first is the name of a
filehandle to read from
### 2nd is filehandle to write to.
IF successful, pipe() returns a true result code
if ( fork == '0' ) {
close READER;
select WRITER; $| = '1';
factorial($arg);
exit 0;
}
if ( fork == '0' ) {
close READER;
select WRITER; $| = '1';
my $result = fibonacci($arg);
exit 0;
}
#parent process closes WRITER and reads from READER
close WRITER;
print while <READER>;
sub factorial {
my $target = shift;
for ( my $result = 1, my $i = 1; $i <= $target; $i++ ) {
print "factorial($i) => ", $result *= $i, "\n";
}
}
sub fibonacci {
my $target = shift;
my ($a,$b) = (1,0);
for ( my $i = 1; $i <= $target; $i++ ) {
my $c = $a + $b;
print "fibonacci($i) => $c\n";
($a,$b) = ($b,$c);
}
}
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