I'm working through Beginning Perl, and I'm stuck on a
particular exercise. The exercise asks me to take a
number from <STDIN> and print all the prime numbers
between 2 and that number. (ch 4, pg 145, #3)
I can take the number from the user and save it in a
scalar.
My solution to listing the numbers between 2 and it,
is to use the range operator on it and 2, and then
store that into an array.
Of course, then all the numbers are squished together.
(How else might I say that?) So my solution is to
"stringify" the array of numbers by putting the array
inside double quotes and assigning it to itself. That
seems to work.
However, when I test it by calling print "$list[3]" or
print "@list" I get an error.
"Use of unitialized value in concatenation (.) or
string at primeNumbers.pl line 18, STDIN line 1."
This makes me think that my array is still acting like
a string, which I don't want.
I thought Perl was supposed to convert numbers to
strings and back when needed, right?
Am I correct in my thinking?
After, assuming that I can get the array into number
form again, I'll work that out later.
I'll show my code, but, if it's ok with you all,
please don't write code for me, but rather, write an
explanation of why my code is wrong or my thinking
wrong. If you think I'm heading in the wrong
direction, please let me know. Thanks.
#!/usr/bin/perl
# primeNumbers.pl
use warnings;
use strict;
my $input;
my @list;
my @primelist;
print "I want you to enter a list of numbers bigger
than 2.\n";
print "To mark the end of your list, enter 0.\n";
print "Enter a number that is bigger than 2:\t";
$input = <STDIN>;
chomp($input);
print "This is your number: $input \n";
@list = (2 .. $input);
print "list first: @list\n";
@list = "@list";
print "list second: @list\n";
print "this is this the fourth element: $list[3]\n";
#foreach (@list)
#{
# if ($_ % 2 == 0)
# {
# unshift(@primelist, $_);
# print "this is the inloop primelist: @primelist\n";
# }
#}
#print "this is the outloop primelist: @primelist\n";
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