Accept user input perl - perl

Question

How do I accept a list of integers as input? The only thing I can think of is getting each integer from the list specifically using STDIN. Is there a better way to do this?

Answer 1

You want input a list of integers? I take it you mean that you want to enter a list of numbers, and accept that input if they're all integers.
In this program, I loop forever until I get a valid list, thus for (;;). Some people prefer while (1).
I use Scalar::Util's looks_like_number to test whether the input is numeric, and then use int to verify that the number is an integer. You could use a regular expression like /^\d+$/, but there's no guarantee that it works in all circumstances. Using int and looks_like_number guarantees the results.
I assume that a list of integers could be space separated or comma separated or both, thus my split /[\s,]+/.
You said:
The only thing I can think of is getting each integer from the list specifically using STDIN. Is there a better way to do this?
You read in data from a file handle, whether a file or something like STDIN. No way around that. However, you can at least make it a single input rather one at a time which I assume you mean.
By the way, I could have combined my numeric test with:
if( not looks_like_number $integer or $integer != $integer ) {
Since this is an or statement, if this would first check if $input looks numeric, and if it isn't, would warn about the input before checking to see if it's an integer. However, I'm not sure this is actually clearer than making it too separate statements.
#! /usr/bin/env perl
#
use strict;
use warnings;
use feature qw(say);
use Scalar::Util qw(looks_like_number);
my #integers; # Storage for my integers
#
# Keep looping until you have a valid input
#
INPUT:
for (;;) {
print "List of integers: ";
my $input = <STDIN>;
chomp $input;
#integers = split /[\s,]+/, $input;
#
# Verify inputted "number" is numeric and an integer
#
for my $integer ( #integers ) {
if( not looks_like_number $integer ) {
warn qq(Invalid number entered: "$integer");
next INPUT;
}
if( $integer != int $integer ) {
warn qq(Invalid integer entered: "$integer");
next INPUT;
}
}
#
# Exit if there's at least one integer in #integers
#
last if #integers;
}
say "Integers: " . join ": ", #integers;

Answer 2

This is how I did it:
$input = 0;
while($input != -1)
{
print "add input, finish with -1", "\n";
$input = <STDIN>;
chomp($input);
push(#array, $input);
}
#You also need to remove the last input, -1, with pop:
pop(#array);
print #array;
Console output:
add input, finish with -1
1
add input, finish with -1
2
add input, finish with -1
-1
12
If the user inputs a tab delimited string of numbers directly,
you can use the splice function to separate the strings.
#array = splice(/\t/,$array[0])

Answer 3

Here's one approach, taking a comma-separated list of integers:
my $input = <STDIN>;
chomp($input);
if ($input !~ m/^(\d+(,\d+)*)?$/) { die('invalid input'); }
my #input = split(/,/, $input );
Or you could read one integer per line:
my #input;
while (my $input = <STDIN>) {
chomp($input);
if ($input !~ m/^\d+$/) { die('invalid input'); }
push(#input, $input );
} ## end while