in reply to Stdin for just numbers.

If you really want to go with this sort of "extended dialog" via stdin, you should check out Term::ReadLine.

Here's one way to structure things so that the coding is easier. (I'm just going with basic usage in this example - the module has various options and extra methods to make things easier for the person who is typing, such as keeping a history of responses, so they can be recalled and reused, etc. Notice that Term::ReadLine strips off the newline characters for you.) 

#!/usr/bin/perl

use strict;
use warnings;
use Term::ReadLine;

my $term = Term::ReadLine->new();
my @prompts = ( "the starting amount",
                "your current age",
                "the age you want to retire",
                "amount deposited per year",
                "the annual interest rate",
                "expected retirement money" );
my %responses;

for my $prompt ( @prompts ) {
    my $response = '';
    until ( $response =~ /^\d+$/ ) {
        $response = $term->readline( "Enter $prompt: " );
        last unless defined( $response );
        if ( $response =~ /\D/ ) {
            warn "Numeric answers only, please.  Try again.\n";
        }
        elsif ( $prompt eq "the age you want to retire" and
                $response < $responses{"your current age"} ) {
            warn sprintf( "We can't change the past. Give me a number 
+> %d\n",
                          $responses{"your current age"} );
            $response = "";
        }
    }
    $responses{$prompt} = $response if ( defined( $response ));
}

printf "\nThank you for your %d answers\n", scalar keys( %responses );
for ( @prompts ) {
    print "  $_ : $responses{$_}\n" if ( exists( $responses{$_} ));
}

[download]
(There are different "flavors" of Term::ReadLine that you can use; your perl version probably has a "default" version that will suit your needs.)

Replies are listed 'Best First'.
Re^2: Stdin for just numbers.
by BillKSmith (Monsignor) on Mar 16, 2015 at 13:30 UTC
    A module is definitely the way to go. I would prefer IO::Prompt::Hooked. It works on all operating systems and provides validation and retry.
    Bill
[reply]

      You could also use IO::Prompter, which I only recently learned about. 

      #!/usr/bin/perl

use strict;
use warnings;
use feature qw/say/;

use IO::Prompter;

my %responses = ();
my @prompts = (
    ["startamount",     "the starting amount",          ""],
    ["startage",        "your current age",             ""],
    ["endage",          "the age you want to retire",   sub { $_ >= $r
+esponses{'startage'} } ],
    ["yearlydeposit",   "amount deposited per year",    ""],
    ["annualinterest",  "the Annual interest rate",     ""],
    ["expectedmoney",   "Expected Retirement Money",    ""],
);

foreach my $prompt (@prompts) {
    $responses{$prompt->[0]} = prompt "Enter $prompt->[1]:", -num => $
+prompt->[2]
}

foreach (sort keys %responses) {
    say "$_: $responses{$_}";
}

      [download]

      There's probably a better way of specifying empty constraints -- though the OP will likely some constraints that goes beyond "it's a number" imposed on most of the input.

[reply]
[d/l]

      ++ for recommending my module (IO::Prompt::Hooked). I actually implemeneted a solution to the OP's question using IO::Prompt::Hooked last night, and it looked (in my opinion) great. ...but it became late, and I was too tired to submit a post around it. :)

      Anyway, this is exactly the sort of thing that IO::Prompt::Hooked aims to simplify.


      Dave

[reply]

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