J9 has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I have a REALLY newbie question. I want to ask a question from the cmd line and get the answer in. But I want to validate the answer. I have this so far but it seems like far to many lines for what should be a simple thing. 
#! perl.exe
print "Please enter you name:\n";
chomp ($name =<STDIN>);

&answer();
exit;

sub answer()
{

print "Hello $name.\nWill you be joining me for a swim? [Y/N] \n";
chomp ($_=<STDIN>);
    
if (/^[yn]/i)
    {
        if (/^n/i) 
            { 
                print "Begone, evil peon!\n"
            } 
        if (/^y/i)
            {
                print "YIPPEEE.!!!!\n";
            }
    } else {
        # Validate user input and return message if invalid
    print "\n\n=====================================\n";
        print "You Have Entered and Incorrect Option\n";
        print "Valid Options are [Y/N]\n";
        print "=====================================\n\n";
        &answer;
    }
}

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My above code also validates Yesterday as true and never as false. I only want to match [Yy]es, [Nn]o or just [Yy] or [Nn].

Replies are listed 'Best First'.
Re: Yes No Validation
by chromatic (Archbishop) on Feb 06, 2003 at 18:16 UTC

    Ask for them in your regex. 

    if (/^((?:[Yy](?:es))|([Nn](?:o))$/)
{
     ....
}

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Re: Yes No Validation
by lestrrat (Deacon) on Feb 06, 2003 at 18:18 UTC

    something like this?

       if( /^[Yy](?:es)?$/ ) {
       # do what you do for "yes"
   } elsif( /^[Nn]o?$/ ) {
       # do what you do for "no"
   } else {
       # error
   }

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Re: Yes No Validation
by steves (Curate) on Feb 06, 2003 at 18:19 UTC

    Your regexps are matching anything that starts with 'y' or 'n' (any case). Just expand and anchor the matches to look like this: 

    if (/^y|yes|n|no$/i)
    {
        if (/^no?$/i) 
            { 
                print "Begone, evil peon!\n"
            } 
        if (/^y(es)?$/i)
            {
                print "YIPPEEE.!!!!\n";
            }
    } else {
        # Validate user input and return message if invalid
    print "\n\n=====================================\n";
        print "You Have Entered and Incorrect Option\n";
        print "Valid Options are [Y/N]\n";
        print "=====================================\n\n";
        &answer;
    }

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[d/l]

      That first Regexp will fart. See, the way it's written, it will match either a 'y' at the beginning of the string, a 'yes' or 'n' anywhere in the string, or a 'no' at the end. You need to put parens around the patterns to isolate them from the anchors. Also, I'd prefer an elsif to nested ifs: 

      if (/^(y|yes)$/i)
    {
        print "YIPPEEE.!!!!\n";
    }
elsif (/^(n|no)$/i) 
    { 
        print "Begone, evil peon!\n"
    } 
else 
    {
    # Validate user input and return message if invalid
    print "\n\n=====================================\n";
    print "You Have Entered and Incorrect Option\n";
    print "Valid Options are [Y/N]\n";
    print "=====================================\n\n";
    &answer;
    }

      [download]

      However, I would much prefer to use a for as a switch case: 

      SWITCH: for ($input) {
    /^(y|yes)$/i && do {
        print "YIPPEEE.!!!!\n";
        last SWITCH;
        };
    /^(n|no)$/i && do {
        print "Begone, evil peon!\n";
        last SWITCH;
        };
    # Validate user input and return message if invalid
    print "\n\n=====================================\n";
    print "You Have Entered an Incorrect Option\n";
    print "Valid Options are [Y/N]\n";
    print "=====================================\n\n";
    &answer;
}

      [download]

      LAI
      :eof
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Re: Yes No Validation
by Three (Pilgrim) on Feb 07, 2003 at 14:28 UTC

    I am putting a sub from a program that I wrote called Program Archiver.

    This is a generic question answering subroutine

    Here is the sub and some examples.

    #Useage
#Plain yes/no
if (stdin_question() =~ /yes/) { #Do something }

#Y or N
if (stdin_question('y,n','(Y)es (N)o') =~ /y/) { #Do something }

#On or off
if (stdin_question("on,off","(on or off) :",1) =~ /on/) { #Do somethin
+g }

#Advanced useage
$ret = stdin_question("subdir,manual,none","(subdir, manual, none) :")
+;

#Test return value and do somthing





#---------------------------------------------------------------------
+-------------
#    STDIN_QUESTION
#
#    If no arguments assume yes and no answers.  returns a y or n
#
#    $options         Holds the list of valid options.
#    $text        Hold the text to be displayed.
#    $full_match    Tests for full match
#
#---------------------------------------------------------------------
+-------------
sub stdin_question {
    #Get arguments
    my ($options,$text,$match) = @_;    #Get passed in var

    #Varables
    my $input;
    my $flag = 0;
    my @valid_options;

    #Check for defintion of options
    if (!defined($options)) {
        $options = "yes,no";
    }

    #Check for defintion of text
    if (!defined($text)) {
        $text = "(yes or no) :";
    }

    #Check for defination of match
    if (!defined($match)) {
        $match = 0;
    }

    #Put options in an arry
    @valid_options = split/,/, $options;

    #While no match loop
    while ($flag ne 1) {
        #Print out std text
        print $text;

        #Read and chomp stdin
        $input = <stdin>;
        chomp $input;

        #Loop through arry for match
        foreach (@valid_options) {
            #Test forback match
            if (/$input/i) {
                #Test for full match to compare on length
                if ($match eq 1) {
                    if (length($_) eq length($input)) {
                        $flag = 1;
                    }
                } else {
                    $flag = 1;
                }
            }
        }
    }

    #Return answer
    return lc $input;
}

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