tr/// function with variable

[Fafnir956]

I'm trying to make a hangman game and I've run into a specific issue with the tr/// function. I want to replace the letters in the phrase that have not been guessed yet. This code does not work and I know that the highlighted line is the wrong one but I can't figure out how to make it work. Any help will be very appreciated. This is not homework. I am trying to create problems for my student that I tutor. I know there are probably different ways of solving this problem, but I would like to stick with the tr/// operator because it makes the most sense to me.

$Phrase = "I'm trying to find this phrase.";
$guess = "abcde";
print "I already guessed these letters: $guess\n";
$sub=$Phrase;
$alphabet='abcdefghijklmnopqrstuvwxyz';
$alphabet =~ s/$guess//g;
print "These letters should still be hidden: $alphabet\n";
[highlight #FCE94F]$sub =~ tr/$alphabet/\-/;[/highlight]
print "$sub\n";

 

[feherke]

Hi

See Quote and Quote-like Operators in [tt]man perlop[/tt]. It says [tt]tr///[/tt] ( and of course [tt]y///[/tt] ) does not interpolate.

The same manual page proposes a solution later : use eval :

[b]eval[/b] [green][i]"\$sub =~ tr/$alphabet/\-/"[/i][/green][teal];[/teal]

Feherke.
[link feherke.github.com/]

http://feherke.github.com/

[/url]

 

[Fafnir956]

Your code almost worked, but not exactly. It couldn't make sense of the guesses "cba", but it did do "abc". I also had a hard time getting it to be case insensitive with tr///i with the eval function, so I just made a list of the uppercase values and included them in there too. You should test your code before you post it in the future. Thanks for the push in the right direction though.

$Phrase = "I'm trying to find this phrase.";
$guess = "cba";
print "I already guessed these letters: $guess\n";
$sub=$Phrase;
$alphabet='abcdefghijklmnopqrstuvwxyz';
eval"\$alphabet =~ tr/$guess//d";
print "These letters should still be hidden: $alphabet\n";
$ucalph=uc($alphabet);
eval"\$sub =~ tr/$alphabet$ucalph/\-/";
print "$sub\n";

 

[feherke]

Hi

I only answered what you asked : the use of [tt]tr///[/tt] with variable.

If you want a complete solution then better forget [tt]tr///[/tt], it was not invented for what you are using it. Use [tt]s///[/tt] instead :

[navy]$Phrase[/navy] [teal]=[/teal] [green][i]"I'm trying to find this phrase."[/i][/green][teal];[/teal]
[navy]$guess[/navy] [teal]=[/teal] [green][i]"cba"[/i][/green][teal];[/teal]
[b]print[/b] [green][i]"I already guessed these letters: $guess\n"[/i][/green][teal];[/teal]
[navy]$sub[/navy][teal]=[/teal][navy]$Phrase[/navy][teal];[/teal]
[navy]$alphabet[/navy][teal]=[/teal][green][i]'abcdefghijklmnopqrstuvwxyz'[/i][/green][teal];[/teal]
[navy]$alphabet[/navy] [teal]=~[/teal] [highlight][b]s[/b][fuchsia]/[\Q$guess\E]//[/fuchsia][b]gi[/b][/highlight][teal];[/teal]
[b]print[/b] [green][i]"These letters should still be hidden: $alphabet\n"[/i][/green][teal];[/teal]
[navy]$sub[/navy] [teal]=~[/teal] [highlight][b]s[/b][fuchsia]/[\Q$alphabet\E]/-/[/fuchsia][b]gi[/b][/highlight][teal];[/teal]
[b]print[/b] [green][i]"$sub\n"[/i][/green][teal];[/teal]

BTW, unless stated otherwise, I always test the codes I post. But of course, only for the input provided in the question.


Feherke.
[link feherke.github.com/]

http://feherke.github.com/

[/url]