Re: Deaf grandma - almost there

On Tue, May 18, 2010 at 11:04 AM, Stephen Hau <[e-mail]> w=
rote:
> From the Chris Pine tutorial for beginners:
>
> **
> Write a Deaf Grandma program. Whatever you say to grandma (whatever
> you type in), she should respond with HUH?! =C2=A0SPEAK UP, SONNY!, unles=
s
> you shout it (type in all capitals). If you shout, she can hear you
> (or at least she thinks so) and yells back, NO, NOT SINCE 1938! To
> make your program really believable, have grandma shout a different
> year each time; maybe any year at random between 1930 and 1950. (This
> part is optional, and would be much easier if you read the section on
> Ruby's random number generator at the end of the methods =C2=A0chapter.)
> You can't stop talking to grandma until you shout BYE.
> Hint: Don't forget about chomp! 'BYE'with an Enter is not the same as
> 'BYE' without one!
> Hint 2: Try to think about what parts of your program should happen
> over and over again. All of those should be in your while loop.
>
> **
> Extend your Deaf Grandma program: What if grandma doesn't want you
> to leave? When you shout BYE, she could pretend not to hear you.
> Change your previous program so that you have to shout BYE three times
> in a row. Make sure to test your program: if you shout BYE three
> times, but not in a row, you should still be talking to grandma.
>
> My code is below, and my question is:
> Why can't I reset the 'byes' count to zero using the 'reset' method I've
> defined?
> I know it works when I change the 'else reset' to 'else byes =3D 0'
>
> byes =3D 0
>
> def didnthear
> =C2=A0puts 'SPEAK UP!'
> end
>
> def heard
> =C2=A0 =C2=A0year =3D (rand(21) + 1930).to_s
> =C2=A0 =C2=A0puts "I heard ya! Not since " + year
> end
>
> def reset
> =C2=A0byes =3D 0
> end
>
> while ( byes < 3 )
> =C2=A0said =3D gets.chomp
>
> =C2=A0if said =3D=3D 'BYE'
> =C2=A0 =C2=A0byes +=3D 1
> =C2=A0else
> =C2=A0 =C2=A0reset
> =C2=A0end
>
> =C2=A0if byes >=3D 3
> =C2=A0 =C2=A0break
> =C2=A0end
>
> =C2=A0if said !=3D said.upcase
> =C2=A0 =C2=A0didnthear
> =C2=A0else
> =C2=A0 =C2=A0heard
> =C2=A0end
> end
>
> puts "heard you 3 times, byeeee"

It doesn't work because of scope.  When you set 'byes =3D 0' in def
reset, you are setting a local variable with scope inside the reset
method.  This is not the same as a local variable in the 'main' scope.

One way to fix this by using an 'instance' scope.  Even though you
aren't technically in a class instance, at some level of abstraction
the default binding is an instance of a class.  So, instead of 'byes'
as a variable, you could use '@byes'.

-Jonathan Nielsen