From: venkatesh Peddi <venkat.peddi@...>
Date: 2009-09-10T12:50:57+09:00
Subject: Re: How Are Variables Kept Independent of Each Other Yet Pass Values?

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the easy way is you can have another temp variable to which u have to assig=
n the old value.and assing the temp value to new. in this case when u chang=
e the new the temp will change but not old.

=20

temp var =3D old var

new var =3D temp var

// here u can do what ever u want on new. unless u directly change any thin=
g on temp ur old var is safe.

=20

ps:this is a work around=2C i dont recommend it.

=20

=20

-V
=20
> Date: Thu=2C 10 Sep 2009 12:24:05 +0900
> From: masonkelsey@gmail.com
> Subject: How Are Variables Kept Independent of Each Other Yet Pass Values=
?
> To: ruby-talk@ruby-lang.org
>=20
> Somewhere in the several books I've been learning Ruby from there was the
> note that when you create a new variable and assign it a value from anoth=
er
> variable that you really haven't created an independent variable at all b=
ut
> just another name for the source variable. So if you code "new_var =3D
> old_var" the new_var simply points to the location of the value for
> old_var. Consequently=2C if you change one variable=2C you have changed b=
oth.
> I've tested this and it appears to be true. I've made bold the crucial pa=
rt
> of the code.
>=20
> In the following code verifies that variables are not independent in
> assignments:
>=20
> # Test to Determine how 2 Dimentional Arrays Work
> current_state =3D [[1=2C 3=2C 6]=2C [5=2C 0=2C 2]=2C [4=2C 7=2C 8]]
> #new_state =3D [[1=2C 3=2C 6]=2C [5=2C 0=2C 2]=2C [4=2C 7=2C 8]]
> *new_state =3D current_state*
> puts "Current State =3D " + current_state.to_s
> puts "current_state[1][1] is " + current_state[1][1].to_s
> puts "current_state[2][1] is " + current_state[2][1].to_s
> # Exchange positions
> new_state[1][1] =3D current_state[2][1]
> new_state[2][1] =3D current_state[1][1]
> # Show changed values
> puts "New State[1][1] =3D " + new_state[1][1].to_s
> puts "New State[2][1] =3D " + new_state[2][1].to_s
>=20
> Gives the results:
>=20
> >ruby Simple_Test_Class_EightPuzzle.rb
> Current State =3D 136502478
> current_state[1][1] is 0 *<=3D=3D Values before the change*
> current_state[2][1] is 7 *<=3D=3D Values before the change*
> *New State[1][1] =3D 7 <=3D=3D Values after the change
> New State[2][1] =3D 7 <=3D=3D Values after the change. Due to new_state a=
nd
> current_state pointing to the same value.
> *>Exit code: 0
>=20
> Which would only happen if new_state and current_state point to the same
> value!
>=20
> If I execute the code with the above bold line commented out and the comm=
ent
> line above it executed=2C then the exchange occurs properly because new_s=
tate
> and current_state are two independent variables. Thus=2C
>=20
> # Test to Determine how 2 Dimentional Arrays Work
> current_state =3D [[1=2C 3=2C 6]=2C [5=2C 0=2C 2]=2C [4=2C 7=2C 8]]
> *new_state =3D [[1=2C 3=2C 6]=2C [5=2C 0=2C 2]=2C [4=2C 7=2C 8]]
> *#new_state =3D current_state
> puts "Current State =3D " + current_state.to_s
> puts "current_state[1][1] is " + current_state[1][1].to_s
> puts "current_state[2][1] is " + current_state[2][1].to_s
> # Exchange positions
> new_state[1][1] =3D current_state[2][1]
> new_state[2][1] =3D current_state[1][1]
> # Show changed values
> puts "New State[1][1] =3D " + new_state[1][1].to_s
> puts "New State[2][1] =3D " + new_state[2][1].to_s
>=20
> produces the desired results=2C as
>=20
> >ruby Simple_Test_Class_EightPuzzle.rb
> Current State =3D 136502478
> current_state[1][1] is 0
> current_state[2][1] is 7
> *New State[1][1] =3D 7
> New State[2][1] =3D 0 <=3D=3D Proper exchange occurred because new_state =
and
> current_state are independent.
> *>Exit code: 0
> Now=2C my problem is that I *must* give new_state the value that current_=
state
> has but keep them independent=2C because I need to save the original
> configuration of values. How do I pass a value to a new variable from a
> source variable yet keep them independent? I'm sure there is a way=2C I j=
ust
> cannot remember where I read it in the books and the indexes are not
> helpful.
>=20
> Thanks in advance!
>=20
> No Sam

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