Int and Doulbe logical problem.

[exception]

How do you think conditional statements are implemented in a shell?
> tar -xjf myarchive.tar.bz2 && gv content.ps
...would work as little as any loop condition, pipeline etc. if it weren't for values returned from the program.
In the zsh, try
> false
> echo $?
> echo $?
...which will result in the output 1 and then 0, since false returns 1, and echo (if it doesn't fail, which is unlikely) returns 0.

[fudgesticks]

Okay thanks, I got that too. Now, one final question, at least for some time.

I'm learing from C++ for Dummies book. And the definitions they gave for variables and expressions are kind of confusing.

A variable is something that has a value right? But an expression is also something that can have a value. What's the difference between the two?

[Bazzy]

A variable is stored somewhere in the computer memory, an expression is just evaluated:

int v = 5;  // 'v' is a variable with 5 as value
3+2;       // '3+2' is an expression (with 5 as result) but it is not stored
v = 3+2;  // '3+2' is evaluated and the result is assigned to be the value for 'v' 

[fudgesticks]

Another question. I guess these will just keep on coming. :(

I wrote this code:

int Hat = 56;
Hat += 2;
cout << Hat;

int Rat;
cout << "Enter Rat";
cin >> Rat;

Hat = Rat + 2;
cout << Hat;

Now, if I entered "2" for Rat, then the final equation for Hat should be:
56 = 2 + 2 right?
But I don't get this answer. All I get is the value I entered for Rat + 2. Why won't the computer add that answer to 56? Instead all it does is overwrite the original value of Hat, which in this case was 56, and just put in a new value, which would be Rat + 2. Why does it do this? And how can I get past it?

[Bazzy]

If you do something like this: Hat = 2; you are setting the value of Hat to 2.
If you do something like this Hat += 2; you are adding 2 to the previous value of Hat.

So, in Hat = Rat + 2; you are setting Hat to Rat+2

[fudgesticks]

So basically, the original value of Hat gets overwritten? Because in the beginning of the code, I initialized Hat to 56, and then added 2 to it. But later on, I wrote "Hat = Rat + 2".

What I don't understand is, why doesn't the computer store the original value that I put for Hat? Why does it get overwritten during the last part of the code?

[Bazzy]

Because you could want it to be overwritten, if you don't just use += instead of =