Locked [C] Type Ambiguous Stack

[Breaker]

Alright, I hate that big A word, so we will just call this a typeless stack. In C++ it was really simple, here on the other hand it is not so much. What are the pros and cons of using a typeless stack?

 

Pros:

Multiple data types

Can use multiple data types on the same stack

Easy way to manipulate data

Works same way as system stack

 

Cons:

Annoying at times

Difficult to manage

More math involved

 

So, let's get started with some structures. This tutorial assumes you know math, basic C, and pointers (as well as pointer arithmetic), if you do not please learn (or at least read) that before continuing.

 

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Now, here is where it's really cool. We actually don't need to use a structure. Remember the SP is the only thing we use, and the programmer needs to ensure his stack is balanced at all times. If we keep these assumptions (we do), then all we need is a single pointer.

 

Code:

typedef void* Stack;

 

But why even bother? Why not just use void *'s directly? Well, just for now we will use the typedef, for simplicity.

 

Stack.h:

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Now, why do we have that extra pointer?

Well, if we assign it, we would be changing the value inside the function, but we just have a copy of that value (the address, for the trolls out there) so changing it will just result in a memory leak. If we have an address to the memory location storing the address, we can change it (double-pointer, or pointer-to-pointer).

 

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Yeah, pointless one-liner, I will make this cleaner later on (you will see)

 

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And even that is pretty small. Why are the functions so much smaller?

Simple: it is a VERY basic type we are dealing with, and now we are hardly dealing with data at all.

 

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And finally the most simple one:

 

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But the question I ask myself is WHY IS THIS EVEN A C FILE... It just doesn't have enough crap there for me... I would rather use macros:

 

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Now, we don't need to use double-pointers. If you notice, it is just a few things actually going on here. Some of our more advanced readers will probably be writing programs without these macros.

 

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Isn't that neat? For some this may be too basic, but for others a stepping ground.