Little steps with 8th

Today I will show you a few more stack operations.

In the following I will always show you an 8th word followed by it's SED (Stack Effect diagram).
Also I will add pictures to enhance the explanation visually.

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drop \ x -- 
The drop word takes an item from TOS (Top Of Stack) and "drops" it. Effectively it just removes that item from the stack.

Stack before drop:                      Stack after drop:

<--- item removed

In the SED we see that x is at TOS before the drop. After the drop it is gone.
In the pictures you see the same pattern. The TOS item (light blue) is removed from TOS.

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2drop \ x y --
The word 2drop does exactly the same as two consecutive drop words.

Stack before 2drop:                    Stack after 2drop:

<---
    2 items removed
<---






Later on in this series I will show you how you could easily define your own words for e.g. 4drop .etc.

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swap \ x y -- y x
This word swaps the two topmost items on the stack.

Stack before swap:                    Stack after swap:

<--->

     2 items swapped
<--->

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over \ x y -- x y x

This word copies the second item on the stack and puts the copy at TOS.

Stack before over:                      Stack after over: 

<-------------------------

                          |

                          |

> item copied to -

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nip \ x y -- y

This word removes the second item from the stack. It is like drop, but then for the second item.

Stack before nip:                        Stack after nip: 

]  middle item
]  removed 

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That should be enough for today.

In the next article I hope to write about a bit more advanced 8th words.

If you follow these tutorials along, you will get a thorough knowledge of the language in the end.

For more information please visit: http://8th-dev.com/

There you can also find a very friendly forum, where the developer himself will answer your questions patiently!

There you can also download a completely free version you can play with!