This page (revision-22) was last changed on 03-Feb-2023 15:21 by Gromit 

This page was created on 14-Mar-2010 18:17 by Carsten Strotmann

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An Introduction to ACTION
An Introduction to ACTION

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At line 11 changed one line
This is the first of a 2-part series that will introduce you to the Action! programming language, using a short example program that draws kaleidoscopic patterns on the screen. There's an old saying about fooling people which, unfortunately, holds true for trying to please people as well. The problem in my case is that different readers have different levels of experience. I hope this series will please all of you at least some of the time.
This is the first of a 2-part series that will introduce you to the Action! programming language, using a short example program that draws kaleidoscopic patterns on the screen. There's an old saying about barling people which, unfortunately, holds true for trying to please people as well. The problem in my case is that different readers have different levels of experience. I hope this series will please all of you at least some of the time.
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!! PROCedures.
! PROCedures.
At line 104 changed one line
!!Walking through.
! Walking through.
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does. This may look very complicated, but it isn't. X&7 computes which bit is to be modified (same as X MOD 8, but much faster). This is used as the index for the ARRAY __m1__. ARRAY __ml__ is declared to contain a set of 8 masks. Each mask represents the bit to be modified for that index. Thus, when m1(X&7) is or'ed into the byte pointed to by __pos__, it sets only the bit to be plotted without affecting the other bits of that byte.
does. This may look very complicated, but it isn't. X&7 computes which bit is to be modified (same as X MOD 8, but much faster). This is used as the index for the ARRAY __m1__. ARRAY __m1__ is declared to contain a set of 8 masks. Each mask represents the bit to be modified for that index. Thus, when m1(X&7) is or'ed into the byte pointed to by __pos__, it sets only the bit to be plotted without affecting the other bits of that byte.
At line 351 changed one line
erases point __X,Y__ on the screen. ARRAY __m2__ is declared to contain 8 masks which, when and’ed with the byte pointed to by __pos__, erase a single bit without effecting the other bits of that byte.
erases point __X,Y__ on the screen. ARRAY __m2__ is declared to contain 8 masks which, when and'ed with the byte pointed to by __pos__, erase a single bit without effecting the other bits of that byte.
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If you haven't followed all of this, don't worry. I didn‘t go into any details about bit-wise operations (& and %) to keep the description brief. You can still enjoy the results {assuming you have an Action! cartridge). You can even use these two PROCs (__Init__ and __Plot__) in other programs that you write yourself.
If you haven't followed all of this, don't worry. I didn't go into any details about bit-wise operations (& and %) to keep the description brief. You can still enjoy the results (assuming you have an Action! cartridge). You can even use these two PROCs (__Init__ and __Plot__) in other programs that you write yourself.
This page (revision-22) was last changed on 03-Feb-2023 15:21 by Gromit  Top