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hneemann / Digital

A digital logic designer and circuit simulator.
GNU General Public License v3.0
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Should be able to change handedness of splitters. #70

Closed peterb12 closed 6 years ago

peterb12 commented 6 years ago

Splitters can be rotated in any of the 4 cardinal directions. This is good! But consider the attached image, where the user intent is to send wire 3 to the top-most component and the wire 0 to the bottom-most:

screen shot 2017-11-01 at 1 21 36 pm

Ideally the user would be able to preserve the right-facing-ness of the splitter but reorder the direction of the outputs. Logisim allows you to specify which wires in the splitter get which bits. As near as I can tell, Digital does not yet.

(You can actually accomplish what I'm talking about above by rotating the splitter and the inverting the input and output splitting fan-ins and outs, but that's a bit oblique and is not immediately obvious.)

peterb12 commented 6 years ago

EDIT: I just realized that you can also use the output splitting syntax to do this; so in my example, one could write "3-3,2-2,1-1,0-0" and get the desired behavior. But writing "3,2,1,0" is disastrous.

I think the actual change I'm asking for is not in code, but in documentation: I find the paragraph explaining the syntax for the splitting to be confusing.

peterb12 commented 6 years ago

Thank you!

hneemann commented 6 years ago

By the way: what did you define in the And circuit? Why not using the built-in And?

peterb12 commented 6 years ago

Solely as a way of learning the tool - I was essentially going through Chapter 1 of nand2tetris and re-implementing everything 'from scratch', with parts built entirely on NAND. It was also a good excuse to make a 'library' of parts and make sure that I really understood the inclusion/embedding rules before embarking on a larger project.

screen shot 2017-11-01 at 4 14 48 pm

(the "Not" is similarly defined as a nand with one input connected to both inputs.)

hneemann commented 6 years ago

Ok, thats fine! I was afraid you would build the gates with single cmos transistors. Although this is possible, the simulation becomes very slow if hundreds of individual transistors are used. :-)

itoshkov commented 6 years ago

@peterb12 nand2tetris is an amazing experience. Go for it!

I just want to point out that even with its native tools, you start with implementing everything with NAND-gates, but then you are encouraged to use the embedded implementations for larger components because it's much faster. So if you want to implement a full HACK computer in Digital, it's perfectly OK to use the built-in chips.

And now for the shameless plug: If you go this path, you will need to have a compatible display, for which I recently created a custom chip. You can find it here: https://github.com/itoshkov/digital-n2t.