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consider turtle-reported vs. expected-calculated state

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Scott Richmond 2024-07-21 16:26:56 -04:00
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turtle-graphics.md
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@ -67,8 +67,15 @@ But Ludus sending things to its output streams should only cause Ludus panics wh
For pen-and-paper turtles, we don't have RGBA colors. For pen-and-paper turtles, we don't have RGBA colors.
Colors should also be specifiable with strings corresponding to CSS basic colors: black, silver, gray, white, maroon, red, purple, fuchsia, green, lime, olive, yellow, navy, blue, teal, and aqua. Colors should also be specifiable with strings corresponding to CSS basic colors: black, silver, gray, white, maroon, red, purple, fuchsia, green, lime, olive, yellow, navy, blue, teal, and aqua.
**Turtles should maybe communicate states.** **Turtles should communicate states.**
Ludus should have access to turtle states. Ludus should have access to turtle states.
This is important for push/pop situations that we use for L-systems. This is important for push/pop situations that we use for L-systems.
There are two ways to do this: Ludus does its own bookkeeping for turtle states, or it has a way to get the state from a turtle. There are two ways to do this: Ludus does its own bookkeeping for turtle states, or it has a way to get the state from a turtle.
The latter has the value of being instantaneous, and gives us an _expected_ state of the turtle after the commands are all processed.
In particular, this will be necessary for the recursive L-systems that require pushing and popping turtle state.
The latter has the drawback of potentially allowing the turtle state and expected turtle state to fall out of synch.
The former has the value of always giving us the correct, actual state of the turtle.
It has the drawback of requiring such state reporting to be asynchronous, and perhaps wildly asynchronous, as things like moving robots and plotters will take quite some time to actually draw what Ludus tells it to.
(Being able to wait until `eq? (expected, actual)` to do anything else may well be extremely useful.)
That suggests, then, that both forms of turtle state are desirable and necessary.
Thus: turtles should communicate states (and thus there ought to be a protocol for communicating state back to Ludus) and Ludus should always do the bookkeeping of calculating the expected state.