[TI BASIC] Optimizing

[DarkerLine]

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:Repeat Ans=21
:GetKey
:End

This might work, if my basic memories are good (assuming Ans != 21 before this)

Since it's a repeat loop, it doesn't matter if Ans is 21 before it. Not that it matters *points to kalan's post*

If you want to wait for more than one key,

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Repeat max(getKey={21,105
End

or if you want to know which key was pressed afterwards,

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Repeat max(Ans={21,105
getKey
End

and the keypress will be stored in Ans afterwards.

[waeV]

I don't know if something like this has been posted, but I used this in my Tron Basic program and it sped up quite a lot:

instead of

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getkey -> g
if g = 24
then
...
end
if g = 25
then
...
end

I did this

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getkey -> g
if g != 0
if g = 24
then
...
end
if g = 25
then
...
end
end

The only problem is that the game slows down when you hold a key, as it goes through all the if statements.

[tr1p1ea]

Some people optimise their keypress blocks depending on what you need to do. If you only need to increase/decrease an x/y you can just factor in key checks.

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getKey->K
X+(K=26)-(K=24)->X
Y+(K=34)-(K=25)->Y

[waeV]

Huh, I didn't know you could do that. How would you get it to continue in the direction of the keypress without needing to be held down?

[tr1p1ea]

Guess you could:

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getKey
If Ans:Ans->K
X+(K=26)-(K=24)->X
Y+(K=34)-(K=25)->Y

[waeV]

Awesome, that works and keeps the speed fast even when a key is held.

However, I had no idea something like this could be done and still barely understand : does. Where can I read up on this sort of stuff?

I also wanted a variable F that switches between -1 and 1 when 2nd is pressed, an I came up with the following code:

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F * ( -2 * (K=21) + 1) -> F

Oh wait, when I do that it keeps putting 21 in as the last pressed key instead of the direction. Hmm...

[tr1p1ea]

You could try:

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getKey
If Ans and Ans!=21:Ans->K
F*(-2*(Ans=21)+1)->F
X+(K=26)-(K=24)->X
Y+(K=34)-(K=25)->Y

[waeV]

Well, now it won't accept 2nd as input.

Does the ":" equate to a "then"?

[tr1p1ea]

: is the character ':', accessed via Alpha+'.' also the " and " is accessed via 2nd+MATH>LOGIC.

[kalan_vod]

The ":" is just as if you make a new line, but this just helps when you want to group routines in one area. It is not any faster/slower than creating a new line, it really is just a matter of opinion..I love to use it, as it makes things easier to read.

If you are wanting to know more about basic, I would suggest going to TI|BD.

[waeV]

Thanks for the link.

I am confused, though, I am used to the following syntax:

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if ans != 0 and ans !=21
then
ans -> k
end

If : is just the same as a new line, then what how come the following doesn't need a then, an end, or a logic operator for the first comparison?

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if ans and ans != 21:ans -> k

[calc84maniac]

"If" only needs a "Then" and "End" if it needs more than one line of code to run if true (colon counts as a newline).

[waeV]

Well that make for much cleaner code, thanks. I remember you could do something like that in QBASIC but not in Ti-Basic.

So are the following equivalent?

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if ans

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if ans != 0

[benryves]

Non-zero is implicitly true.

[waeV]

Ah, I get it.

Sweet, this will help a ton.