Re: TIB: program speed

To: ti-basic@lists.ticalc.org
Subject: Re: TIB: program speed
From: Jody <jody1@alaska.net>
Date: Wed, 28 Jan 1998 14:11:33 +0000
References: <19980128200821.16276.qmail@hotmail.com>
Reply-To: ti-basic@lists.ticalc.org


Tavis Segura wrote:
> 
> Yes, when a calculator encounters an If statement with a False boolean,
> it ignores the next command completely.  When you combine the test and
> the function in one line, you run the risk that you can slow the
> calculator down.  I did something similar to that on Aim with the arrow
> keys.  The TI-92 does not treat booleans as 1 or 0 like the other
> calculator, but as a symbol, so such a command would be impossible.  I
> used the keycode to do the following:
> ( -> = store command; (-) = negative symbol)
> 
> While keycode=337 or keycode=340
> sign(keycode-338) -> t
> angle+t -> angle
> If abs(angle)>90
> b[i,2]-181*t -> angle
> PxlText "   ",2,37
> PxlText string(angle),2,55-6*dim(string(angle))
> getKey() -> keycode
> EndWhile
> 
> Here's what it replaced:
> 
> While keycode=337
> PxlText "   ",2,37
> angle-1 -> angle
> angle< (-) 90
> angle+181 -> angle
> PxlText string(angle),2,55-6*dim(string(angle))
> getKey() -> t
> EndWhile
> .
> .
> .
> While keycode=340
> PxlText "   ",2,37
> angle+1 -> angle
> If angle>90
> angle-181 -> angle
> PxlText string(angle),2,55-6*dim(string(angle))
> getKey() -> keycode
> EndWhile
> 
> The numbers 337 and 340 are the keycodes for left and right,
> respectively.  By subtracting 338 from the keycode, I get a negative
> number for left and a positive for right.  The calculator then adds t to
> the angle, decreasing it if it's negative (left) or increasing if it's
> positive (right).
> 
> If the angle ever exceeds 90 degrees in either direction, the t is then
> used to move the angle 180 degrees in the other direction to correct for
> it.  Otherwise it is ignored.  The resulting angle is then displayed on
> the graph as text just before receiving the Getkey command and starting
> all over.
> 
> This method may be slightly slower than the conventional method, but the
> size of the programming is nearly halved.  In the conventional method, I
> would still have to perform the subtraction or addition, so I thought it
> was worth the effort.
> 
> In summation, it is better to make the single line conversion if your
> calculator must do math in both true and false cases.  Otherwise, use
> the test and let it ignore any unnecessarily heavy math.  This is the
> balance all of you program authors must face: speed, power, or
> compactness.
> 
> Tavis
> 
> ______________________________________________________
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Everything you said made sense to me, except up at the top. What do 
you mean the 92 doesn't treat boolean tests as a 0 or 1. Isn't trues 
and falses, 1's and 0's, yeses and no, the entire bases of logic 
statements? What do you mean by "it uses a symbol"?

Jody Snider
jody1@alaska.net

References:

Re: TIB: program speed

From: "Tavis Segura" <tavis@hotmail.com>