Subject:
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Re: Mindstorms spirit.ocx programming = RCX ASM coding? (fwd)
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 23 Dec 1999 04:42:01 GMT
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Viewed:
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575 times
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In article <199912230400.WAA30840@einstein.ssz.com>, Jim Choate
<ravage@einstein.ssz.com> wrote:
> ----- Forwarded message from Dave Baum -----
>
> From: dbaum@spambgoneenteract.com (Dave Baum)
> Subject: Re: Mindstorms spirit.ocx programming = RCX ASM coding?
> Date: Thu, 23 Dec 1999 02:44:41 GMT
>
> This gets pretty tedious. Here's an example
> taken from the SDK:
>
> PBrickCtrl.If 2, 5, 2, 0, 15 | If (constant) 5 = variable 15 then
> PBrickCtrl.PlayTone 440, 20 | play a 440 Hz tone for 200 ms.
> PBrickCtrl.Else Else
> PBrickCtrl.PlayTone 5000, 10 | play a 5000 Hz. tone with a 100 ms. duration
> PBrickCtrl.EndIf | Close the If...Else...EndIf • control-structure.
>
> I don't know about you, but I'd much rather do something like this:
>
> if (x == 5)
> PlayTone(440, 20);
> else
> PlayTone(5000, 10);
>
> Don't even get me started on how you'd use spirit.ocx to do something • like this:
>
> if (x * 2 < y + 5)
> PlayTone(440, 20);
>
> ----- End of forwarded message from Dave Baum -----
>
> This is why they make pre-processors.
Preprocesors can make things a little less verbose and also assign
readable names to constants. However, its quite another thing to convert
infix notation to function calls or allocate temporary variables.
In my example:
> if (x * 2 < y + 5)
> PlayTone(440, 20);
There isn't a way to ask the RCX to directly compare "x*2" with "y+5".
You must create two temporary variables, then do the assignments to set
them up. I'm not fluent in spirit.ocx, but here's how it would look in
NQC without variable allocation and expression evaluation:
temp1 = x;
temp1 *= 2;
temp2 = y;
temp2 += 5;
if (temp1 < temp2)
PlayTone(440, 20);
Anyway, this is exactly the sort of thing that NQC does for you. I'm not
saying its impossible to write the code in spirit - just that there are
certain things that a compiler can do for you above what spirit provides.
Dave Baum
--
reply to: dbaum at enteract dot com
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