Hey guys, so i've been messing around with the ** command in axe parser to help anyone who may want to figure out how to use it, or at least understand it primitively. so here are 90 minutes worth of observations i've made by testing dozens of axe programs, and then PM'd to quigibo to make sure they're correct observations, which was OK'd.
The ** Command
the documentation reads: "The signed multiplication is performed using the high byte as the integer part and the low byte as the decimal part returning a number in the same format."
here's a quick way to transfer a decimal number into something axe parser will understand. say you wanted to multiply 2.5 and 3.5. That's 8.75, you say, being superb at arithmetic. well, let's see how we can get axe to do it for us: first, break this down starting with the number 2 and one half. second, we take one half. since this is the first 8 bits, which holds the values 0-255, after that point it overflows into the next byte which holds the integer part two. this is better represented in binary:
0 0 0 0 0 0 0 0 | 0 0 0 0 0 0 0 0
32768 16384 8192 4096 2048 1024 512 256 | 128 64 32 16 8 4 2 1
the line separates the high and low bytes. since we want to display one half in the lower byte to the right, we need one half of it. since the lower byte can represent 0-255, or 256 values, to get one half we'll have to divide 256 by two. so we end up with 128. then we need to represent 2 in the higher byte. you'll notice if we divide all the values of the higher byte by 256, they become identical to the lower byte. (32768/256=128, 16384/256=64, etc.) therefore, if we look at the lower byte, figure out what number we're trying to represent (in this case, it's two) and multiply it by 256, we'll get the higher-byte equivalent. which is 2 * 256 so 512. 512+128 = 640. great. we have one number, 2.5. now we need to multiply it by 3.5 do the same thing. what's .5 on our lower-byte scale? 128. and now we add that to 3 * 256, which is 768. total, that's 896. great. now try out this program:
.EXAMPLE
640->A . 2 and a half
896->B . 3 and a half
Disp A**B>Dec
What does it give? it gives 2240. look back at the commands list. it says it will give a number in the same format. therefore, to decode it, all you need to do is divide by 256. you'll notice you get 8.75. which is.. 3.5 * 2.5 (:
so you have a number x, and a number y. and you want to use this program without thinking in binary. here's the quick way, assuming x and y are in base 10 with decimal parts, just multiply them by 256 to get numbers that the ** command understands. 2.5 * 256 = 640, and 3.5 * 256 = 896.
Quigibo also gave me a quick BASIC program that will convert a number from -128 through 128 into 8.8 form (the form Axe reads in).
with the number in Ans:
If Ans<-128 or Ans>128:Then
Disp "OUT OF RANGE
Return
End
Ans+256(Ans<0
256iPart(Ans)+iPart(256fPart(Ans
and Quigibo's way to go from 8.8 back to decimal:
ClrHome
Input "8.8:",A
If A>=2^16
Then
Disp "OUT OF RANGE!"
Stop
End
If A>=2^15:Then
Disp -(2^16-A)/256 . this is a negative, not a minus sign
Else
Disp A/256
End
