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maths problem

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Topic: maths problem (Read 465 times)

hammerjit
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Posts: 26

Re: maths problem
« Reply #2 on: Apr 21^st, 2015, 07:34am »

so how do I apply it in my example code? is there a possible way?

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tsh73
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Re: maths problem
« Reply #3 on: Apr 21^st, 2015, 08:46am »

Code:

precision = 1e-5

hkval = 50000*.60

valueD = hkval/1000

valueC = int(valueD)


if valueC < valueD-precision then
   print "definitely less"
else
    print "approximately same or more"
end if

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hammerjit
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Re: maths problem
« Reply #4 on: Apr 21^st, 2015, 08:53am »

thank you so much....that really helped!!!
grin

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Richard Russell
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Posts: 1348

Re: maths problem
« Reply #5 on: Apr 21^st, 2015, 09:09am »

on Apr 21^st, 2015, 07:34am, hammerjit wrote:

so how do I apply it in my example code? is there a possible way?

What is the problem you are trying to solve? Your code, as it stands, appears to be trying to check whether or not valueD is an integer. It is giving the correct result, because in this case valueD is actually:

Code:

30.00000000000000000173472347597680709441192448139190673828125

(for the reason Anatoly explained).

LBB performs its floating-point calculations to considerably greater accuracy than JB or LB (about 19 significant figures compared with about 16) but small differences of this kind are unavoidable unless you use only integer arithmetic.

Richard.

« Last Edit: Apr 21^st, 2015, 5:49pm by Richard Russell »

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Richard Russell
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Re: maths problem
« Reply #6 on: Apr 21^st, 2015, 2:52pm »

Here's a good illustration of why you have to be careful. Make a small change to the program: change 0.60 to 0.56 as follows:

Code:

hkval = 50000*.56

valueD = hkval/1000

valueC = int(valueD)


if valueC < valueD then
   print "less"
else
    print "same or more"
end if

Now the program reports "less" when run in JB and "same or more" when run in LBB - in other words the opposite of the earlier results!

Richard.

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hammerjit
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Posts: 26

Re: maths problem
« Reply #7 on: Apr 22^nd, 2015, 06:23am »

yes Richard, I understand it now. Thanks again

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