Small valued numbers or scientific computing

[John]

Mike,

   I need to dig a bit deeper and perhaps make a test app.  The issue could be a bit more complicated in my case as the math is happening behind a "do" statement.

   There is field in which the user enters what they want to calculate.  I take that and add a "put" and an "into" targeting a destination field where the answer goes.  The now, correctly formatted liveCode, is executed with a "do" statement.  It appears that using a "do" changes things.

    The same thing seems to happen in the message box.  If I enter "put (1234567890123e-10 * 1e-170)" into the message box, I get a result of 0 while "put (1234567890123 * 1)" gives the expected 1234567890123.

    I need the ability to handle function calls (like cos) and save values to variables from the users entry. Perhaps I can manage to cleverly use the format statement in all of this but it might just be simpler to have the really odd, really long, numberFormat statement since it works.

   Thanks for the input, I appreciate the help.

John

   
On Jun 23, 2013, at 7:48 PM, Mike Bonner <bonnmike at gmail.com> wrote:

> Hmm. was just messing with it in the message box.. I'm not a math guy, but
> seems that when using format you shouldn't need to specify the numberformat.
> 
> I did this..  put format("%1.60e",1.23456e-41 * 1e-20)  where 60 is the
> desired precision.  Seems to work, same type of result but you specify the
> precision in the format string rather than having to type 60 # (or however
> many you need)...
> 
> Just changed it based on your most recent mail that popped in.  Used: put
> format("%1.60e",1234567890123e-10 * 1e-170)
> message box shows  (precision 60)
> 1.234567890123000166120503829534102198735876903021159008931759e-168
> 
> (of course just popping it into the message box but still)
> 
> 
> 
> On Sun, Jun 23, 2013 at 8:42 PM, John <john at onechip.com> wrote:
> 
>> Mike,
>> 
>>   Thanks for the tip.  I am using "format" for display purposes so that I
>> get correctly formatted numbers but, unless I use "numberFormat" first,
>> there is not enough precision available from the result of the
>> multiplication and the result is 0.
>> 
>>   It appears that "numberFormat" sets the number of decimal places LC
>> uses to do the math and "Format" formats the results for display.
>> 
>>   Any other thoughts?
>> 
>> Thanks,
>> John
>> 
>> 
>> 
>> 
>> On Jun 23, 2013, at 7:31 PM, Mike Bonner <bonnmike at gmail.com> wrote:
>> 
>>> look at the format function, specifically the "%#.##E" (or e)
>> incantation.
>>> 
>>> 
>>> On Sun, Jun 23, 2013 at 8:20 PM, John <john at onechip.com> wrote:
>>> 
>>>>  It seems odd that I haven't stumbled into this before and I am sure I
>>>> am doing something wrong, I just can't seem to find a better way around
>> the
>>>> issue of working with small numbers.
>>>> 
>>>>  Suppose I want to multiply two small numbers such as: 1.23456e-41 *
>>>> 1e-20.  Unless I am happy with a result of 0, I have to use a really odd
>>>> numberFormat statement such as:
>>>> 
>>>> set the numberformat to "0.##########...############" where " …"
>>>> represents sixty or so '#'
>>>> 
>>>> This seems really odd.  Surely there is a better way to do this.  Can
>>>> someone help?
>>>> 
>>>> Thanks,
>>>> John
>>>> 
>>>> 
>>>> 
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