# [ncl-talk] commands to handle exponential calculation to return E100 instead of infinity

Rick Brownrigg brownrig at ucar.edu
Wed Apr 26 22:08:21 MDT 2017

```Hi Yi-Chih,

I am not sure what you mean by "...But b12^log(L(j,k))d in the do loop is
not working...".

But hopefully to clarify, NCL is a typed language, so that:

1    ; is an integer
1.   ; is a float
1d  ; is a double
1.d ; is a double

and in general, unless the documentation states otherwise, many functions
in NCL are integer-in/integer-out, float-in/float-out, etc.

So if in your example, "L(j,k)" is a float value, "log(L(j,k))" will be a
float value, and subject to the valid range of floats.  Going back to your
original example:

b10 =  todouble(exp(230.84))

230.84 is a float value, and exp(230.84) will be a float value that happens
to exceed the valid range of floats. To coerce the result to double, you'll
want:

b10 = exp(todouble(230.84))    ;; which is equivalent to "exp(230.84d)"

Hope that helps...
Rick

On Wed, Apr 26, 2017 at 8:27 PM, Yi-Chih Huang <dscpln at gmail.com> wrote:

> Hello,
>
>     The exp(230.84d) is working.  But b12^log(L(j,k))d in the do loop is
> not working.  What would be the command to handle extreme large or extreme
> small numbers in do loop?
>
>     Thanks,
>
>                Yi-Chih
>
>
> On Thu, Apr 27, 2017 at 1:34 AM, Rick Brownrigg <brownrig at ucar.edu> wrote:
>
>> This yields a float result, which is out of range for floats:
>>
>> b10   = exp(230.84)
>> b20   = exp(203.22)
>>
>> Try explicitly making the constants double:
>>
>> b10   = exp(230.84d)
>> b20   = exp(203.22d)
>>
>>
>> On Wed, Apr 26, 2017 at 5:27 AM, Yi-Chih Huang <dscpln at gmail.com> wrote:
>>
>>> Hello,
>>>
>>>     I work on NCL Version 6.1.2.  It said the range of double type is
>>> e-308 - e+307 on https://www.ncl.ucar.edu/Do
>>> cument/Manuals/Ref_Manual/NclDataTypes.shtml.  Although I have tried
>>> several ways, I only got infinity and 8 bits in return.  Could you show me
>>> the command to handle exponential calculation
>>>
>>>
>>> b10   = todouble(exp(230.84))
>>> b20   = todouble(exp(203.22))
>>> b30   = new(1,double,0)
>>> print(b10+"  "+b20+"  "+b30)
>>>
>>> Variable: b30
>>> Type: double
>>> Total Size: 8 bytes
>>>             1 values
>>> Number of Dimensions: 1
>>> Dimensions and sizes:   [1]
>>> Coordinates:
>>>
>>> (0)     inf  inf  inf
>>>
>>> \$ ncl -v
>>> Unknown option `-v'
>>>  Copyright (C) 1995-2013 - All Rights Reserved
>>>  University Corporation for Atmospheric Research
>>>  NCAR Command Language Version 6.1.2
>>>  The use of this software is governed by a License Agreement.
>>>  See http://www.ncl.ucar.edu/ for more details.
>>>
>>>     Thanks much,
>>>
>>>                      Yi-Chih
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> ncl-talk at ucar.edu
>>> List instructions, subscriber options, unsubscribe:
>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>
>>>
>>
>
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