[R] 0^0 computation in R : Why it is defined 1 in R ?

[Prof Brian Ripley]

On 26/05/2014 13:16, ritwik_r at isical.ac.in wrote:
> Dear R helpers,
>
>
> today I found something interesting in R. 0^0 gives value 1 in R. But it
> is undefined in mathematics. During debugging a R code, I found it and it
> effects my program severely. So my question is why it is defined 1 in R?
> Is there any particular reason or its a bug in the R software?

Try reading the help:

      Users are sometimes surprised by the value returned, for example
      why ‘(-8)^(1/3)’ is ‘NaN’.  For double inputs, R makes use of IEC
      60559 arithmetic on all platforms, together with the C system
      function ‘pow’ for the ‘^’ operator.  The relevant standards
      define the result in many corner cases.  In particular, the result
      in the example above is mandated by the C99 standard.  On many
      Unix-alike systems the command ‘man pow’ gives details of the
      values in a large number of corner cases.

See §F9.4.4 of the C99 standard.


>
> Here is one demo:
>
> *************************************************
>
> ff=function(u){
>    return( x^0 * u)
> }
>
> x=0
> zz=integrate(ff,lower=0,upper=1)$value
> zz
>
>
>
>> source('~/.active-rstudio-document')
>> zz
> [1] 0.5
>>
>
> *************************************************
>
> Looking forward to hear any response.
>
> Regards,
>
> Ritwik Bhattacharya
> Indian Statistical Institute Kolkata
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
PLEASE do ....


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595