[R] The meaning of functional language

[Berton Gunter]

'functional'  languages derive from LISP and the lamda-calculus. These are
standard topics in CS computer language courses. You can look them up in
Wikipedia, or Google for other sources.

-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
"The business of the statistician is to catalyze the scientific learning
process."  - George E. P. Box
 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Patrick Burns
> Sent: Tuesday, October 18, 2005 2:40 PM
> To: ronggui
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] The meaning of functional language
> 
> ronggui wrote:
> 
> >It's often heard that the S language is a  functional 
> language.But What's the exact meaning of this termology in 
> the context of S language?
> >  
> >
> 
> Here's the idea. If you have:
> 
> x <- 1:10
> f <- function(y) { x <- sin(y / 2); x + y}
> f(-3:3)
> 
> then the 'x' inside 'f' does not wipe out your top-level 'x'
> when 'f' is called.
> 
> Operationally it means that objects are only changed via
> the assignment operator. (This is not strictly true, but other
> vehicles, such as '<<-', are generally considered bad style.)
> 
> The reason for wanting this behavior is so that you don't need
> to worry about objects getting invisibly changed while you
> are analyzing some data, or whatever it is that you are doing.
> That is, the language was designed to be human efficient, while
> sacrificing some machine efficiency.
> 
> Patrick Burns
> patrick at burns-stat.com
> +44 (0)20 8525 0696
> http://www.burns-stat.com
> (home of S Poetry and "A Guide for the Unwilling S User")
> 
>