Hello,


I have questions while reviewing "chron" package(e.g.,chron.R).


1. What is the differences between 3 kinds of function definition ? 
 1) "name" &lt;- function(...
 2) 'name' &lt;- function(...
 3) name &lt;- function(...
Do you know Why  author used various kinds of  definitions ? 
Is there no functional differences between them ? 


2. I don't understand the meaning of the below code:
 
as.chron &lt;- function(x, ...) UseMethod("as.chron")
as.chron.default &lt;- function (x, format, ...)
{ ....


Could you let me know what is role of UseMethod("as.chron") ? 


3. In the following code,



"chron" &lt;-
function(dates. = NULL, times. = NULL,
         format = c(dates = "m/d/y", times = "h:m:s"),
         out.format, origin.)


'dates', 'origin' and 'times' has dot(.) as at the end of word.
Do you know the meaning of dots ? 


4. Could you introduce me some books on S/R language, especially for understanding of generic functions ? 
Some interesting packages such as quantmod, xts, zoo, etc., are seems to be coded using generic functions(UseMethod(..)).
But I can't easily understand the code.


Thanks in advance,




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