[R] Which data structure in R can mimic hash in PERL best?

[Wacek Kusnierczyk]

Duncan Temple Lang wrote:
>
> Hans W. Borchers wrote:
>> Below I enclose a solution that I have written some month ago. It is
>> given in pythonic language, but you can easily translate it into the
>> corresponding Perl terms. One drawback is that one cannot use numbers
>> as keys, only keys following the naming conventions for variable names
>> are allowed.
>
> I imagine that you want to add inherits = FALSE
> to calls to exists() and get() in your code or
> else you risk quite unusual semantics of a hash table.

as far as i can see, an alternative is to use empty parent environments:

def.h <- function() new.env(hash=TRUE, parent=emptyenv())


vQ


>
>  D.
>
>>
>> Hans Werner Borchers
>> ABB Corporate Research
>>
>>
>> #-- Define functions on Hash Tuples (Python alike) ---------------------
>>
>> def.h <- function() new.env(hash=TRUE)
>> len.h <- function(dict) length(ls(envir=dict))
>> set.h <- function(key, val, dict) assign(key, val, envir=dict)
>> get.h <- function(key, dict, default=NULL) {
>>     if (exists(key, envir=dict)) { get(key, dict)
>>     } else { default } }
>> has_key <- function(key, dict) exists(key, envir=dict)
>> keys.h <- function(dict) ls(envir=dict)
>> items.h <- function(dict) as.list(dict)
>> values.h <- function(dict, mode='character') {
>>     l <- as.list(dict)
>>     n <- length(l)
>>     if (n==0) invisible(NULL)
>>     v <- vector('character', n)
>>     for (i in 1:n) v[i] <- l[[i]]
>>     if (mode=='numeric') v <- as.numeric(v)
>>     return(v)
>> }
>> del.h <- function(key, dict) {
>>     if (exists(key, envir=dict)) {
>>         val <- get.h(key, dict)
>>         rm(list=c(key), envir=dict)
>>     } else {
>>         val <- NULL
>>     }
>>     invisible(val)
>> }
>> clear.h <- function(dict) {
>>     rm(list=keys.h(dict), envir=dict)
>> }
>> #-----------------------------------------------------------------------
>>
>
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Wacek Kusnierczyk, MD PhD

Email: waku at idi.ntnu.no
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