

   VVaalluuee MMaattcchhiinngg

        match(x, table, nomatch=NA)
        x %in% table

   AArrgguummeennttss::

          x: the values to be matched.

      table: the values to be matched against.

    nomatch: the value to be returned in the case when no match
             is found.

   DDeessccrriippttiioonn::

        `match': If `x[i]' is found to equal `table[j]' then
        the value returned in the `i'-th position of the return
        value is `j'.  If no match is found, the value is
        `nomatch'.

        `%in%': A utility function, currently defined as
        `"%in%" <- function(x, y) match(x, y, nomatch = 0) > 0'
        allowing an intuitive usage and returning a logical
        vector of length `length(x)'.

   SSeeee AAllssoo::

        `pmatch' and `charmatch' for (partial) string matching,
        `match.arg', etc for function argument matching.

   EExxaammpplleess::

        ## The intersection of two sets :
        intersect <- function(x, y) y[match(x, y, nomatch = 0)]
        intersect(1:10,7:20)

        1:10 %in% c(1,3,5,9)
        sstr <- c("c","ab","B","bba","c","@","bla","a","Ba","%")
        sstr[sstr %in% c(letters,LETTERS)]

        "%w/o%" <- function(x,y) x[!x %in% y] #--  x without y
        (1:10) %w/o% c(3,7,12)

