R/utils-collapse.R

In decisionpatterns/cache: Intuitive and Comprehensive Cache

# This is taken from base.tools::collapse 

# Collapse *vector* to a *string*.
#
# Collapses a vector (coercing to character if necessary) into a string.
#
# @param x  R objects to be collapsed, converting to character vectors as
# necessary.
# @param sep an optional character string to separate the results.
#
# @details
# This is implemented as
#   \code{ Reduce( function(x,y) paste(x,y, sep=sep), x ) }
#
# and is different from paste as this operates on a single vector rather than
# a list of vectors.
#
# @seealso
#   [base::paste()] or [base::paste0()] with argumetn `collapse=''`
#   \code{\link[base]{paste0}} with \code{collapse=""}
#   (Why is this different than paste?)
#
# @examples
#
#  collapse( letters )
#  collapse( letters, sep=" ")
#  collapse( letters, ", " )
#  collapse_comma( letters )
#
#  \dontrun{
#    collapse( 'a', 'b', 'c' )  # error
#  }
#
# @keywords manip
# @export

collapse <- function( x, sep='' ) UseMethod('collapse')

# @export
collapse.default <- function( x, sep='' )
  collapse( as.character(x), sep=sep )


# @export
collapse.character <- function( x, sep='' )
  Reduce( function(x,y) paste(x,y, sep=sep), x )


# @details
# `collapse_comma()` uses a sep argument of '`, `' (commma and a space). This
# is mostly useful for pretty printing and code legibility.
#
# @rdname collapse
# @export

collapse_comma <- function(x)
  collapse( x, sep=", ")