### xtable package
###
### Produce LaTeX and HTML tables from R objects.
###
### Copyright 2000-2013 David B. Dahl <dahl@stat.byu.edu>
###
### Maintained by David Scott <d.scott@auckland.ac.nz>
###
### This file is part of the `xtable' library for R and related languages.
### It is made available under the terms of the GNU General Public
### License, version 2, or at your option, any later version,
### incorporated herein by reference.
###
### This program is distributed in the hope that it will be
### useful, but WITHOUT ANY WARRANTY; without even the implied
### warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
### PURPOSE.  See the GNU General Public License for more
### details.
###
### You should have received a copy of the GNU General Public
### License along with this program; if not, write to the Free
### Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
### MA 02111-1307, USA
print.xtable <- function(x,
  type = getOption("xtable.type", "latex"),
  file = getOption("xtable.file", ""),
  append = getOption("xtable.append", FALSE),
  floating = getOption("xtable.floating", TRUE),
  floating.environment = getOption("xtable.floating.environment", "table"),
  table.placement = getOption("xtable.table.placement", "ht"),
  caption.placement = getOption("xtable.caption.placement", "bottom"),
  caption.width = getOption("xtable.caption.width", NULL),
  latex.environments = getOption("xtable.latex.environments", c("center")),
  tabular.environment = getOption("xtable.tabular.environment", "tabular"),
  size = getOption("xtable.size", NULL),
  hline.after = getOption("xtable.hline.after", c(-1,0,nrow(x))),
  NA.string = getOption("xtable.NA.string", ""),
  include.rownames = getOption("xtable.include.rownames", TRUE),
  include.colnames = getOption("xtable.include.colnames", TRUE),
  only.contents = getOption("xtable.only.contents", FALSE),
  add.to.row = getOption("xtable.add.to.row", NULL),
  sanitize.text.function = getOption("xtable.sanitize.text.function", NULL),
  sanitize.rownames.function = getOption("xtable.sanitize.rownames.function",
                                         sanitize.text.function),
  sanitize.colnames.function = getOption("xtable.sanitize.colnames.function",
                                         sanitize.text.function),
  math.style.negative = getOption("xtable.math.style.negative", FALSE),
  math.style.exponents = getOption("xtable.math.style.exponents", FALSE),
  html.table.attributes = getOption("xtable.html.table.attributes", "border=1"),
  print.results = getOption("xtable.print.results", TRUE),
  format.args = getOption("xtable.format.args", NULL),
  rotate.rownames = getOption("xtable.rotate.rownames", FALSE),
  rotate.colnames = getOption("xtable.rotate.colnames", FALSE),
  booktabs = getOption("xtable.booktabs", FALSE),
  scalebox = getOption("xtable.scalebox", NULL),
  width = getOption("xtable.width", NULL),
  comment = getOption("xtable.comment", TRUE),
  timestamp = getOption("xtable.timestamp", date()),
  ...)
{
  ## If caption is length 2, treat the second value as the "short caption"
  caption <- attr(x,"caption",exact = TRUE)
  short.caption <- NULL
  if (!is.null(caption) && length(caption) > 1){
    short.caption <- caption[2]
    caption <- caption[1]
  }

  ## Claudio Agostinelli <claudio@unive.it> dated 2006-07-28 hline.after
  ## By default it print an \hline before and after the columns names
  ## independently they are printed or not and at the end of the table
  ## Old code that set hline.after should include c(-1, 0, nrow(x)) in the
  ## hline.after vector
  ## If you do not want any \hline inside the data, set hline.after to NULL
  ## PHEADER instead the string '\\hline\n' is used in the code
  ## Now hline.after counts how many time a position appear
  ## I left an automatic PHEADER in the longtable is this correct?

  ## Claudio Agostinelli <claudio@unive.it> dated 2006-07-28 include.rownames,
  ## include.colnames
  pos <- 0
  if (include.rownames) pos <- 1

  ## Claudio Agostinelli <claudio@unive.it> dated 2006-07-28
  ## hline.after checks
  if (any(hline.after < -1) | any(hline.after > nrow(x))) {
    stop("'hline.after' must be inside [-1, ", nrow(x), "]")
  }

  ## Claudio Agostinelli <claudio@unive.it> dated 2006-07-28
  ## add.to.row checks
  if (!is.null(add.to.row)) {
    if (is.list(add.to.row) && length(add.to.row) == 2) {
      if (is.null(names(add.to.row))) {
        names(add.to.row) <- c('pos', 'command')
      } else if (any(sort(names(add.to.row))!= c('command', 'pos'))) {
        stop("the names of the elements of 'add.to.row' must be 'pos' and 'command'")
      }
      if (is.list(add.to.row$pos) && is.vector(add.to.row$command,
                                               mode = 'character')) {
        if ((npos <- length(add.to.row$pos)) !=
            length(add.to.row$command)) {
          stop("the length of 'add.to.row$pos' must be equal to the length of 'add.to.row$command'")
        }
        if (any(unlist(add.to.row$pos) < -1) |
            any(unlist(add.to.row$pos) > nrow(x))) {
          stop("the values in add.to.row$pos must be inside the interval [-1, ", nrow(x), "]")
        }
      } else {
        stop("the first argument ('pos') of 'add.to.row' must be a list, the second argument ('command') must be a vector of mode character")
      }
    } else {
      stop("'add.to.row' argument must be a list of length 2")
    }
  } else {
    add.to.row <- list(pos = list(),
                       command = vector(length = 0, mode = "character"))
    npos <- 0
  }

  ## Claudio Agostinelli <claudio@unive.it> dated 2006-07-28 add.to.row
  ## Add further commands at the end of rows
  if (type == "latex") {
    ## Original code before changes in version 1.6-1
    ## PHEADER <- "\\hline\n"

    ## booktabs code from Matthieu Stigler <matthieu.stigler@gmail.com>,
    ## 1 Feb 2012
    if(!booktabs){
      PHEADER <- "\\hline\n"
    } else {
      ## This code replaced to fix bug #2309, David Scott, 8 Jan 2014
      ## PHEADER <- ifelse(-1%in%hline.after, "\\toprule\n", "")
      ## if(0%in%hline.after) {
      ##     PHEADER <- c(PHEADER, "\\midrule\n")
      ## }
      ## if(nrow(x)%in%hline.after) {
      ##     PHEADER <- c(PHEADER, "\\bottomrule\n")
      ## }
      if (is.null(hline.after)){
        PHEADER <- ""
      } else {
        hline.after <- sort(hline.after)
        PHEADER <- rep("\\midrule\n", length(hline.after))
        if (hline.after[1] == -1) {
          PHEADER[1] <- "\\toprule\n"
        }
        if (hline.after[length(hline.after)] == nrow(x)) {
          PHEADER[length(hline.after)] <- "\\bottomrule\n"
        }
      }
    }
  } else {
    PHEADER <- ""
  }

  lastcol <- rep(" ", nrow(x)+2)
  if (!is.null(hline.after)) {
    ## booktabs change - Matthieu Stigler: fill the hline arguments
    ## separately, 1 Feb 2012
    ##
    ## Code before booktabs change was:
    ##    add.to.row$pos[[npos+1]] <- hline.after

    if (!booktabs){
      add.to.row$pos[[npos+1]] <- hline.after
    } else {
      for(i in 1:length(hline.after)) {
        add.to.row$pos[[npos+i]] <- hline.after[i]
      }
    }
    add.to.row$command <- c(add.to.row$command, PHEADER)
  }

  if ( length(add.to.row$command) > 0 ) {
    for (i in 1:length(add.to.row$command)) {
      addpos <- add.to.row$pos[[i]]
      freq <- table(addpos)
      addpos <- unique(addpos)
      for (j in 1:length(addpos)) {
        lastcol[addpos[j]+2] <- paste(lastcol[addpos[j]+2],
                                      paste(rep(add.to.row$command[i],
                                                freq[j]),
                                            sep = "", collapse = ""),
                                      sep = " ")
      }
    }
  }

  if (length(type)>1) stop("\"type\" must have length 1")
  type <- tolower(type)
  if (!all(!is.na(match(type, c("latex","html"))))) {
    stop("\"type\" must be in {\"latex\", \"html\"}")
  }
  ## Disabling the check on known floating environments as many users
  ## want to use additional environments.
  ##    if (!all(!is.na(match(floating.environment,
  ##                          c("table","table*","sidewaystable",
  ##                            "margintable"))))) {
  ##        stop("\"type\" must be in {\"table\", \"table*\", \"sidewaystable\", \"margintable\"}")
  ##    }
  if (("margintable" %in% floating.environment)
      & (!is.null(table.placement))) {
    warning("margintable does not allow for table placement; setting table.placement to NULL")
    table.placement <- NULL
  }
  if (!is.null(table.placement) &&
      !all(!is.na(match(unlist(strsplit(table.placement,  split = "")),
                        c("H","h","t","b","p","!"))))) {
    stop("\"table.placement\" must contain only elements of {\"h\",\"t\",\"b\",\"p\",\"!\"}")
  }
  if (!all(!is.na(match(caption.placement, c("bottom","top"))))) {
    stop("\"caption.placement\" must be either {\"bottom\",\"top\"}")
  }

  if (type == "latex") {
    BCOMMENT <- "% "
    ECOMMENT <- "\n"
    ## See e-mail from "John S. Walker <jsw9c@uic.edu>" dated 5-19-2003
    ## regarding "texfloat"
    ## See e-mail form "Fernando Henrique Ferraz P. da Rosa"
    ## <academic@feferraz.net>" dated 10-28-2005 regarding "longtable"
    if ( tabular.environment == "longtable" & floating == TRUE ) {
      warning("Attempt to use \"longtable\" with floating = TRUE. Changing to FALSE.")
      floating <- FALSE
    }
    if ( floating == TRUE ) {
      ## See e-mail from "Pfaff, Bernhard <Bernhard.Pfaff@drkw.com>"
      ## dated 7-09-2003 regarding "suggestion for an amendment of
      ## the source"
      ## See e-mail from "Mitchell, David"
      ## <David.Mitchell@dotars.gov.au>" dated 2003-07-09 regarding
      ## "Additions to R xtable package"
      ## See e-mail from "Garbade, Sven"
      ## <Sven.Garbade@med.uni-heidelberg.de> dated 2006-05-22
      ## regarding the floating environment.
      BTABLE <- paste("\\begin{", floating.environment, "}",
                      ifelse(!is.null(table.placement),
                             paste("[", table.placement, "]", sep = ""),
                             ""), "\n", sep = "")
      if ( is.null(latex.environments) ||
           (length(latex.environments) == 0) ) {
        BENVIRONMENT <- ""
        EENVIRONMENT <- ""
      } else {
        BENVIRONMENT <- ""
        EENVIRONMENT <- ""
        if ("center" %in% latex.environments){
          BENVIRONMENT <- paste(BENVIRONMENT, "\\centering\n",
                                sep = "")
        }
        for (i in 1:length(latex.environments)) {
          if (latex.environments[i] == "") next
          if (latex.environments[i] != "center"){
            BENVIRONMENT <- paste(BENVIRONMENT,
                                  "\\begin{", latex.environments[i],
                                  "}\n", sep = "")
            EENVIRONMENT <- paste("\\end{", latex.environments[i],
                                  "}\n", EENVIRONMENT, sep = "")
          }
        }
      }
      ETABLE <- paste("\\end{", floating.environment, "}\n", sep = "")
    } else {
      BTABLE <- ""
      ETABLE <- ""
      BENVIRONMENT <- ""
      EENVIRONMENT <- ""
    }

    tmp.index.start <- 1
    if ( ! include.rownames ) {
      while ( attr(x, "align", exact = TRUE)[tmp.index.start] == '|' )
        tmp.index.start <- tmp.index.start + 1
      tmp.index.start <- tmp.index.start + 1
    }
    ## Added "width" argument for use with "tabular*" or
    ## "tabularx" environments - CR, 7/2/12
    if (is.null(width)){
      WIDTH <-""
    } else if (is.element(tabular.environment,
                          c("tabular", "longtable"))){
      warning("Ignoring 'width' argument.  The 'tabular' and 'longtable' environments do not support a width specification.  Use another environment such as 'tabular*' or 'tabularx' to specify the width.")
      WIDTH <- ""
    } else {
      WIDTH <- paste("{", width, "}", sep = "")
    }

    BTABULAR <-
      paste("\\begin{", tabular.environment, "}",
            WIDTH, "{",
            paste(c(attr(x, "align",
                         exact = TRUE)[
              tmp.index.start:length(attr(x, "align",
                                          exact = TRUE))],
              "}\n"),
              sep = "", collapse = ""),
            sep = "")

    ## fix 10-26-09 (robert.castelo@upf.edu) the following
    ## 'if' condition is added here to support
    ## a caption on the top of a longtable
    if (tabular.environment == "longtable" && caption.placement == "top") {
      if (is.null(short.caption)){
        BCAPTION <- "\\caption{"
      } else {
        BCAPTION <- paste("\\caption[", short.caption, "]{", sep = "")
      }
      ECAPTION <- "} \\\\ \n"
      if ((!is.null(caption)) && (type == "latex")) {
        BTABULAR <- paste(BTABULAR,  BCAPTION, caption, ECAPTION,
                          sep = "")
      }
    }
    ## Claudio Agostinelli <claudio@unive.it> dated 2006-07-28
    ## add.to.row position -1
    BTABULAR <- paste(BTABULAR, lastcol[1], sep = "")
    ## the \hline at the end, if present, is set in full matrix
    ETABULAR <- paste("\\end{", tabular.environment, "}\n", sep = "")

    ## Add scalebox - CR, 7/2/12
    if (!is.null(scalebox)){
      BTABULAR <- paste("\\scalebox{", scalebox, "}{\n", BTABULAR,
                        sep = "")
      ETABULAR <- paste(ETABULAR, "}\n", sep = "")
    }

    ## BSIZE contributed by Benno <puetz@mpipsykl.mpg.de> in e-mail
    ## dated Wednesday, December 01, 2004
    if (is.null(size) || !is.character(size)) {
      BSIZE <- ""
      ESIZE <- ""
    } else {
      if(length(grep("^\\\\", size)) == 0){
        size <- paste("\\", size, sep = "")
      }
      ## Change suggested by Claudius Loehnert reported in Bug #6260
      ## BSIZE <- paste("{", size, "\n", sep = "")
      ## ESIZE <- "{\n"
      BSIZE <- paste("\\begingroup", size, "\n", sep = "")
      ESIZE <- "\\endgroup\n"
    }
    BLABEL <- "\\label{"
    ELABEL <- "}\n"
    ## Added caption width (jeff.laake@nooa.gov)
    if(!is.null(caption.width)){
      BCAPTION <- paste("\\parbox{",caption.width,"}{",sep="")
      ECAPTION <- "}"
    } else {
      BCAPTION <- NULL
      ECAPTION <- NULL
    }
    if (is.null(short.caption)){
      BCAPTION <- paste(BCAPTION,"\\caption{",sep="")
    } else {
      BCAPTION <- paste(BCAPTION,"\\caption[", short.caption, "]{", sep="")
    }
    ECAPTION <- paste(ECAPTION,"} \n",sep="")
    BROW <- ""
    EROW <- " \\\\ \n"
    BTH <- ""
    ETH <- ""
    STH <- " & "
    BTD1 <- " & "
    BTD2 <- ""
    BTD3 <- ""
    ETD  <- ""
    } else {
      BCOMMENT <- "<!-- "
      ECOMMENT <- " -->\n"
      BTABLE <- paste("<table ", html.table.attributes, ">\n", sep = "")
      ETABLE <- "</table>\n"
      BENVIRONMENT <- ""
      EENVIRONMENT <- ""
      BTABULAR <- ""
      ETABULAR <- ""
      BSIZE <- ""
      ESIZE <- ""
      BLABEL <- "<a name="
      ELABEL <- "></a>\n"
      BCAPTION <- paste("<caption align=\"", caption.placement, "\"> ",
                        sep = "")
      ECAPTION <- " </caption>\n"
      BROW <- "<tr>"
      EROW <- " </tr>\n"
      BTH <- " <th> "
      ETH <- " </th> "
      STH <- " </th> <th> "
      BTD1 <- " <td align=\""
      align.tmp <- attr(x, "align", exact = TRUE)
      align.tmp <- align.tmp[align.tmp!="|"]
      if (nrow(x) == 0) {
        BTD2 <- matrix(nrow = 0, ncol = ncol(x)+pos)
      } else {
        BTD2 <- matrix(align.tmp[(2-pos):(ncol(x)+1)],
                       nrow = nrow(x), ncol = ncol(x)+pos, byrow = TRUE)
      }
      ## Based on contribution from Jonathan Swinton <jonathan@swintons.net>
      ## in e-mail dated Wednesday, January 17, 2007
      BTD2[regexpr("^p", BTD2)>0] <- "left"
      BTD2[BTD2 == "r"] <- "right"
      BTD2[BTD2 == "l"] <- "left"
      BTD2[BTD2 == "c"] <- "center"
      BTD3 <- "\"> "
      ETD  <- " </td>"
    }

  result <- string("", file = file, append = append)
  info <- R.Version()
  ## modified Claudio Agostinelli <claudio@unive.it> dated 2006-07-28
  ## to set automatically the package version
  if (comment){
    result <- result + BCOMMENT + type + " table generated in " +
      info$language + " " + info$major + "." + info$minor +
      " by xtable " +  packageDescription('xtable')$Version +
                                                  " package" + ECOMMENT
    if (!is.null(timestamp)){
      result <- result + BCOMMENT + timestamp + ECOMMENT
    }
  }
  ## Claudio Agostinelli <claudio@unive.it> dated 2006-07-28 only.contents
  if (!only.contents) {
    result <- result + BTABLE
    result <- result + BENVIRONMENT
    if ( floating == TRUE ) {
      if ((!is.null(caption)) &&
          (type == "html" ||caption.placement == "top")) {
        result <- result + BCAPTION + caption + ECAPTION
      }
      if (!is.null(attr(x, "label", exact = TRUE)) &&
          (type == "latex" && caption.placement == "top")) {
        result <- result + BLABEL +
          attr(x, "label", exact = TRUE) + ELABEL
      }
    }
    result <- result + BSIZE
    result <- result + BTABULAR
  }
  ## Claudio Agostinelli <claudio@unive.it> dated 2006-07-28
  ## include.colnames, include.rownames
  if (include.colnames) {
    result <- result + BROW + BTH
    if (include.rownames) {
      result <- result + STH
    }
    ## David G. Whiting in e-mail 2007-10-09
    if (is.null(sanitize.colnames.function)) {
      CNAMES <- sanitize(names(x), type = type)
    } else {
      CNAMES <- sanitize.colnames.function(names(x))
    }
    if (rotate.colnames) {
      ##added by Markus Loecher, 2009-11-16
      CNAMES <- paste("\\begin{sideways}", CNAMES, "\\end{sideways}")
    }
    result <- result + paste(CNAMES, collapse = STH)

    result <- result + ETH + EROW
  }

  cols <- matrix("", nrow = nrow(x), ncol = ncol(x)+pos)
  if (include.rownames) {
    ## David G. Whiting in e-mail 2007-10-09
    if (is.null(sanitize.rownames.function)) {
      RNAMES <- sanitize(row.names(x), type = type)
    } else {
      RNAMES <- sanitize.rownames.function(row.names(x))
    }
    if (rotate.rownames) {
      ##added by Markus Loecher, 2009-11-16
      RNAMES <- paste("\\begin{sideways}", RNAMES, "\\end{sideways}")
    }
    cols[, 1] <- RNAMES
  }

  ## Begin vectorizing the formatting code by Ian Fellows [ian@fellstat.com]
  ## 06 Dec 2011
  ##
  ##  disp <- function(y) {
  ##    if (is.factor(y)) {
  ##      y <- levels(y)[y]
  ##    }
  ##    if (is.list(y)) {
  ##      y <- unlist(y)
  ##    }
  ##    return(y)
  ##  }
  varying.digits <- is.matrix( attr( x, "digits", exact = TRUE ) )
  ## Code for letting "digits" be a matrix was provided by
  ## Arne Henningsen <ahenningsen@agric-econ.uni-kiel.de>
  ## in e-mail dated 2005-06-04.
  ##if( !varying.digits ) {
  ## modified Claudio Agostinelli <claudio@unive.it> dated 2006-07-28
  ##  attr(x,"digits") <- matrix( attr( x, "digits",exact=TRUE ),
  ## nrow = nrow(x), ncol = ncol(x)+1, byrow = TRUE )
  ##}
  for(i in 1:ncol(x)) {
    xcol <- x[, i]
    if(is.factor(xcol))
      xcol <- as.character(xcol)
    if(is.list(xcol))
      xcol <- sapply(xcol, unlist)
    ina <- is.na(xcol)
    is.numeric.column <- is.numeric(xcol)

    if(is.character(xcol)) {
      cols[, i+pos] <- xcol
    } else {
      if (is.null(format.args)){
        format.args <- list()
      }
      if (is.null(format.args$decimal.mark)){
        format.args$decimal.mark <- options()$OutDec
      }
      if(!varying.digits){
        curFormatArgs <-
          c(list(
            x = xcol,
            format =
              ifelse(attr(x, "digits", exact = TRUE )[i+1] < 0, "E",
                     attr(x, "display", exact = TRUE )[i+1]),
            digits = abs(attr(x, "digits", exact = TRUE )[i+1])),
            format.args)
        cols[, i+pos] <- do.call("formatC", curFormatArgs)
      }else{
        for( j in 1:nrow( cols ) ) {
          curFormatArgs <-
            c(list(
              x = xcol[j],
              format =
                ifelse(attr(x, "digits", exact = TRUE )[j, i+1] < 0,
                       "E", attr(x, "display", exact = TRUE )[i+1]),
              digits =
                abs(attr(x, "digits", exact = TRUE )[j, i+1])),
              format.args)
          cols[j, i+pos] <- do.call("formatC", curFormatArgs)
        }
      }
    }
    ## End Ian Fellows changes

    if ( any(ina) ) cols[ina, i+pos] <- NA.string
    ## Based on contribution from Jonathan Swinton <jonathan@swintons.net>
    ## in e-mail dated Wednesday, January 17, 2007
    if ( is.numeric.column ) {
      cols[, i+pos] <-
        sanitize.numbers(cols[, i+pos], type = type,
                         math.style.negative = math.style.negative,
                         math.style.exponents = math.style.exponents)
    } else {
      if (is.null(sanitize.text.function)) {
        cols[, i+pos] <- sanitize(cols[, i+pos], type = type)
      } else {
        cols[, i+pos] <- sanitize.text.function(cols[, i+pos])
      }
    }
  }

  multiplier <- 5
  full <- matrix("", nrow = nrow(x), ncol = multiplier*(ncol(x)+pos)+2)
  full[, 1] <- BROW
  full[, multiplier*(0:(ncol(x)+pos-1))+2] <- BTD1
  full[, multiplier*(0:(ncol(x)+pos-1))+3] <- BTD2
  full[, multiplier*(0:(ncol(x)+pos-1))+4] <- BTD3
  full[, multiplier*(0:(ncol(x)+pos-1))+5] <- cols
  full[, multiplier*(0:(ncol(x)+pos-1))+6] <- ETD

  full[, multiplier*(ncol(x)+pos)+2] <- paste(EROW, lastcol[-(1:2)],
                                              sep = " ")

  if (type == "latex") full[, 2] <- ""
  result <- result + lastcol[2] + paste(t(full), collapse = "")
  if (!only.contents) {
    if (tabular.environment == "longtable") {
      ## booktabs change added the if() - 1 Feb 2012
      if(!booktabs) {
        result <- result + PHEADER
      }

      ## fix 10-27-09 Liviu Andronic (landronimirc@gmail.com) the
      ## following 'if' condition is inserted in order to avoid
      ## that bottom caption interferes with a top caption of a longtable
      if(caption.placement == "bottom"){
        if ((!is.null(caption)) && (type == "latex")) {
          result <- result + BCAPTION + caption + ECAPTION
        }
      }
      if (!is.null(attr(x, "label", exact = TRUE))) {
        result <- result + BLABEL + attr(x, "label", exact = TRUE) +
          ELABEL
      }
      ETABULAR <- "\\end{longtable}\n"
    }
    result <- result + ETABULAR
    result <- result + ESIZE
    if ( floating == TRUE ) {
      if ((!is.null(caption)) &&
          (type == "latex" && caption.placement == "bottom")) {
        result <- result + BCAPTION + caption + ECAPTION
      }
      if (!is.null(attr(x, "label", exact = TRUE)) &&
          caption.placement == "bottom") {
        result <- result + BLABEL + attr(x, "label", exact = TRUE) +
          ELABEL
      }
    }
    result <- result + EENVIRONMENT
    result <- result + ETABLE
  }
  result <- sanitize.final(result, type = type)

  if (print.results){
    print(result)
  }

  return(invisible(result$text))
}

"+.string" <- function(x, y) {
  x$text <- paste(x$text, as.string(y)$text, sep = "")
  return(x)
}

print.string <- function(x, ...) {
  cat(x$text, file = x$file, append = x$append)
  return(invisible())
}

string <- function(text, file = "", append = FALSE) {
  x <- list(text = text, file = file, append = append)
  class(x) <- "string"
  return(x)
}

as.string <- function(x, file = "", append = FALSE) {
  if (is.null(attr(x, "class", exact = TRUE)))
    switch(data.class(x),
           character = return(string(x, file, append)),
           numeric = return(string(as.character(x), file, append)),
           stop("Cannot coerce argument to a string"))
  if (class(x) == "string")
    return(x)
  stop("Cannot coerce argument to a string")
}

is.string <- function(x) {
  return(class(x) == "string")
}