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#' toggle the sign of an expression
#'
#' @param x expression
#'
#' @details
#'
#' `toggle.sign` changes the sign of an expression for `+` tp `-` and
#' visa-versa.
#'
#' @examples
#'
#' toggle.sign(1:3)
#' toggle.sign( quote(a) )
#' toggle.sign( quote(-a) )
#'
#' exp <- expression( a, -b, -(a-b) )
#' toggle.sign(exp)
#'
#' @export
toggle.sign <- function(x) UseMethod('toggle.sign')
#' @export
toggle.sign.default <- function(x) -x
#' @export
`toggle.sign.(` <- function(x)
toggle.sign( x[[2]] )
#' @export
toggle.sign.call <- function(x) {
elem.deparsed <- deparse(x)
if( substr(elem.deparsed, 1,1 ) == "-" )
substr( elem.deparsed, 1,1) <- " " else
elem.deparsed <- paste0( "-", elem.deparsed )
parse( text=elem.deparsed )[[1]]
}
#' @export
toggle.sign.name <- function(x) {
elem.deparsed <- deparse(x)
if( substr(elem.deparsed, 1,1 ) == "-" )
substr( elem.deparsed, 1,1) <- " " else
elem.deparsed <- paste0( "-", elem.deparsed )
parse( text=elem.deparsed )[[1]]
}
#' @export
toggle.sign.expression <- function(x) {
for( i in 1:length(x) ) {
elem.deparsed <- deparse( x[[i]] )
# Alrea
if( substr(elem.deparsed, 1,1 ) == "-" )
substr( elem.deparsed, 1,1) <- " " else
elem.deparsed <- paste0( "-", elem.deparsed )
x[[i]] <- parse( text=elem.deparsed )[[1]]
}
x
}
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