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# Check whether a symbol is a valid magrittr pipe.
#
# @param pipe A quoted symbol
# @return logical - TRUE if a valid magrittr pipe, FALSE otherwise.
is_pipe <- function(pipe)
{
identical(pipe, quote(`%>%`)) ||
identical(pipe, quote(`%T>%`)) ||
identical(pipe, quote(`%<>%`)) ||
identical(pipe, quote(`%$%`))
}
# Determine whether an non-evaluated call is parenthesized
#
# @param a non-evaluated expression
# @retun logical - TRUE if expression is parenthesized, FALSE otherwise.
is_parenthesized <- function(expr)
{
is.call(expr) && identical(expr[[1L]], quote(`(`))
}
# Check whether a pipe is a tee.
#
# @param pipe A (quoted) pipe
# @return logical - TRUE if pipe is a tee, FALSE otherwise.
is_tee <- function(pipe)
{
identical(pipe, quote(`%T>%`))
}
# Check whether a pipe is the dollar pipe.
#
# @param pipe A (quoted) pipe
# @return logical - TRUE if pipe is the dollar pipe, FALSE otherwise.
is_dollar <- function(pipe)
{
identical(pipe, quote(`%$%`))
}
# Check whether a pipe is the compound assignment pipe operator
#
# @param pipe A (quoted) pipe
# @return logical - TRUE if pipe is the compound assignment pipe,
# otherwise FALSE.
is_compound_pipe <- function(pipe)
{
identical(pipe, quote(`%<>%`))
}
# Check whether expression is enclosed in curly braces.
#
# @param expr An expression to be tested.
# @return logical - TRUE if expr is enclosed in `{`, FALSE otherwise.
is_funexpr <- function(expr)
{
is.call(expr) && identical(expr[[1L]], quote(`{`))
}
# Check whether expression has double or triple colons
#
# @param expr An expression to be tested.
# @return logical - TRUE if expr contains `::` or `:::`, FALSE otherwise.
is_colexpr <- function(expr)
{
is.call(expr) &&
(identical(expr[[1L]], quote(`::`)) || identical(expr[[1L]], quote(`:::`)))
}
# Check whether a symbol is the magrittr placeholder.
#
# @param symbol A (quoted) symbol
# @return logical - TRUE if symbol is the magrittr placeholder, FALSE otherwise.
is_placeholder <- function(symbol)
{
identical(symbol, quote(.))
}
# Check whether a package is installed and at least a certain version
is_available <- function(package, version = NULL) {
installed <- nzchar(system.file(package = package))
if (is.null(version)) {
return(installed)
}
installed && isTRUE(utils::packageVersion(package) >= version)
}
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