"%||%" <- function(x, y) if (is.null(x)) y else x

is_windows <- function() {

identical(.Platform$OS.type, "windows")

}

is_unix <- function() {

identical(.Platform$OS.type, "unix")

}

is_osx <- function() {

Sys.info()["sysname"] == "Darwin"

}

is_linux <- function() {

identical(tolower(Sys.info()[["sysname"]]), "linux")

}

is_ubuntu <- function() {

# check /etc/lsb-release

if (is_unix() && file.exists("/etc/lsb-release")) {

lsbRelease <- readLines("/etc/lsb-release")

any(grepl("Ubuntu", lsbRelease))

} else {

FALSE

}

}

dir_exists <- function(x) {

utils::file_test('-d', x)

}

ensure_loaded <- function() {

invisible(tf$`__version__`)

}

aliased <- function(path) {

sub(Sys.getenv("HOME"), "~", path)

}

call_hook <- function(name, ...) {

hooks <- getHook(name)

if (!is.list(hooks))

hooks <- list(hooks)

response <- FALSE

lapply(hooks, function(hook) {

if (isTRUE(hook(...)))

response <<- TRUE

})

response

}