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make_closure <- function(fun, ...) {
data <- list(...)
mapply(assign, names(data), data, MoreArgs = list(pos = environment()))
environment(fun) <- environment()
fun
}
has_glpk <- make_closure(glpk = NULL, function() {
if (is.null(glpk)) {
glpk <<- tryCatch(
{
cluster_optimal(make_ring(10))
TRUE
},
error = function(e) FALSE
)
}
glpk
})
has_graphml <- make_closure(graphml = NULL, function() {
if (is.null(graphml)) {
graphml <<- tryCatch(
{
read_graph(
rawConnection(charToRaw("<graphml><graph></graph></graphml>")),
format = "graphml"
)
TRUE
},
error = function(e) FALSE
)
}
graphml
})
|
