Adding parameter with trafo a bit tricky

[mb706]

Suppose a ParamSet contains parameters that have a trafo, and one wants to add a new parameter that also has a trafo. Old ParamHelpers could do this incrementally, by doing

par.set = c(par.set,
  makeParamSet(
    makeNumericParam("scale_pos_weight", lower = -10, upper = 10,
      trafo = function(x) 2^x)))

with paradox this is harder because the $trafo is overwritten, so one must write the $trafo function completely with all transformations.

[jakob-r]

This is totally right. But how often does it occur? Can we prevent the problem of dynamically changing a ParamSet in another way?

In ParamHelpers we spent much time implementing stuff to allow these dynamic changes and realized in the end that we actually don't use it that much. Often it is much easier to do thin in another place.

Btw, I had a paradox ParamSet combine function that did exactly that but it got scraped:

paradox/R/ParamSet.R

Lines 248 to 278 in c7c39fd

	combine = function(param_set) {
	if (self$length == 0) {
	return(param_set$clone())
	} else if (param_set$length == 0) {
	return(self$clone())
	}
	if (length(intersect(self$ids, param_set$ids)) > 0) {
	stop ("Combine failed, because new param_set has at least one Param with the same id as in this ParamSet.")
	}
	new_restriction = self$restriction %??% param_set$restriction
	if (!is.null(self$restriction) && !is.null(param_set$restriction)) {
	new_restriction = substitute((a) && (b), list(a = self$restriction %??% TRUE, b = param_set$restriction %??% TRUE))
	}
	new_trafo = self$trafo %??% param_set$trafo
	if (!is.null(self$trafo) && !is.null(param_set$trafo)) {
	new_trafo = function(x, dict, tags) {
	x = self$trafo(x, dict, tags)
	x = param_set$trafo(x, dict, tags)
	return(x)
	}
	}
	ParamSet$new(
	id = paste0(self$id, "_", param_set$id),
	handle = self$handle$clone(), #FIXME: If the handle is actually used this might not be a good idea, throw error?
	params = c(self$params, param_set$params),
	dictionary = c(as.list(self$dictionary), as.list(param_set$dictionary)),
	tags = union(self$tags, param_set$tags),
	restriction = new_restriction,
	trafo = new_trafo
	)
	},

[berndbischl]

Isn't this nearly the same issue?
#245

[berndbischl]

You can basically achieve exactly what you want Martin trough clean functional composition?