eval_domain.R

combiner = function(x, y = x) {
  out = vector("list"); n = 1
  for (i in x) {
    for (j in y) {
      # if (i %in% j) {
      #   next
      # }
      
      out[[n]] = c(i, j)
      n = n + 1
    }
  }
  return(out)
}

wrapper = function(x = list(c(0, 255), c(0, 255)), n = length(x)) {
  for (h in (n - 1):1) {
    out = if (h == n - 1) {
      combiner(x[[h]], x[[h + 1]])
    } else {
      combiner(x[[h]], out)
    }
  }
  return(out)
}

combineArrs = function(x, y) {
  out = vector("list", length(x))
  for (i in 1:length(x)) {
    out[[i]] = c(x[i], y[i])
  }
  return(out)
}

a = 1:3
b = 10:12

wrapper(combineArrs(a, b))
[[1]]
[1] 1 2 3

[[2]]
[1]  1  2 12

[[3]]
[1]  1 11  3

[[4]]
[1]  1 11 12

[[5]]
[1] 10  2  3

[[6]]
[1] 10  2 12

[[7]]
[1] 10 11  3

[[8]]
[1] 10 11 12


## Thanks to Flo Detsch!!

To get rid of eval and include all Math functions:

var x = -2
undefined
var arith = "abs(x)"
undefined
function evalDomain(a) {
    return Function( 'with(Math) return ' + a)();
}
undefined
evalDomain(arith)
2