Fuzion • Idioms • Idiom # 100: Sort by a comparator

Idiom # 100: Sort by a comparator

Code

Runnable Example

Sort using implicit order of items:

Sort using comparator c wrapped into c_order:

ex100 is

  items := [ "siebenundvierzig";
             "elf";
             "null";
             "acht";
             "fünfzehn" ]

  # define order using byte_count
  c(a, b String) => a.byte_count <= b.byte_count

  # define our own orderable feature based on `c` from above
  c_order(val) : property.orderable is

    # compare val to b.val
    cmp(b c_order.this)
    =>
      c val b.val

    public redef type.lteq(a, b c_order.this) bool
    =>
      # compare a and b.
      #
      # Note that `c` is not visible from this type feature `lteq`, so
      # we cannot do `c a b` unless `c` is moved to universe or we use
      # `ex100.c` (which we cannot do here since this would re-run the
      # example recursively).
      a.cmp b

  # and now sort by c_order
  say (items.sort_by c_order)

What are effects?

Sort using a mapping to byte_count.

last changed: 2026-07-23

next: NYI: Idiom # 101: Load from HTTP GET request into a string