darkkindness

  ┌────────┬────────────────────┐
  │myreduce│┌─────┬────────────┐│
  │        ││mymap│┌────────┬─┐││
  │        ││     ││myfilter│x│││
  │        ││     │└────────┴─┘││
  │        │└─────┴────────────┘│
  └────────┴────────────────────┘

  ┌────────┬────────────┐
  │myreduce│┌────────┬─┐│
  │        ││mymap   │x││
  │        ││        │ ││
  │        ││myfilter│ ││
  │        │└────────┴─┘│
  └────────┴────────────┘

  ┌────────┬─────┬────────┬─┐
  │myreduce│mymap│myfilter│x│
  └────────┴─────┴────────┴─┘

  (myreduce ∘ mymap ∘ myfilter)(x)

  x | myfilter | mymap | myreduce

  myreduce mymap myfilter x

    #ifdef NDEBUG
    #define assert(condition) ((void)0)
    #else
    #define assert(condition) /*implementation defined*/
    #endif

    ...
    assert(("There are five lights", 2 + 2 == 5));
    ...

    test: test.cc:10: int main(): Assertion `((void)"There are five lights", 2+2==5)' failed.