Iterator Haiku
summary
Ranges TS shows that adding Concept-driven iterator categories expands five standard categories into seven iterator categories then a Sentinel-focused redesign collapses them back to five by dropping unnecessary equality requirements. It uses Concepts and Sentinels to distinguish weak vs strong iterator requirements, finds a transitivity contradiction with stateful Sentinels, removes the offending cross-type equality, and converts a class of undefined runtime behaviors into compile-time errors while preserving expressiveness.
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chapters (22)
- 0:00Intro
- 0:42OVERVIEW
- 1:58RANGES IN STANDARD C++
- 2:39RANGE SEQUENCE ELEMENTS BETWEEN TWO ITERATORS
- 4:27THE FIVE C++14 ITERATOR CATEGORIES
- 9:24DOMAIN OF A FUNCTION
- 10:20FORWARD DOMAIN OF
- 11:02INPUT DOMAIN OF
- 13:36PALO ALTO TR
- 21:135 HAVE BECOME 7
- 23:38SENTINEL CONCEPT
- 25:04COMMON TYPE
- 29:16CROSS-TYPE EQUALITYCOMPARABLE
- 31:38ALGORITHMS DONT USE == FOR SINGLE-PASS ITERATORS
- 34:01AXIOMATIZATION OF ITERATORS WITH SENTINELS
- 35:43STATEFUL SENTINELS AND "ALWAYS EQUAL"
- 39:38START OVER WITH ALGORITHM REQUIREMENTS
- 41:09WEAKLYEQUALITYCOMPARABLE
- 42:12WEAK RANGES ARE POSSIBLE
- 42:58STATEFUL SENTINELS WORK
- 45:16MOST IMPORTANTLY
- 46:54TAKEAWAY CONCEPT LIBRARY DESIGN
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