Why Iterators Got It All Wrong — and what we should use instead

C++ iterators are broken by design. Their ambiguity creates subtle bugs with modern ranges. It's time for a safer, more explicit model.

#1about 1 minute

The dual role of C++ iterators as elements and borders

C++ iterators, modeled after pointers, are used ambiguously to represent both specific elements and the borders between them.

#2about 1 minute

Writing cleaner code with C++ ranges

C++20 ranges simplify code by reducing the boilerplate of begin() and end() calls required with traditional iterator pairs.

#3about 4 minutes

Using range adapters for lazy transformations

Range adapters like transform allow for lazy evaluation, separating data projection from the search operation for more modular code.

#4about 2 minutes

How filter adapters create ambiguity for borders

The filter adapter demonstrates a flaw where mapping a border from a filtered range back to the original range is ambiguous.

#5about 5 minutes

The core problem with the reverse adapter

The reverse adapter proves that a single .base() method cannot correctly map both elements and borders back to the original range.

#6about 3 minutes

A formal solution with element and border concepts

The fundamental iterator flaw can be solved by introducing two distinct concepts: 'border' for positions between items and 'element' for the items themselves.

#7about 4 minutes

Improving algorithms with nullable elements and better names

Further improvements include making element types nullable to handle 'not found' cases cleanly and using more descriptive algorithm names like binary_find.

#8about 2 minutes

Conclusion and the think-cell range library

The think-cell C++ range library implements concepts like nullable elements and refined algorithms to address the inherent flaws in standard iterators.

#9about 4 minutes

Q&A on iterator invalidation and border types

The speaker addresses audience questions regarding how the border and element distinction interacts with container iterator invalidation and mathematical open or closed intervals.