add note of cppcon

Author: Sophomore42

_code/CppCon/2021/back_to_basics_lambdas.md

@@ -1,5 +1,5 @@
 ---
-title: Back to Basics: Lambdas by Nicolai Josuttis
+title: "Back to Basics: Lambdas by Nicolai Josuttis"
 date: 2024-11-21
 url: https://www.bilibili.com/video/BV1ha411k7pa?p=138
 ---
@@ -35,3 +35,5 @@ the type of lambdas need to be auto.
 the auto in lambda make the `operator()` a function template. But lambda self is still a function object which can be pass to a function. But a function template it self can't.
 
 lambda capture with value is stateless, lambda capture with reference and mutable is stateful.
+
+Note: the value and the reference of the lambda is different.

_code/CppCon/2023/back_to_basics_iterators.md

@@ -0,0 +1,79 @@
+---
+title: "Back To Basics: Iterators by Nicolai Josuttis"
+date: 2024-11-22
+url: https://www.bilibili.com/video/BV1BC4y1R7iL?p=30
+---
+
+other talk from this reporter: [markdown](../2021/back_to_basics_lambdas.md)
+
+Loop over array.
+
+- with index
+- with pointer
+
+Iterators: generalization of pointers that iterate
+
+`begin`and`end`
+
+note: end is not the element. It's a half one range. It's no need to deal with empty collections.
+
+## Why Iterators?
+
+Iterators can deal with multi data structure.
+
+Used by the range-based for loop.
+
+`const_iterator` means the element the iterator refers to is const. This is also equals to `cbegin`and`cend`
+
+iterators have different categories.
+
+- random access iterator: can jump to and compare with other position
+- bidirectional iterator: can iterate forward and backward
+- forward iterator: can iterate forward only
+- input iterator: can read elements only once
+- contiguous range/iterator(since c++ 20):support for std::ranges::data()
+
+note: deque is a array of a array so it's a random access iterator but not a contiguous iterator
+
+## Iterator and Algorithms
+
+iterators as glue interface.
+
+ref:std::max_element
+
+```c++
+if(result != foo.end())
+```
+
+handel the result.
+
+ref:std::accumulate
+
+Algorithms are generic
+
+note:std::set sort the element automatic
+
+pure abstraction: everything that behaves like a iterator is a iterator.
+
+Separate data and function.
+
+## Pitfalls of Iterators
+
+append element maybe will change the location of the container.
+
+std::transform()with 4 arguments. Destination need to be a output iterators, and there must be elements to overwrite.
+
+- Need to resize the destination array.
+- using `std::back_inserter`
+
+std::remove remove the elements but doesn't resize the container, it remain the value. Iterator can't remove the elements.
+
+Removing algorithms do note remove, instead they replace removed elements and return the new end.
+
+ref:std::ranges::subrange and std::views::filter
+
+view cache the begin
+
+modification of the element a filter_view::iterator denotes is permitted, but results in undefined behavior if the resulting value does not satisfy the filter predicate.
+
+