By Adrien Hamelin | Jun 24, 2019 01:27 PM | Tags: community
The series continue.
C++ Core Guidelines: Rules for Strings
by Rainer Grimm
From the article:
The C++ core guidelines use the term string as a sequence of characters. Consequently, the guidelines are about C-strings, C++-strings, the C++17 std::string_view's, and std::byte's...
By Adrien Hamelin | Jun 24, 2019 01:19 PM | Tags: intermediate
Simple and efficient.
A simple workaround for the fact that std::equal takes its predicate by value
by Raymond Chen
From the article:
The versions of the std::equal function that takes a binary predicate accepts the predicate by value, which means that if you are using a functor, it will be copied, which may be unnecessary or unwanted.
In my case, the functor had a lot of state, and I didn’t want to copy it....
By rodburns | Jun 14, 2019 12:03 PM | Tags: None
This blog post offers a generic description of using lambdas in C++ and how it's possible to use them with SYCL, an open standard interface for programming heterogeneous hardware using C++.
Generic Interfaces with Generic Lambdas using C++ for SYCL
by Georgi Mirazchiyski
From the article:
C++ Lambdas, first introduced in C++11, are an important part of the way that the SYCL standard is defined and implemented. SYCL is required to handle different types and pass around functions so lambdas are a good fit allowing anonymous function objects to be passed to SYCL kernels. We talk about how we use lambdas in our guides and documentation, but never about how lambdas work or even how to use them in SYCL, so in this blog post we will examine how they can be used in SYCL.
By Adrien Hamelin | Jun 11, 2019 01:45 PM | Tags: intermediate community
The series continue.
C++ Core Guidelines: Avoid Bounds Errors
by Rainer Grimm
From the article:
When you access an element outside a container of the STL, the result is not so promising. You effect may be an error or undefined behaviour. Undefined behaviour means all bets are open...
By Adrien Hamelin | Jun 10, 2019 12:22 PM | Tags: intermediate community
Quick A: read the SO FAQ.
Recently on SO:
What are the basic rules and idioms for operator overloading?
- The General Syntax of operator overloading in C++
- The Three Basic Rules of Operator Overloading in C++
- The Decision between Member and Non-member
- Common operators to overload
- Overloading new and delete
...
By Marco Arena | Jun 5, 2019 06:43 AM | Tags: c++20 c++17 advanced
A new interpretation of a classical problem:
Kadane in next-gen C++
by Marco Arena
From the article:
We, programmers, get better results while thinking in patterns. We decompose complex problems in combinations of simpler patterns. However, many problems cannot be solved with known patterns. Here is where creativity kicks in...
By Adrien Hamelin | Jun 4, 2019 11:04 AM | Tags: intermediate c++14
Quick A: mostly for exception safety.
Recently on SO:
Differences between std::make_unique and std::unique_ptr with new
The motivation behind make_unique is primarily two-fold:
make_unique is safe for creating temporaries, whereas with explicit use of new you have to remember the rule about not using unnamed temporaries.
foo(make_unique<T>(), make_unique<U>()); // exception safe foo(unique_ptr<T>(new T()), unique_ptr<U>(new U())); // unsafe*The addition of make_unique finally means we can tell people to 'never' use new rather than the previous rule to "'never' use new except when you make a unique_ptr".
There's also a third reason:
make_unique does not require redundant type usage. unique_ptr<T>(new T()) -> make_unique<T>()None of the reasons involve improving runtime efficiency the way using make_shared does (due to avoiding a second allocation, at the cost of potentially higher peak memory usage).
By Adrien Hamelin | Jun 4, 2019 11:01 AM | Tags: intermediate
Quick A: See below
Recently on SO:
With arrays, why is it the case that a[5] == 5[a]?
The C standard defines the [] operator as follows:
a[b] == *(a + b)Therefore a[5] will evaluate to:
*(a + 5)and 5[a] will evaluate to:
*(5 + a)a is a pointer to the first element of the array. a[5] is the value that's 5 elements further from a, which is the same as *(a + 5), and from elementary school math we know those are equal (addition is commutative).
By Adrien Hamelin | Jun 3, 2019 11:55 AM | Tags: performance
Quick A: performance.
Recently on SO:
Why does moving std::optional not reset state?
In a word: Performance.
One of the chief motivating reasons for move semantics to exist in the first place is performance. So the special operations move construction and move assignment should be as fast as possible for all types...
By Adrien Hamelin | Jun 3, 2019 11:47 AM | Tags: stl intermediate
What do you think?
The Difference Between std::copy_backward and std::copy with Reverse Iterators
by Jonathan Boccara
From the article:
A couple of months ago, I made a talk at the ACCU conference about learning every algorithm there is in the STL. Amongst them, we covered std::copy_backward, that makes a copy of a source range to a destination range, starting from its end and working its way back to the beginning.
In the questions session at the end of the talk, attendant Oscar Forner rose an interesting point: is there any difference between performing a std::copy_backward versus performing a simple std::copy on the reverse iterators from the source collection?