Structured bindings in C++17, 8 years later

by Bartlomiej Filipek

An excellent demonstration of structured bindings is an iteration through a map object.

If you have a std::map of elements, you might know that internally, they are stored as pairs of <const Key, ValueType>.

Now, when you iterate through elements, you can do:

for (const auto& elem : myMap) { ... } 

You need to write elem.first and elem.second to refer to the key and the value.

std::map<KeyType, ValueType> myMap = getMap(); 
// C++14: 
for (const auto& elem : myMap) {  
     // elem.first - is the key  
     // elem.second - is the value 
}

You should use QPainterPath they said...

by Jens Weller

This post is about what I learned while playing around with QPainterPath for this years t-shirt at Meeting C++ 2025 sponsored by Hudson River Trading.

One of the issues from last years t-shirt was when using drawText from QPainter, one does not really *draw* text in an svg exported. Instead you'll get the text and the font kinda embedded in an svg. What good is that in a vector graphic? This was a bit of a surprise when I ran into issues with this last year during printing. While this could be solved with the printing company picking a different font, it would have been also solved by using QPainterPath. At least this was the feedback from some of the Qt experts present onsite or online...

Final call for sponsors for Meeting C++ 2025

by Jens Weller

With Meeting C++ 2025 just being 5 weeks away, I share a call for sponsors with you.

Maybe your employer is interested in being present as a sponsor at this years Meeting C++ conference? Have you thought about the possibilty that you could have your employer sponsor Meeting C++ 2025?

How to Look up Values in a Map

by Sandor Dargo

Let’s explore the different options — along with their pros and cons.

operator[]

Using operator[] is the old-fashioned way to access elements of a map. It takes a key and returns a reference to the corresponding value. The complexity is log(n) for std::map and average constant time (with worst-case linear) for std::unordered_map.

However, there’s a big caveat.

What if the key is not present in the map?

Unlike a vector — where accessing an invalid index with operator[] leads to undefined behavior — a map will instead insert a new entry with the given key and a default-constructed value. This side effect makes operator[] unsafe for lookups where insertion is not desired.