Sometimes you’re lazy. You know you need to do something, but don’t want to do it yet. You don’t need to do it right now, only at some later point. And maybe later it turns out that you don’t need to do the entire work, just a part of it or nothing at all! So if you’re eager and do it right now, you might do more work than needed.
The same applies to your code. Sometimes you do things even though it is not necessary. You call a function passing it some arguments that were expensive to calculate and then the function don’t need all of them due to some other arguments. Wouldn’t it be great to only calculate the arguments when they are actually needed?
This is called lazy evaluation of function arguments and this blog post presents how it can be done in C++.» read more »