I like vectors a lot. They're nifty and fast. But I know this thing called a valarray exists. Why would I use a valarray instead of a vector? I know valarrays have some syntactic sugar, but other than that, when are they useful?
9 Answers
With std::valarray you can use the standard mathematical notation like v1 = a*v2 + v3 out of the box. This is not possible with vectors unless you define your own operators.
std::valarray is intended for heavy numeric tasks, such as Computational Fluid Dynamics or Computational Structure Dynamics, in which you have arrays with millions, sometimes tens of millions of items, and you iterate over them in a loop with also millions of timesteps. Maybe today std::vector has a comparable performance but, some 15 years ago, valarray was almost mandatory if you wanted to write an efficient numeric solver.
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