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valarray class look's same to array class, can you please explain me where would I prefer valarray over array or vice versa?

manlio
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codekiddy
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    See http://stackoverflow.com/questions/1602451/c-valarray-vs-vector – johnsyweb Jan 22 '12 at 23:14
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    It is `valarray`, not `vallaray`. They are not the same thing at all, you probably should not use `valarray` since it is so poorly thought as to render it useless. The difference between `array` and `vector` should suffice. – Alexandre C. Jan 22 '12 at 23:16

3 Answers3

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  • valarray was already in C++03, array is new in C++11
  • valarray is variable length, array is not.
  • valarray is designed for numeric computations and provides plenty of operations including +, -, *, cos, sin, etc... array does not.
  • valarray has an interface to retrieve slices of the array (sub arrays), array does not.
rubenvb
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Yakov Galka
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  • while all the answers are good and each has something more I wasn't know which to accept. so thanks to all of you!. – codekiddy Jan 22 '12 at 23:28
  • Permit me to add a couple of links about `array` and `array` versus `vector` http://en.cppreference.com/w/cpp/container/array and http://stackoverflow.com/questions/15079057/arrays-vs-vectors-introductory-similarities-and-differences – Reb.Cabin Aug 23 '15 at 14:57
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valarray is a dynamic data structure, whose size can change at runtime and which performs dynamic allocation. array is a static data structure whose size is determined at compile time (and it is also an aggregate).

Don't use valarray, though; just use a vector instead.

Kerrek SB
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    @zhermes: hm, maybe [check this question](http://stackoverflow.com/questions/1602451/c-valarray-vs-vector) for some background information. Essentially, standard algorithms and `vector` give you everything you need. – Kerrek SB Jan 23 '12 at 04:18
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The class templates related to std::valarray<T> are intended to support optimizations techniques known as expression templates. I haven't tried to do this but my understanding is that the specification doesn't quite require this and also doesn't really support this sufficiently. In general std::valarray<T> is a fairly specialized class and it isn't really broadly used. Also, I think the template arguments support for std::valarray<T> are a limited set (e.g. the numeric built-in types).

On the other std::array<T, n> is a fixed size array supporting, as far as possible while being fixed size, the normal container interface. Essentially, std::array<T> is a more convenient to use version of T[n].

Dietmar Kühl
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