CODEWITHSUNDEEP
arraysc++11foreachlambda
tommyk
tommyk

Reputation: 3307

Elegant and efficient way to modify all elements of std::array

I would like to add certain offset to all the data stored in std::array container:

std::array<double, 256> data;
ReadData(data);

// apply data offset
const double OFFSET = 0.123;
data += OFFSET;

It can be done with e.g. std::for_each and lambda.

std::for_each(data.begin(), data.end(), [=OFFSET](auto& n){ n += OFFSET; });

I was wondering if there is a more elegant, less verbose and efficient way to achieve this.

Upvotes: 3

Views: 581

Answers (3)

Ilya Popov
Ilya Popov

Reputation: 4010

If you are not strictly bound to std::array type, you have a choice of other containers that provide overloaded arithmetic operators.

In the standard library there is std::valarray, where you can write:

std::valarray<double> data(256);
ReadData(data);

data += OFFSET;

If you need more operations, like solving systems of linear equations, interpolating, etc, you can use full linear algebra library, like Eigen. Other choices include boost.ublas, Blaze, Armadillo, MTL4 etc.

Upvotes: 3

GingerPlusPlus
GingerPlusPlus

Reputation: 5606

I was wondering if there is a more elegant, less verbose and efficient way to achieve this.

std::transform is in my opinion more elegant that std::for_each, because it's the right tool for the job (std::for_each is more generic). It's more verbose than std::for_each, don't know how about efficiency:

std::transform(data.begin(), data.end(), data.begin(), [=OFFSET](const double n){
    return n + OFFSET;
});

Upvotes: 0

TartanLlama
TartanLlama

Reputation: 65600

Sometimes just writing the loop is clearer than anything else:

for (auto& n : data) n += OFFSET;

Upvotes: 8

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