Assigning value to an array element inside a function

Question

A simple function

auto f = [] (const array <GLfloat, 4> a, array <GLfloat, 4> b) {b [2] = a [2] + 5;};

does not work as expected - array b remains unchanged.

Barry · Accepted Answer · 2015-09-04 23:35:33Z

4

Because you're passing by value and simply modifying the copied array, which has nothing to do with the outer b. You have to pass by reference:

auto f = [](const array<GLfloat, 4>& a, array<GLfloat, 4>& b) {b[2] = a[2] + 5;};
                                                       ^^^^

You should pass a by reference-to-const as well, to avoid the unnecessary copy.

answered Sep 4, 2015 at 23:35

Barry

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