HowTo get the previous element from std::deque?

Question

Hi there.

For example I have an array with about 10 elements in it.

std::deque<int> d;
front_inserter(d) = 100;
front_inserter(d) = 200;
front_inserter(d) = 300;
...
front_inserter(d) = 900;
front_inserter(d) = 1000;

Question: how to find 900 element, without using [] access? If the size of the massive will be changes, for example to 123, how to find 122 element?

PS: I don't want to use [] because this method does not perform d[-1] check...

Thanks.

Answer 1

use deque::at.

d.at(121)

Answer 2

If you mean a runtime check throwing in case of out of bound access you can use ::at(pos). If you mean d[-1] being the last element, d[-2] the second-last and so on (a-la Python) then you've to code your own (possibly template) function for that.