c++ - What is a concise syntax for accessing the other element of two element collection? -


i have 2-element collection {a, b} , complex expression ex(_, _) involving both elements in non-commutative way. result of computation i'm looking equivalent to:

ex(a, b); ex(b, a);

but instead of repeating whole expression twice (defining function computing ex not acceptable), use loop this:

for (auto i: {a, b})   ex(i, <other element>);

what short way of writing such loop?

edit

since number of readers found question unclear, please have @ 2 answers below, present solutions looking for. ex(a, b) shorthand long chunk of code using a , b in order. reasons why don't want define function ex stylistic , beyond scope of question.

if elements indexed 0 , 1 (such in vector v) use exclusive or ^ select alternative index:

for(auto i: {0, 1})     ex(v[i], v[i ^ 1]);

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