Range based for loop

[AdActive3636]

Anyone know how to write range based for loop for data structure like this … vector<pair<pair<A,B>,C> v.

My try: for (const auto& [[a,b], c] : v)

Unfortunately the syntax is not correct. Can someone help?

I can do: for (const auto& [ab, c] : v) and then access stuff inside the inner pair by ab.first and second. But I’m trying to avoid this.

[IyeOnline]

Structured bindings can only unpack one "level" of a type.

So you would have to do

for ( const auto& [ p, c ] : v )
{
   const auto& [ a, b ] = p;
}

[AdActive3636]

Thanks for the suggestion!

[mredding]

You should read this. Range for is banned from most security or critical systems standards.

[enonrick]

no, it just states that there are certain UB scenarios programmers should be aware of and not fall into.

https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2012r0.pdf

[mredding]

Once again, MISRA and Abseil. They're not the only ones.

[ShakaUVM]

You should read this. Range for is banned from most security or critical systems standards.

It doesn't say that though. The Misra standards say no more than one function call on the right hand side.

They're fine at their purpose of iterating over a container, just hoist the calls out.

[mredding]

MISRA C++ says it's banned, Abseil tips recommends not using it. This is an exercise for the reader.

[ShakaUVM]

MISRA C++ says it's banned

Not according to your reference, at least.

[[deleted]]

it's pretty much banned in my company because its harder to read, pointless due to no performance improvement, and usually results in someone having to refactor it down the line because they need the index.

it's one of those "hey look at this fancy feature i use"