Implement BoundedVec with bound on both end

[sudipghimire533]

Is there an existing issue?

• [X] I have searched the existing issues

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• [X] This is not a support question.

Motivation

BoundedVec will not only bound its size in maximum limit but there shall also be minimum limit. This is useful in many case where pallet is expecting a vector within certain bounds eg: Some Name shall be greater than 3 element long but less than 500 and so on

Request

Extend BoundedVec implementation in frame_support to include another type Paramater LowerBound and all the operation in BoundedVec gurantee this bound ( and also the current upperbound ).

If required, default LowerBound can be 0 so it does not change the behavior in places where lower bound is not required

Solution

Explain Above

( I can also take the responsibility to implement and raise the PR, but first i need confirmation if everyone else thinks this is worth having )

Are you willing to help with this request?

Yes!

[sudipghimire533]

If changing the implementation of Current BoundedVec is problematic we can also create new struct DoubleBoundedVec to wrap BoundedVec and inner limit

[xlc]

You should implement DoubleBoundedVec (I don't like this name but also can't think of a better one) and then implement BoundedVec on top of it. This way we can minimize the breaking change (no breaking change for existing BondedVec user) and code duplications.