Module expr 

Expression algebra for defining quorum systems.

An Expr describes which sets of nodes form a quorum:

• Node: a single node
• Or (a + b): any one child is a quorum
• And (a * b): every child is needed
• Choose (choose): any k of the children

Or, And, and Choose are always non-empty and Choose always has 1 <= k <= children.len(). Their fields are private so those invariants cannot be broken after construction.

Structs

And

AND combinator: all children must be satisfied.

Choose

CHOOSE combinator: at least k children must be satisfied.

Node

A node in a quorum system.

Or

OR combinator: at least one child must be satisfied.

Enums

Expr

An expression describing which sets of nodes form a quorum.

Traits

Element

Trait for types that can be used as node identifiers in quorum expressions.

Functions

choose

Create a choose expression. Returns Or when k == 1, And when k == n, and Choose otherwise.

majority

Create a majority quorum expression. Requires floor(n/2) + 1 children to be satisfied.