# Poset _ List -- returns elements of the ground set

## Synopsis

• Operator: _
• Usage:
V = P_L
• Inputs:
• P, an instance of the type Poset,
• L, a list, indices in the ground set
• Outputs:
• V, a list, the vertices indexed by $L$ in the ground set

## Description

This method allows easy access to the vertices of the poset.

 i1 : P = booleanLattice 3; i2 : P_{2,4,5} o2 = {010, 100, 101} o2 : List