# dropElements -- computes the induced subposet of a poset given a list of elements to remove

## Synopsis

• Usage:
Q = dropElements(P, f)
Q = dropElements(P, L)
Q = P - L
• Inputs:
• P, an instance of the type Poset,
• L, a list, containing elements of $P$ to remove
• f, , which returns true for elements to remove and false otherwise
• Outputs:
• Q, an instance of the type Poset,

## Description

This method computes the induced subposet $Q$ of $P$ with the elements of $L$ removed from the poset.

 i1 : P = chain 5; i2 : dropElements(P, {3}) o2 = Relation Matrix: | 1 1 1 1 | | 0 1 1 1 | | 0 0 1 1 | | 0 0 0 1 | o2 : Poset i3 : P - {4, 5} o3 = Relation Matrix: | 1 1 1 | | 0 1 1 | | 0 0 1 | o3 : Poset

Alternatively, this method computes the induced subposet $Q$ of $P$ with the elements removed which return true when $f$ is applied.

 i4 : P = divisorPoset (2*3*5*7); i5 : Q = dropElements(P, e -> e % 3 == 0) o5 = Q o5 : Poset i6 : Q == divisorPoset(2*5*7) o6 = true