compare -- compares two elements in a poset

Synopsis

Usage:

r = compare(P, a, b)
Inputs:
- P, an instance of the type Poset,
- a, a thing, an element of the poset
- b, a thing, an element of the poset
Outputs:
- r, a Boolean value, whether $a \leq b$ in $P$

This method determines if two elements are comparable and further if $a$ is less than or equal to $b$ in $P$.

i1 : P = poset {{a,b},{a,c}};

i2 : compare(P, a, b)

o2 = true

i3 : compare(P, c, a)

o3 = false

If two elements are incomparable, then the result is false.

i4 : compare(P, b, c)

o4 = false