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isSource -- determines if a vertex of a digraph is a source or not

Usage:

r = isSource (D, v)
Inputs:
- D, a digraph,
- v, a thing, the vertex being texted
Outputs:
- r, a Boolean value, whether the vertex v is a source or not

Description

A vertex v of a Digraph D is a source if v has no parents

i1 : D = digraph({a,b,c,d,e},{{a,b},{b,c},{b,d},{e,b}});

i2 : isSource (D,c)

o2 = false

i3 : isSource (D,e)

o3 = true

See also

sources -- returns the sources of a digraph

Ways to use isSource:

isSource(Digraph,Thing)

For the programmer

The object isSource is a method function.

The source of this document is in Graphs.m2:4674:0.