dagLinkParentToChild

dagLinkParentToChild(
w_parent
w_child 
)
=> w_arc / nil

Creates a dagArc that links the parent node to the child node. It returns the arc it creates. If an error occurs, it returns nil.

The automatic placement algorithm places the children of a parent node in the order in which they were added with this function.

w_parent	Specifies the parent node, head of the arc to be created.
w_child	Specifies the child node, tail of the arc to be created.

w_arc	The new arc.
`nil`	There was an error.