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Contents
module Rley # This module is used as a namespace
module GFG # This module is used as a namespace
# Abstract class. Represents a vertex in a grammar flow graph
# Responsibilities:
# - To know its outgoing edges
# - To know its label
class Vertex
# The edges linking the successor vertices to this one.
attr_reader :edges
def initialize()
@edges = []
end
# Add an graph edge to this vertex
def add_edge(anEdge)
arrow = check_add_edge(anEdge)
edges << arrow
end
# Returns true iff the vertex corresponds to an dotted item that has
# its dot at the end of a production (i.e. is a reduced item).
def complete?()
return false # Default implementation
end
# Return the symbol before the dot else nil.
def prev_symbol()
return nil # Default implementation
end
# Return the symbol after the dot else nil.
def next_symbol()
return nil # Default implementation
end
protected
# Validation method for adding an outgoing edge to the vertex.
# Vertices will accept an indegree and outdegree of at most one
# unless this method is overridden in subclasses
def check_add_edge(anEdge)
raise StandardError, 'At most one edge accepted' unless edges.empty?
return anEdge
end
end # class
end # module
end # module
# End of file
Version data entries
22 entries across 22 versions & 1 rubygems