ruby,recursion , How to flatten a structure of embedded Set and Hash

## Question:

Tag: ruby,recursion

I would like to convert an embedding structure into a flat one.

• An embedding structure is a set of 0 or more objects, such as: a string or a hash having some string as key and some other embedding structure as value.
• A flat structure is a set of arrays or strings.

Here some examples:

t(
Set[]
) # => Set[]

t(
Set[ 'foo' ]
) # => Set[ ['foo'] ]

t(
Set[ 'foo0',
'foo1',
'foo2' ]
) # => Set[ ['foo0'], ['foo1'], ['foo2'] ]

t(
Set[ 'foo' => Set[ 'bar' ] ]
) # => Set[ ['foo', 'bar'] ]

t(
Set[ 'foo' => Set[ 'bar0', 'bar1', 'bar2' ] ]
) # => Set[ ['foo', 'bar0'],
#         ['foo', 'bar1'],
#         ['foo', 'bar2'] ]

t(
Set[ {'foo' => Set[ 'bar0', 'bar1', 'bar2' ]},
{'FOO' => Set[ 'BAR0', 'BAR1', 'BAR2' ]} ]
) # => Set[ ['foo', 'bar0'],
#         ['foo', 'bar1'],
#         ['foo', 'bar2'],
#         ['FOO', 'BAR0'],
#         ['FOO', 'BAR1'],
#         ['FOO', 'BAR2'] ]

t(
Set[ {'foo' => Set[ {'FOO' => Set[ 'BAR' ]} ]} ]
) # => Set[ ['foo', 'FOO', 'BAR'] ]

t(
Set[ {'foo' => Set[ {'FOO' => Set[ 'BAR' ]} ]},
'baz' ]
) # => Set[ ['foo', 'FOO', 'BAR'],
#         'baz' ]

t(
Set[ {'foo' => Set[ {'FOO' => Set[ 'BAR0', 'BAR1' ]} ]},
'baz' ]
) # => Set[ ['foo', 'FOO', 'BAR0'],
#         ['foo', 'FOO', 'BAR1'],
#         ['baz'] ]

t(
Set[ {'foo' => Set[ {'FOO' => Set[ 'BAR0', {'BAR1' => Set[ {'abc' => Set[ 'def' ]} ]} ]} ]},
'baz' ]
) # => Set[ ['foo', 'FOO', 'BAR0'],
#         ['foo', 'FOO', 'BAR1', 'abc', 'def'],
#         ['baz'] ]


I think we should use resistivity to convert the given structure. But I have no idea for an implementation. Please feel free to any example of t function.

Edit:

In other words, I would like to develop the embedding structure into a flatten structure.

We can see the embedding structure such as an expression with factors. And if we multiply them, the flatten structure is returned.

require 'set'
def t_h(inp, prefix = [])
if (inp.is_a?(Hash))
result = []
inp.each do |k,v|
pprefix = prefix.dup
result << t_h(v, pprefix << k)
end
return result.flatten(1)
elsif (inp.is_a?(Set))
result = []
inp.each do |el|
result << t_h(el, prefix)
end
return result.flatten(1)
else
pprefix = prefix.dup
return [ pprefix << inp ]
end
end

def t(inp)
Set.new(t_h(inp))
end

# examples
t(Set[ 'foo' => Set[ 'bar' ] ])
t(Set[ 'foo' => Set[ 'bar0', 'bar1', 'bar2' ] ])
t(
Set[ {'foo' => Set[ 'bar0', 'bar1', 'bar2' ]},
{'FOO' => Set[ 'BAR0', 'BAR1', 'BAR2' ]} ]
)


Code is far from optimal, but you get the idea.

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