45 lines
1.4 KiB
Elixir
45 lines
1.4 KiB
Elixir
defmodule RDF.Query.BGP do
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@moduledoc """
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A struct for Basic Graph Pattern queries.
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See `RDF.Query` and its functions on how to construct this query struct and
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apply it on `RDF.Graph`s.
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"""
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@enforce_keys [:triple_patterns]
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defstruct [:triple_patterns]
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@type variable :: String.t()
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@type triple_pattern :: {
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subject :: variable | RDF.Term.t(),
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predicate :: variable | RDF.Term.t(),
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object :: variable | RDF.Term.t()
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}
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@type triple_patterns :: list(triple_pattern)
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@type t :: %__MODULE__{triple_patterns: triple_patterns}
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@doc """
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Return a list of all variables in a BGP.
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"""
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@spec variables(any) :: [atom]
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def variables(bgp)
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def variables(%__MODULE__{triple_patterns: triple_patterns}), do: variables(triple_patterns)
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def variables(triple_patterns) when is_list(triple_patterns) do
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triple_patterns
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|> Enum.flat_map(&variables/1)
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|> Enum.uniq()
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end
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def variables({s, p, o}) when is_atom(s) and is_atom(p) and is_atom(o), do: [s, p, o]
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def variables({s, p, _}) when is_atom(s) and is_atom(p), do: [s, p]
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def variables({s, _, o}) when is_atom(s) and is_atom(o), do: [s, o]
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def variables({_, p, o}) when is_atom(p) and is_atom(o), do: [p, o]
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def variables({s, _, _}) when is_atom(s), do: [s]
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def variables({_, p, _}) when is_atom(p), do: [p]
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def variables({_, _, o}) when is_atom(o), do: [o]
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def variables(_), do: []
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end
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