1 files changed, 42 insertions, 0 deletions
diff --git a/src/relation.erl b/src/relation.erl
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+++ b/src/relation.erl
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+-module(relation).
+-export([new_attribute/2, new_tuple/1, new_relation/1]).
+
+%% Attribute: A pair of (Name, Value), eg. ("Name", "Augusto")
+%% Tuple: A set of attributes, eg. (("Name", "Augusto"), ("Age", 20), ("Surname", "Rengel"))
+%% Relation: A set of tuples organized through some selector
+%% Example Relation: f(x: Nat) = x + 1
+%% |{(0, 1), (1, 2), (2, 3), ...}| = |N|
+%% RelationCustomer = [(Username, Text), (Password, Text)]
+%% RelationProduct = [(Name, Text), (Price, Real)]
+%% RelationOrder = [(OrderId, Natural), ((Username, Text), 
+%%                                       (Password, Text), RelationCustomer), ((Name, Text), 
+%%                                                                             (Price, Real), RelationProduct)]
+
+new_attribute(Name, Value) ->
+    #{name => Name, value => Value}.
+
+new_tuple(Attributes) when is_list(Attributes) ->
+    Fun = fun (#{name := Name, value := Value}, Acc) ->
+		  maps:put(Name, Value, Acc)
+	  end,
+    lists:foldl(Fun, #{}, Attributes).
+
+new_relation(Tuples) when is_list(Tuples) ->
+    sets:from_list(Tuples, [{version, 2}]).
+
+%% SoapName1 = relation:new_attribute(name, "ABC").
+%% SoapPrice1 = relation:new_attribute(price, 1.0).
+%% SoapName2 = relation:new_attribute(name, "XYZ").
+%% SoapPrice2 = relation:new_attribute(price, 1.25).
+%% BazookaName = relation:new_attribute(name, "Bazzum").
+%% BazookaPrice = relation:new_attribute(price, 413.0).
+%% SwordName = relation:new_attribute(name, "Sword").
+%% SwordPrice = relation:new_attribute(price, 100.0).
+%% relation:new_relation([relation:new_tuple([SoapName, SoapPrice]), relation:new_tuple([BazookaName, BazookaPrice]), relation:new_tuple([SwordName, SwordPrice])]).
+
+%% Jules = relation:new_attribute(customer_name, "Jules").
+%% Emily = relation:new_attribute(customer_name, "Emily").
+%% Customers = relation:new_relation([relation:new_tuple([Jules]),
+%% 				   relation:new_tuple([Emily])]).
+
+%% operations:project(operations:select(operations:cartesian_product(relation:new_relation([relation:new_tuple([SoapName1, SoapPrice1]), relation:new_tuple([SoapName2, SoapPrice2]), relation:new_tuple([BazookaName, BazookaPrice]), relation:new_tuple([SwordName, SwordPrice])]), Customers), fun (Tuple) -> maps:get(price, Tuple) =< 1.0 end), [name, customer_name]).