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Synopsis Select a field (column) from a relation value.
Syntax Exp . Name
Types
Exp Exp . Name
rel[T1 L1, T2 L2, ... ] set[Ti]
Description Exp should evaluate to a relation that has an i-th field label Li that is identical to Name. Return a set with all values of that field. Name stands for itself and is not evaluated.
Examples 
rascal>rel[str street, int nm] R = {<"abc", 1>, <"abc", 2>, <"def", 4>, <"def", 5>};
rel[str street,int nm]: {
  <"def",4>,
  <"def",5>,
  <"abc",2>,
  <"abc",1>
}
rascal>R.street;
set[str]: {"abc","def"}

Questions
Question [1].
Given 
rel[str animal, int nlegs] legs = {<"bird", 2>, <"dog", 4>, <"human", 2>, <"snake", 0>, <"spider", 8>, <"millepede", 1000>, <"crab", 8>, <"cat", 4>};

legs.animal ==

Question [2].
Given 
rel[str animal, int nlegs] legs = {<"bird", 2>, <"dog", 4>, <"human", 2>, <"snake", 0>, <"spider", 8>, <"millepede", 1000>, <"crab", 8>, <"cat", 4>};

legs.nlegs ==



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