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ListRelation FieldSelection

rascal-0.40.17

Synopsis​

Select a field (column) from a list relation value.

Syntax​

Exp . Name

Types​

ExpExp . Name

| | lrel[T₁ L₁, T₂ L₂, ... ] | list[Tᵢ] |

Description​

Exp should evaluate to a list relation that has an i-th field label Lᵢ that is identical to Name. Return a list with all values of that field. Name stands for itself and is not evaluated.

Examples​

rascal>lrel[str street, int nm] R = [<"abc", 1>, <"abc", 2>, <"def", 4>, <"def", 5>];
lrel[str street,int nm]: [
  <"abc",1>,
  <"abc",2>,
  <"def",4>,
  <"def",5>
]
rascal>R.street;
list[str]: ["abc","abc","def","def"]