3.5 Set operations with named query results

• named queries can be copied, especially before destructive modification (see below)

  > B = A;
> C = Last;

• compute subset of named query result by constraint on one of the anchor points

  > PP = [pos="IN"] [pos="JJ"]+ [pos="NNS?"];
> group PP matchend lemma by match word;

  > PP1 = subset PP where match: "in";
> PP2 = subset PP1 where matchend: [lemma = "time"];
  $\to$ PP2 contains instances of in ... time(s)

• set operations on named query results

  > A = intersection B C;	$A = B \cap C$
  > A = union B C;	$A = B \cup C$
  > A = difference B C;	$A = B \setminus C$

  intersection (or inter) yields matches common to B and C; union (or join) matches from either B or C; difference (or diff) matches from B that are not in C

• cut query result to first $n$ matches

  > cut A 50; (first 50 matches)

  or select a range of matches (as with the restricted cat command)

  > cut A 50 99; (51 $^{\text{st}}$ – 100 $^{\text{th}}$ match)

  NB: cut A 50; is exactly the same as cut A 0 49;

• The modifier cut $n$ can als be appended to a query:

  > "time" cut 50;

  The main purpose of this usage is to reduce memory consumption and processing time in Web interfaces and similar applications by stopping query execution early if a sufficient number of matches has been found. For internal reasons, this optimization cannot be applied to queries with alignment constraints (see Sec. 5.2); but the cut modifier still guarantees that only the first $n$ matches will be returned.