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delphisetoperatorsdelphi-2007

How to check if a subset is included into a set?

I have two set type variables and I need to check if the first is a subset of the second one.

type
  TMyValue = (mvOne, mvTwo, mvThree);
  TMyValues = set of TMyValue;

...

var
  V1 : TMyValues;
  V2 : TMyValues;
begin
  V1 := [mvOne, mvTwo];
  V2 := [mvOne, mvTwo, mvThree];

  if(V1 in V2)
  then ShowMessage('V1 is a subset of V2')
  else ShowMessage('V2 is not a subset of V2');
end;

The example code gives me the following error on compiling:

[DCC Error] Unit1.pas(36): E2010 Incompatible types: 'TMyValues' and 'TMyValue'

Is there an operator or an "embedded function" to check if values of V1 are all in V2?

Solution

  • Set operator <= allow to check whether V1 is subset of V2 (reference to online help)

    if(V1 <= V2)...

    Note that empty set is subset of any set.

    Operator in should check appearance of single element in set, so it's usage was wrong here.