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combinat

  

subsets

  

iterate over the power set of a set or list

 

Calling Sequence

Parameters

Description

Examples

Calling Sequence

subsets(L)

Parameters

L

-

set or list of elements

Description

• 

The function subsets is an iterator for generating the power set of a set one set at a time.  It returns a table with two entries:  finished and nextvalue.

• 

The finished entry will be either true or false, depending on whether the end of the set has been reached. It is initially set to false.

• 

The nextvalue entry is a procedure that traverses the power set. The result of a call to nextvalue will be the next set in the power set. When the entire set has been traversed, nextvalue will set the value of finished to true.

• 

If the input L is a set, the subsets are returned as sets.  If the input is a list, the subsets are returned as lists.  Otherwise the only difference is in the order in which the subsets are generated.

• 

The command with(combinat,subsets) allows the use of the abbreviated form of this command.

Examples

withcombinat:

Ssubsets1,2:

whilenotSfinisheddoSnextvalueenddo

1

2

1,2

(1)

See Also

combinat

combinat[choose]

combinat[powerset]