31.1 IsRange

IsRange( obj )

IsRange returns true if obj, which may be an object of any type, is a range and false otherwise. A range is a list without holes such that the elements are integers with a constant increment. Will cause an error if obj is an unassigned variable.

    gap> IsRange( [1,2,3] );
    true    # this list is a range
    gap> IsRange( [7,5,3,1] );
    true    # this list is a range
    gap> IsRange( [1,2,4,5] );
    false    # this list is a set and a vector, but not a range
    gap> IsRange( [1,,3,,5,,7] );
    false    # this list contains holes
    gap> IsRange( 1 );
    false    # is not even a list
    gap> IsRange( [] );
    true    # the empty list is a range by definition
    gap> IsRange( [1] );
    true    # singleton lists are a range by definition too 

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