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David Wood wrote in his e-mail message of 1995/11/24

GAP seems to have some problems whenever doing an assignment or

arithmetic operation to an element of a list which is represented as a

range with a negative difference.gap> a := [10,8..2]; [ 10, 8 .. 2 ] gap> a[3] := a[3] + 4; 10 gap> a; [ 10, -2, 10,, ]

I'm unable to repeat this problem here. Could you tell us which version

of GAP you are using, and on which machine this happens? Maybe other

GAP users can try this too and write us if this fails for them too

(maybe this is a machine/system/compiler dependent problem).

I suggest that we move this to 'GAP-Trouble@Math.RWTH-Aachen.DE' until

we have sorted it out.

He continued

Is there any way to force GAP to represent a list using the ordinary

list representation, instead of the compact range representation, even

when GAP has realised the list is in fact a range?

Simply adding '0' to the range will do the trick. 'IsRange' can be used

for the other direction (i.e., if you have a list that you know is a

range).

Martin.

-- .- .-. - .. -. .-.. --- ...- . ... .- -. -. .. -.- .- Martin Sch"onert, Martin.Schoenert@Math.RWTH-Aachen.DE, +49 241 804551 Lehrstuhl D f"ur Mathematik, Templergraben 64, RWTH, 52056 Aachen, Germany

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