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Hi,

I'm having a problem in GAP when I attempt to assign entries

to lists. Apparently my problem is due to the way GAP makes

assignments. I've read the section on Lists in the GAP manual, but I

am still struggling to understand this. (I apologize in advance for

asking a question apparently covered in the manual!)

Explicitly -- I don't understand why the following loops give

different answers. The first example creates the array

[[1,2,3,4][5,6,7,8]] while the second does not.

Why?

(I am running GAP 4.1 on a Macintosh G3 laptop -- if that matters.)

---- GAP program ------------ #Filling in an array -- example 1 mat := [[0,0,0,0], [0,0,0,0]]; Print( mat, "\n" ); entry := 0; for i1 in [1..2] do for i2 in [1..4] do entry := entry + 1; mat[i1][i2] := entry; mat2 := mat; Print( mat, "\n" ); od; od; Print("\n"); #Filling in an array -- example 2 zero_1 := ListWithIdenticalEntries( 4, 0 ); mat := ListWithIdenticalEntries( 2, zero_1 ); Print( mat, "\n" ); entry := 0; for i1 in [1..2] do for i2 in [1..4] do entry := entry + 1; mat[i1][i2] := entry; mat2 := mat; Print( mat, "\n" ); od; od; ------

The real problem I am working on attempts to create

3-dimensional t x r x c arrays for various abelian groups of rank 3,

so the programming is more complicated than this simple example.

However, I think an explanation of this small example would be very

helpful.

Thanks, Ken -- Ken W. Smith, Professor of Mathematics, Central Michigan University Phone: 517-774-6521; Fax: 517-774-2414; home phone: 772-5042.

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