As i needed arrays (for constructing functions for creating large matrices), i
didnt find any suiting objects in GAPs docu, but perhaps its my fault and i
only didnt find it.
List processing only allows for access to already bound elements and only one
indexlevel for enlarging lists. So you cannot freely index list elements
especially
for programming purposes creating and processing lists of arbitrary nesting
levels.
So I wrote a function for the definition of arbitrary arrays of empty lists,
and included it for interested people here. Alas this function has experimental
status yet. May be there are errors or bugs, but in general this would be the
direction to go for this purpose.
If you have knowledge of an equivalent standard function in GAP I would be
grateful to get feedback.
Best regards, Rudolf Zlabinger
Array:=function(bounds)
# creates an array of empty lists of arbitrary nesting levels (dimensions)
# and bounds for each level
# bounds is a list of positive integers determining the length of each dimension
# the length of bounds is the dimension of the array
# at element level the dimension of the array is 1 higher,
# as the last level are also empty lists
local array,IterateArray;
IterateArray:=function(array,bounds)
# iterative call for decreasing levels of array and bounds
local i,dim,boundsrecall;
# i.. index,
# dim the recent level of bounds,
# boundsrecall.. shortened bounds for recalls
dim:=Length(bounds); # the varying length of bounds
for i in [1..bounds[1]] do # 1 recallcascade for one add
Add(array,[]); # enlarging the recent level of array
if dim>1 then # dim=1 is the last level
boundsrecall:=bounds{[2..dim]}; # shorten bounds for next level
IterateArray(array[i],boundsrecall); # recursion for the next lower level
of array
fi; # end of dimension > 1 clause
od; # end of bound loop
return array;
end;
array:=[];
array:=IterateArray(array,bounds); # starting call of add cascade
return array;
end;_______________________________________________
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