Indexing list of lists
David C. Fox
davidcfox at post.harvard.edu
Thu Sep 18 20:25:19 CEST 2003
Hilde Roth wrote:
>>Like it or not, there are no "different dimensions", just lists of lists
> You are being too litteral. A list of list is like a 2D array from an
> indexing point of view, a list of lists of lists like a 3D array etc.
> E.g., (((1,10),(2,20),(3,30)),((-1,'A'),(-2,'B'),(-3,'C'))) is a
> 2 x 3 x 2 rectangular data structure and has 3 dimensions. Hence,
> e.g., l[0;2;1] ~ l = 30
Only if all the sublists are of the same length, which is guaranteed for
a multi-dimensional array, but not for a list of lists.
What do you expect a[;1] to return if a = [, [1, 2, 3], , 5]?
That's why Numeric has a specific type for multi-dimensional arrays.
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