Before we implement what we said we would regarding rank-0 arrays in numarray, there became apparent a couple new issues that didn't really get considered in the first round of discussion (at least I don't recall that they did). To restate the issue: there was a question about whether an index to an array that identified a single element only (i.e., not a slice, nor an incomplete index, e.g. x[3] where x is two dimensional) should return a Python scalar or a rank-0 array. Currently Numeric is inconsistent on this point. One usually gets scalars, but on some occasions, rank-0 arrays are returned. Good arguments are to be had for either alternative. The primary advantage of returning rank-0 arrays is that they reduce the need for conditional code checking to see if a result is a scalar or an array. At the end of the discussion it was decided to have numarray return rank-0 arrays in all instances of single item indexing. Since then, a couple potential snags have arisen. I've already discussed some of these with Paul Dubois and Eric Jones. I'd like a little wider input before making a final (or at least experimental) decision. If we return rank-0 arrays, what should repr return for rank-0 arrays. My initial impression is that the following is highly undesirable for a interactive session, but maybe it is just me:

...

...

x = arange(10) x[2] array(2)

We, of course, could arrange __repr__ to return "2" instead, in other words print the simple scalar for all cases of rank-0 arrays. This would yield the expected output in the above example. Nevertheless, isn't it violating the intent of repr? Are there other examples where Python uses repr in a similar, misleading manner? But perhaps most feel that returning array(2) is perfectly acceptable and won't annoy users. I am curious about what people think about this. The second issue is an efficiency one. Currently numarray uses Python objects for arrays. If we return rank-0 arrays for single item indexing, then some naive uses of larger arrays as sequences may lead to an enormous number of array objects to be created. True, there will be equivalent means of doing the same operation that won't result in massive object creations (such as specifically converting an array to a list, which would be done much faster). Is this a serious problem? These two issues led us to question whether we should indeed return rank-0 arrays. We can live with either solution. But we do want to make the right choice. We also know that both functionalities must exist, e.g., indexing for scalars and indexing for rank-0 arrays and we will provide both. The issue is what indexing syntax returns. One argument is that it is not a great burden on programmers to use a method (or other means) to obtain a rank-0 array always if that is important for the code they are writing and that we should make the indexing syntax return what most users (especially less expert ones) intuitively expect (scalars I presume). But others feel it is just as important for the syntax that a progammer uses to be as simple as the interactive user expects (instead of something like x.getindexasarrayalways(2,4,1) [well, with a much better, and shorter, name]) Do either of these issues change anyone's opinion? If people still want rank-0 arrays, what should repr do? Perry Greenfield