Issue1756

The Jython documentation on your website states:

"The array module exports two factory functions:

array(type, sequence)
zeros(type, length)"

If I type:
arr = zeros('i',10)
I get the error:
'zeros' is not defined

Chapter 2 of the Jython book linked-to on your website at:

http://www.jython.org/jythonbook/en/1.0/DataTypes.html#jython-specific-collections

states in Listing 2-30:

arr2 = zeros(6, 'i')

noting that the ordering of the type and length are reversed. Using this ordering doesn't work either.

Thus, as a new user I am left wondering which way round the type and length are and whether this function is supported at all.

The confusion seems to stem from the fact that jarray and array are different modules. Both are working.

>>> from array import zeros
>>> zeros('i',10)
array('i', [0, 0, 0, 0, 0, 0, 0, 0, 0, 0])

>>> from jarray import zeros
>>> zeros(10, 'i')
array('i', [0, 0, 0, 0, 0, 0, 0, 0, 0, 0])

I don't see an issue here. It is implicit from code listing 2-28 and from the descriptive text that the zeros method is in the jarray module: "Another useful feature of the jarray is that we can create empty arrays if we wish by using the zeros() method."

I think this issue should be closed as "rejected".

Assigning to Josh: he should decide if the book needs to clearer on this matter.

Listing 2-29 and 2-30 seem to be incorrect, as zeros is being invoked with the parameters backwards.  I will need to patch this documentation to repair these two examples.

It's worth noting the following:

The jarray module is mostly phased out, but it is still has one
constructor function - zeros - that is not directly available in the
array module.

The equivalent of
jarray.zeros(n, typecode)
is
array.array(typecode, itertools.repeat(0, n))

however itertools.repeat does not define __len__ and therefore we
have to first build out the zero sequence separately, then copy
over. This overhead could be significant for large arrays.

Also I should point out that the Jython book is available at https://github.com/jython/book

and is currently being built at http://jython.readthedocs.org/en/latest/

So any PRs that are merged into the above repo will automatically get built out. We should do that.

Note there is at least one chapter (http://jython.readthedocs.org/en/latest/chapter19/) where we are using RST that is not buildable via RTD. That should be a simple fix too.