On Sat, 13 Oct 2012, Allin Cottrell wrote:
> On Sat, 13 Oct 2012, Logan Kelly wrote:
>
>> I am using GRETL 1.9.9 on a Win 7 64bit machine. I found a quirk that may
>> be a bug. I found that
>>
>> bundle BundleOfMatrixs
>> matrix BundleOfMatrixs["test"] = {}
>> matrix test = {1,2,3,4}
>> BundleOfMatrixs["test"] |= test
>>
>> yields the following error message
>>
>> '|=' : only defined for matrices
>>
>> Error executing script: halting
>>> BundleOfMatrixs["test"] |= test
>>
>> but that
>>
>> bundle BundleOfMatrixs
>> matrix BundleOfMatrixs["test"] = {}
>> matrix test = {1,2,3,4}
>> BundleOfMatrixs["test"] = BundleOfMatrixs["test"]|test
>>
>> works just fine.
>
> Hmm, not sure this is a bug. This basic idea with bundles is that
> if you want to do anything with a matrix (or any other sort of
> object) from inside the bundle you have to extract it first (which
> makes a copy of the object).
>
> At first I was a little surprised that even your second
> formulation worked, but on reflection it's OK: on the right hand
> side, BundleOfMatrixs["test"] produces an anonymous matrix which
> is a copy of the one in the bundle, to which you concatenate
> another matrix; then the "=" operation replaces the bundle content
> under the key "test" with the new right-hand side matrix. That is,
> your second version is an acceptable variant of the canonical form
>
> matrix m = BundleOfMatrixs["test"] # extract
> m |= {1,2,3,4} # modify
> BundleOfMatrixs["test"] = m # re-assign
>
> I guess one could argue that your first formulation should be
> taken as shorthand for your second, but I have to say it doesn't
> "look right" to me; I would not have expected it to work -- though
> I admit I'd have had difficulty predicting the error message.
I think I can justify the present behavior one step further. The
thing is that the left-hand side expression BundleOfMatrixs["test"]
just _happens to_ be associated with a matrix, in context; it can
accept any assignment, since the type that falls under a given key
can be changed. For example:
<hansl>
bundle B
matrix m = {}
B["test"] = m
string s = "foo"
B["test"] = s
print B
</hansl>
This means that a left-hand side term of the form
<bundlename>[<key>]
is of indeterminate type, and so composite operators such as "+="
and "|=", which only work for a subset of types, cannot be used.
Allin Cottrell
