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Re: units issues

On 2017-05-23 17:55, Doug Henderson wrote:
> On 23 May 2017 at 15:49, Brian Inglis wrote:
>> Updating the currencies only when setup is run seems to me to be
>> insufficient if users want to use current currency conversions.
> Currencies needs to be split to a different package from non-currency
> units. Non-currency units is very static, whereas most currencies
> changes daily. In the absence of updates, non-currency units are still
> useful; but currencies are incorrect in most cases, and increasingly
> so as time pass.
> It is difficult to predict user requirements based on current package
> dependencies as non-currency units and currencies are likely used by
> almost disjoint sets of packages. Users of non-currency units should
> not be burdened by the complexities of currencies. But if they do need
> currencies, they should be up to date.
> A possible solution is to check the currency of the currency data on
> library initialization or each use by comparing the current date with
> the data's date of update. When the data is stale, automatically
> update it if possible, or notify the user of the problem.

It's a command line utility from GNU with currency conversion factors in
a separate definition file included from the main file, updated by a
Python script, which downloads an RSS XML file of current (Euro) rates
from a free source with a permissive licence, and converts it to
definitions acceptable to the utility, overwriting the existing file.

The main issues are that, as currently implemented, currency rates are
updated automatically by a postinstall script only when setup is run;
setup may be running in an environment without external access, so the
postinstall script will generate an error; users may not want or care
about currency updates; and the postinstall script uses find to avoid
updating if there is no currency file, or it has been updated recently.

One option to deal with this is update the package to install a zero
length currency definitions file, so currency conversions are not
defined, but the program has no issues, and drop the permanent
postinstall script to perform updates.
Then announce and document that users who want updated currency
conversion rates need to run the update script from the command line, a
profile script, cron job, or Windows Scheduled Task, as is desirable if
they use currency conversions.

There are also issues with the Python update script, as the currency
source site cert expired recently, causing the update and postinstall
scripts to fail, with no workaround other than a replacement or patch;
and a poster has problems using the update script with Windows proxies,
which I have addressed to the upstream maintainer for discussion about
If there is no response, I will create a Cygwin update patch and submit
it upstream, but there has been no visible response to issues raised on
the GNU site.

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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