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Groups > comp.lang.python > #67717
| From | Marko Rauhamaa <marko@pacujo.net> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Functional programming |
| Date | 2014-03-04 22:50 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <8738ixofhl.fsf@elektro.pacujo.net> (permalink) |
| References | (13 earlier) <mailman.7695.1393913099.18130.python-list@python.org> <53159540$0$2923$c3e8da3$76491128@news.astraweb.com> <mailman.7700.1393930643.18130.python-list@python.org> <87bnxloibq.fsf@elektro.pacujo.net> <mailman.7737.1393963318.18130.python-list@python.org> |
Chris Angelico <rosuav@gmail.com>:
> On Wed, Mar 5, 2014 at 6:49 AM, Marko Rauhamaa <marko@pacujo.net> wrote:
>> public ConnectionPool(int maxConnections, String url) throws SQLException {
>> try {
>> super(() -> {
>> try {
>> return DriverManager.getConnection(url);
>> } catch ( SQLException ex ) {
>> throw new WrappedSqlException(ex);
>> }
>> }, maxConnections);
>> } catch (WrappedSqlException wse) {
>> throw wse.getSqlException();
>> }
>> }
>>
>> ===JAVA END=============================================================
>
> You're not doing the same thing, though. The Java rigmarole is to
> ensure that an SQLException thrown in getConnection will propagate up,
> despite (presumably) something inside the equivalent of
> super().__init__ that swallows SQLExceptions. Of course it looks
> tidier when you don't do the messy bit.
See <URL: http://stackoverflow.com/questions/14039995/
java-8-mandatory-checked-exceptions-handling-in-lambd
a-expressions-for-standard>.
The "rigmarole" is trying to get around Java's mandatory exception
handling limitations, which Python doesn't have.
You are not allowed to pass a lambda to the super constructor that
throws an SQLException. To get around the limitation, a RuntimeException
wrapper is created to smuggle the SQLException through the compiler's
defenses. Any code is free to throw a RuntimeException.
I don't know, though, if this is that good of an example. I don't know
if the lambda gets called within the constructor or, as I would guess,
whenever a new connection is needed. The whole wrapping exercise would
be for nothing, then.
Here's a more prosaic example (probably contains errors):
===JAVA BEGIN===========================================================
private Map<TaxpayerIdNumber, Map<FormId, Form>> filings =
new TreeMap<TaxpayerIdNumber, Map<FormId, Form>>();
class FormFiling {
public FormFiling(TaxpayerIdNumber taxpayerId, Form form) {
this.taxpayerId = taxpayerId;
this.form = form;
}
public TaxpayerIdNumber getTaxpayerId() { return taxpayerId; }
public Form getForm() { return form; }
private TaxpayerIdNumber taxpayerId;
private Form form;
};
List<FormFiling> getForms(FormId formId)
{
List<FormFiling> forms = new LinkedList<FormFiling>();
for (Map.Entry<TaxpayerIdNumber, Map<FormId, Form>> payerEntry :
filings.entrySet()) {
TaxpayerIdNumber taxpayerId = payerEntry.getKey();
Map<FormId, Form> filing = payerEntry.getValue();
if (filing.containsKey(formId))
forms.add(new FormFiling(taxpayerId, filing.get(formId)))
}
return forms;
}
===JAVA END=============================================================
===PYTHON BEGIN=========================================================
filings = {}
def getForms(formId):
forms = []
for taxpayerId, filing in filings.iteritems():
if formId in filing:
forms.append((taxpayerId, filing[formId]))
return forms
===PYTHON END===========================================================
or:
===PYTHON BEGIN=========================================================
filings = {}
def getForms(formId):
return ((taxpayerId, filing[formId])
for (taxpayerId, filing) in filings.iteritems()
if formId in filing)
===PYTHON END===========================================================
Marko
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Re: Functional programming Ned Batchelder <ned@nedbatchelder.com> - 2014-03-02 20:27 -0500
Re: Functional programming Rustom Mody <rustompmody@gmail.com> - 2014-03-03 03:45 -0800
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-03 23:20 +1100
Re: Functional programming Rustom Mody <rustompmody@gmail.com> - 2014-03-03 05:48 -0800
Re: Functional programming Rustom Mody <rustompmody@gmail.com> - 2014-03-03 05:51 -0800
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-04 01:00 +1100
Re: Functional programming Rustom Mody <rustompmody@gmail.com> - 2014-03-03 06:08 -0800
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-04 01:23 +1100
Re: Functional programming Rustom Mody <rustompmody@gmail.com> - 2014-03-03 06:38 -0800
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-04 02:01 +1100
Re: Functional programming Rustom Mody <rustompmody@gmail.com> - 2014-03-03 07:28 -0800
Re: Functional programming Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-03 17:27 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-04 05:37 +1100
Re: Functional programming Steven D'Aprano <steve@pearwood.info> - 2014-03-04 05:35 +0000
Re: Functional programming Rustom Mody <rustompmody@gmail.com> - 2014-03-03 21:59 -0800
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-04 17:04 +1100
Re: Functional programming Rustom Mody <rustompmody@gmail.com> - 2014-03-03 22:20 -0800
Re: Functional programming Steven D'Aprano <steve@pearwood.info> - 2014-03-04 08:56 +0000
Re: Functional programming Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2014-03-04 11:56 +0100
Re: Functional programming Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 11:47 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 00:01 +1100
OT Sine Rule [was Re: Functional programming] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 14:25 +0000
Re: OT Sine Rule [was Re: Functional programming] Tim Chase <python.list@tim.thechases.com> - 2014-03-04 08:37 -0600
Re: OT Sine Rule [was Re: Functional programming] Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-04 14:42 +0000
Re: OT Sine Rule [was Re: Functional programming] Chris Angelico <rosuav@gmail.com> - 2014-03-05 02:06 +1100
Re: OT Sine Rule [was Re: Functional programming] Tim Chase <python.list@tim.thechases.com> - 2014-03-04 09:21 -0600
Re: Functional programming Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2014-03-05 09:59 +0100
Re: Functional programming Marko Rauhamaa <marko@pacujo.net> - 2014-03-04 21:49 +0200
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 07:01 +1100
Re: Functional programming Marko Rauhamaa <marko@pacujo.net> - 2014-03-04 22:50 +0200
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 08:06 +1100
Re: Functional programming Marko Rauhamaa <marko@pacujo.net> - 2014-03-04 23:21 +0200
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 08:26 +1100
Re: Functional programming Marko Rauhamaa <marko@pacujo.net> - 2014-03-04 23:43 +0200
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 08:52 +1100
Re: Functional programming Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-03-05 12:57 +1300
Re: Functional programming Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 02:11 +0200
Re: Functional programming "BartC" <bc@freeuk.com> - 2014-03-04 13:30 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 00:47 +1100
Re: Functional programming Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-04 14:05 +0000
Re: Functional programming Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 14:55 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 02:13 +1100
Re: Functional programming MRAB <python@mrabarnett.plus.com> - 2014-03-04 17:07 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 01:17 +1100
Re: Functional programming Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 15:18 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 02:28 +1100
Re: Functional programming Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 15:45 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 03:04 +1100
Re: Functional programming Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2014-03-05 10:09 +0100
Re: Functional programming "BartC" <bc@freeuk.com> - 2014-03-05 11:28 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-05 23:04 +1100
Re: Functional programming Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 14:11 +0200
Re: Functional programming Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-03-04 11:06 +1300
Re: Functional programming Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 09:31 +1100
Re: Functional programming Grant Edwards <invalid@invalid.invalid> - 2014-03-04 14:59 +0000
Re: Functional programming Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 15:22 +0000
Re: Functional programming Chris Angelico <rosuav@gmail.com> - 2014-03-04 09:42 +1100
Re: Functional programming Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 10:52 +1100
Re: Functional programming "BartC" <bc@freeuk.com> - 2014-03-04 09:41 +0000
Re: Functional programming 88888 Dihedral <dihedral88888@gmail.com> - 2014-03-03 16:35 -0800
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