Re: List Comprehension equivalent
On Sat, 2017-03-18 at 11:38 +, thedeemon via Digitalmars-d-learn wrote: > On Saturday, 18 March 2017 at 11:09:34 UTC, Russel Winder wrote: > > Is this foldr or foldl' ? > > It's a left fold of course, having foldr by default in eager > language would be awkward. I would expect foldl, but there is no "of course" of the semantics of fold (or reduce) with any library. People have been known to implement the wrong thing. -- Russel. = Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net 41 Buckmaster Roadm: +44 7770 465 077 xmpp: rus...@winder.org.uk London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder signature.asc Description: This is a digitally signed message part
Re: List Comprehension equivalent
On Saturday, 18 March 2017 at 11:09:34 UTC, Russel Winder wrote: Is this foldr or foldl' ? It's a left fold of course, having foldr by default in eager language would be awkward.
Re: List Comprehension equivalent
On Fri, 2017-03-17 at 12:32 -0700, Ali Çehreli via Digitalmars-d-learn wrote: > On 03/17/2017 12:21 PM, John Colvin wrote: > > On Friday, 17 March 2017 at 19:08:36 UTC, Russel Winder wrote: > > >> Rust ownership problems > >> seem to be a doddle compared to this problem. > > It sometimes feels like that but we don't want to lose you. :) Rust has a lot going for it, some of it hype, agreed, that has transformed into a vibrant user community. Go also has a vibrant user community, at least in London. Even C++ has a vibrant user community in London – reinvigorated and spurred on by Phil Nash, JetBrains, and C++17. In the face of Rust, Go, and C++ activity in London, and D's failure to get any user community activity going, it is hard to not shift away from D to Rust, Go, and C++. > > reduce is a free function in std.algorithm. Just import it and > you're > > away. > > 'fold' (a relatively recent addition) is recommended is almost all > cases > because it actually works with chained range syntax. > > https://dlang.org/phobos/std_algorithm_iteration.html#fold > The whole inject/reduce/fold/foldr/foldl/foldl' naming and API definition thing is a mess. But then that is 50 years of programming language evolution for you. :-) -- Russel. = Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net 41 Buckmaster Roadm: +44 7770 465 077 xmpp: rus...@winder.org.uk London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder signature.asc Description: This is a digitally signed message part
Re: List Comprehension equivalent
On Fri, 2017-03-17 at 12:29 -0700, H. S. Teoh via Digitalmars-d-learn wrote: > […] > Also, there is now a variant of reduce called `fold`, that has a > nicer > order of parameters, i.e., you can use it in UFCS chains: > > myData.map!(a => transform(a)) > .fold!((a,b) => a + b)(0); > > whereas `reduce` won't work this way because it has an incompatible > order of parameters. Is this foldr or foldl' ? -- Russel. = Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net 41 Buckmaster Roadm: +44 7770 465 077 xmpp: rus...@winder.org.uk London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder signature.asc Description: This is a digitally signed message part
Re: List Comprehension equivalent
On Fri, Mar 17, 2017 at 07:21:50PM +, John Colvin via Digitalmars-d-learn wrote: [...] > reduce is a free function in std.algorithm. Just import it and you're > away. [...] Also, there is now a variant of reduce called `fold`, that has a nicer order of parameters, i.e., you can use it in UFCS chains: myData.map!(a => transform(a)) .fold!((a,b) => a + b)(0); whereas `reduce` won't work this way because it has an incompatible order of parameters. T -- There are three kinds of people in the world: those who can count, and those who can't.
Re: List Comprehension equivalent
On 03/17/2017 12:21 PM, John Colvin wrote: > On Friday, 17 March 2017 at 19:08:36 UTC, Russel Winder wrote: >> Rust ownership problems >> seem to be a doddle compared to this problem. It sometimes feels like that but we don't want to lose you. :) > reduce is a free function in std.algorithm. Just import it and you're > away. 'fold' (a relatively recent addition) is recommended is almost all cases because it actually works with chained range syntax. https://dlang.org/phobos/std_algorithm_iteration.html#fold Ali
Re: List Comprehension equivalent
On Fri, 2017-03-17 at 19:21 +, John Colvin via Digitalmars-d-learn
wrote:
> […]
>
> reduce is a free function in std.algorithm. Just import it and
> you're away. Anyway, is this what you wanted?
>
> string[] blah(string[][string] groups)
> {
> import std.algorithm : map, joiner;
> import std.array : array, byPair;
> return groups.byPair()
> .map!(a =>
> a[1].sort!debianPackageNumberComparator()[0..$-1])
> .joiner
> .array;
> }
Yes it is. I had failed to import joiner in previous experiments.
I feel sufficiently like an idiot now, that I shall imbibe excessively
of the Ricard.
However on the upside the code work very declaratively. :-)
--
Russel.
=
Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net
41 Buckmaster Roadm: +44 7770 465 077 xmpp: rus...@winder.org.uk
London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder
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Re: List Comprehension equivalent
On Friday, 17 March 2017 at 19:08:36 UTC, Russel Winder wrote:
On Fri, 2017-03-17 at 17:51 +, Jerry via
Digitalmars-d-learn wrote:
On Friday, 17 March 2017 at 17:13:48 UTC, Russel Winder wrote:
> I have a bit of code:
>
> string[] returnValue;
>foreach(string key, string[] value; groups) {
>returnValue ~=
> value.sort!debianPackageNumberComparator()[0..$-1].array;
>}
>return returnValue;
>
> [...]
You forgot a ! on the map call.
.map!((Tuple!(string, string[]) a) =>
a[1].sort!debianPackageNumberComparator()[0..$-1])
How embarrassed am I? :-)
However, the result of the map appears to be untransformable to
anything related to a sequence of string. The result is some
type that
renders as a sequence of sequence using writeln but how to
reduce it to
a sequence? reduce isn't defined on MapResult and if I
transform to an
array reduce is not defined on SortedRange[]. Rust ownership
problems
seem to be a doddle compared to this problem.
reduce is a free function in std.algorithm. Just import it and
you're away. Anyway, is this what you wanted?
string[] blah(string[][string] groups)
{
import std.algorithm : map, joiner;
import std.array : array, byPair;
return groups.byPair()
.map!(a =>
a[1].sort!debianPackageNumberComparator()[0..$-1])
.joiner
.array;
}
Re: List Comprehension equivalent
On Fri, 2017-03-17 at 17:51 +, Jerry via Digitalmars-d-learn wrote:
> On Friday, 17 March 2017 at 17:13:48 UTC, Russel Winder wrote:
> > I have a bit of code:
> >
> > string[] returnValue;
> > foreach(string key, string[] value; groups) {
> > returnValue ~=
> > value.sort!debianPackageNumberComparator()[0..$-1].array;
> > }
> > return returnValue;
> >
> > [...]
>
> You forgot a ! on the map call.
>
> .map!((Tuple!(string, string[]) a) =>
> a[1].sort!debianPackageNumberComparator()[0..$-1])
How embarrassed am I? :-)
However, the result of the map appears to be untransformable to
anything related to a sequence of string. The result is some type that
renders as a sequence of sequence using writeln but how to reduce it to
a sequence? reduce isn't defined on MapResult and if I transform to an
array reduce is not defined on SortedRange[]. Rust ownership problems
seem to be a doddle compared to this problem.
--
Russel.
=
Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net
41 Buckmaster Roadm: +44 7770 465 077 xmpp: rus...@winder.org.uk
London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder
signature.asc
Description: This is a digitally signed message part
Re: List Comprehension equivalent
On 03/17/2017 10:51 AM, Jerry wrote:
On Friday, 17 March 2017 at 17:13:48 UTC, Russel Winder wrote:
I have a bit of code:
string[] returnValue;
foreach(string key, string[] value; groups) {
returnValue ~=
value.sort!debianPackageNumberComparator()[0..$-1].array;
}
return returnValue;
[...]
You forgot a ! on the map call.
.map!((Tuple!(string, string[]) a) =>
a[1].sort!debianPackageNumberComparator()[0..$-1])
This happens to me too. I think the compiler can generate a warning when
mandatory template parameters are not provided. Submitted:
https://issues.dlang.org/show_bug.cgi?id=17263
Ali
Re: List Comprehension equivalent
On Friday, 17 March 2017 at 17:13:48 UTC, Russel Winder wrote:
I have a bit of code:
string[] returnValue;
foreach(string key, string[] value; groups) {
returnValue ~=
value.sort!debianPackageNumberComparator()[0..$-1].array;
}
return returnValue;
[...]
You forgot a ! on the map call.
.map!((Tuple!(string, string[]) a) =>
a[1].sort!debianPackageNumberComparator()[0..$-1])
