www.digitalmars.com         C & C++   DMDScript  

digitalmars.D - Should we have prettier string printing for exceptions and std elemts?

reply Fra Mecca <me francescomecca.eu> writes:
Hi,
I have noticed that there are elements of core and phobos that 
are pretty ugly when printed via writeln.

One example is container.Array, but also exceptions.

Should we prettify all of them to have a result similar to the 
one in python?
Oct 08 2017
next sibling parent bauss <jj_1337 live.dk> writes:
On Sunday, 8 October 2017 at 21:48:05 UTC, Fra Mecca wrote:

 Hi,
 I have noticed that there are elements of core and phobos that 
 are pretty ugly when printed via writeln.

 One example is container.Array, but also exceptions.

 Should we prettify all of them to have a result similar to the 
 one in python?


I believe we shouldn't; at least not for the default writeln, 
writefln etc.

If anything there should be made alternative functions to do that.
Oct 09 2017
prev sibling next sibling parent jmh530 <john.michael.hall gmail.com> writes:
On Sunday, 8 October 2017 at 21:48:05 UTC, Fra Mecca wrote:

 One example is container.Array


Ideally you would format the container as a string and then 
writeln that. There are some examples in std.format's 
documentation of how to make it prettier. I relied on that to do 
the same for mir's ndslices:
https://github.com/libmir/numir/pull/10
Oct 09 2017
prev sibling parent reply Petar Kirov [ZombineDev] <petar.p.kirov gmail.com> writes:
On Sunday, 8 October 2017 at 21:48:05 UTC, Fra Mecca wrote:

 Hi,
 I have noticed that there are elements of core and phobos that 
 are pretty ugly when printed via writeln.

 One example is container.Array, but also exceptions.

 Should we prettify all of them to have a result similar to the 
 one in python?


This has been previously discussed 
(https://issues.dlang.org/show_bug.cgi?id=13971) and AFAIR the 
opinions were divided.

For one, the only thing necessary to get pretty-printing of the 
elements of a container is to slice it. Slicing a container 
returns a range and since std.format supports printing ranges it 
works out-of-the box.

import std.stdio, std.container;
void main(string[] args)
{
     auto arr = make!(Array!int)(1, 2, 3);
     writeln(arr);
     writeln(arr[]); // slice
}

Array!int(RefCounted!(Payload, 
cast(RefCountedAutoInitialize)0)(RefCountedStore(7F10930E8490)))
[1, 2, 3]

https://run.dlang.io/is/WQiV3P

Another point is that if the container contains many elements 
automatically printing all of them would be ugly, unhelpful and 
slow, while printing its identity (I think the address of the 
RefCountedStore doesn't change on reallocation) may be more 
useful.
Oct 09 2017
parent reply jmh530 <john.michael.hall gmail.com> writes:
On Monday, 9 October 2017 at 17:19:42 UTC, Petar Kirov 
[ZombineDev] wrote:

 Another point is that if the container contains many elements 
 automatically printing all of them would be ugly, unhelpful and 
 slow, while printing its identity (I think the address of the 
 RefCountedStore doesn't change on reallocation) may be more 
 useful.


This relates to your comment in the bugzilla to format with 
'%5r'. This would be similar to using something like head or tail 
in R and the printing the result. I consider that a separate 
issue. It's really easy to handle this in D with UFCS. In Mir, 
you could do slice.select(5).writefln!"%s".
Oct 09 2017
parent reply Petar Kirov [ZombineDev] <petar.p.kirov gmail.com> writes:
On Monday, 9 October 2017 at 17:44:12 UTC, jmh530 wrote:

 On Monday, 9 October 2017 at 17:19:42 UTC, Petar Kirov 
 [ZombineDev] wrote:

 Another point is that if the container contains many elements 
 automatically printing all of them would be ugly, unhelpful 
 and slow, while printing its identity (I think the address of 
 the RefCountedStore doesn't change on reallocation) may be 
 more useful.


 This relates to your comment in the bugzilla to format with 
 '%5r'. This would be similar to using something like head or 
 tail in R and the printing the result. I consider that a 
 separate issue. It's really easy to handle this in D with UFCS. 
 In Mir, you could do slice.select(5).writefln!"%s".


Yes, nowadays I am not so certain that we need a dedicated format 
for printing only some of the elements, as for most containers it 
should be as simple as container[0..5] or container[].take(5). 
What I'm certain though, is that I don't want all my containers 
with millions of elements to have their elements printed by 
default. The std.format code could probably hide them if they're 
too many, but at this point it is better to leave the 
customization to the user. Printing the container type, address 
and length would be most useful default IMO (but in a better 
looking way than what we have now for std.container.array).
Oct 09 2017
parent reply bauss <jj_1337 live.dk> writes:
On Monday, 9 October 2017 at 18:52:03 UTC, Petar Kirov 
[ZombineDev] wrote:

 On Monday, 9 October 2017 at 17:44:12 UTC, jmh530 wrote:

 On Monday, 9 October 2017 at 17:19:42 UTC, Petar Kirov 
 [ZombineDev] wrote:






Printing the container

 type, address and length would be most useful default IMO (but 
 in a better looking way than what we have now for 
 std.container.array).


That's your opinion though; IMO I'd rather have the elements 
printed by default.

It's all subjective and thus there's no real reason for one or 
the other.



 Oct 10 2017



  parent  Seb <seb wilzba.ch>  writes:


On Tuesday, 10 October 2017 at 11:17:09 UTC, bauss wrote:

 On Monday, 9 October 2017 at 18:52:03 UTC, Petar Kirov 
 [ZombineDev] wrote:

 On Monday, 9 October 2017 at 17:44:12 UTC, jmh530 wrote:

 On Monday, 9 October 2017 at 17:19:42 UTC, Petar Kirov 
 [ZombineDev] wrote:






 Printing the container

 type, address and length would be most useful default IMO (but 
 in a better looking way than what we have now for 
 std.container.array).


 That's your opinion though; IMO I'd rather have the elements 
 printed by default.

 It's all subjective and thus there's no real reason for one or 
 the other.


FWIW I tried to propose a `dump` function one year ago [1].
There has never been a great interest in it though as while using 
`writeln` is a bit annoying (e.g. no spaces, no variable names) 
apparently all core people got used to it already ;-)

If someone considers to add a pretty printing method he/she, this 
new symbol could also be very useful for single elements too (and 
thus gain chances in its acceptance).

[1] 
https://github.com/dlang/phobos/pull/4318#issuecomment-241819997



 Oct 10 2017