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digitalmars.D.learn - Regarding std.array.Appender

reply bearophile <bearophileHUGS lycos.com> writes:
Do you know why std.array.Appender defines a "put" method instead of
overloading the "~=" operator?

Bye and thank you,
bearophile
Feb 29 2012
next sibling parent "Jonathan M Davis" <jmdavisProg gmx.com> writes:
On Wednesday, February 29, 2012 20:25:35 bearophile wrote:
 Do you know why std.array.Appender defines a "put" method instead of
 overloading the "~=" operator?

put is a function on output ranges, and Appender is an output range. - Jonathan M Davis
Feb 29 2012
prev sibling next sibling parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
Luckily you can always use alias this and overload opCatAssign. 'alias
this' is a great tool for customizing APIs. :)
Feb 29 2012
prev sibling next sibling parent reply "Jonathan M Davis" <jmdavisProg gmx.com> writes:
On Wednesday, February 29, 2012 20:53:04 Jonathan M Davis wrote:
 On Wednesday, February 29, 2012 20:25:35 bearophile wrote:
 Do you know why std.array.Appender defines a "put" method instead of
 overloading the "~=" operator?

put is a function on output ranges, and Appender is an output range.

Also, given that it doesn't define ~ (and it wouldn't really make sense for it to), it would be very weird IMHO to define ~=. - Jonathan M Davis
Feb 29 2012
parent reply bearophile <bearophileHUGS lycos.com> writes:
Jonathan M Davis:

 put is a function on output ranges, and Appender is an output range.

Also, given that it doesn't define ~ (and it wouldn't really make sense for it to), it would be very weird IMHO to define ~=.

I don't understand why that's weird. In Java you can't overload an append operator, so using a method is right. But for me it's weird that Appender doesn't use the D operator to _append_. I sometimes use "add" instead of "put" by mistake, forgetting the right method name, because I find it quite unnatural. If Appender needs a put, then I suggest to give it both "put" method and "~=" operator. Bye, bearophile
Feb 29 2012
next sibling parent reply Jonathan M Davis <jmdavisProg gmx.com> writes:
On Thursday, March 01, 2012 03:29:06 Adam D. Ruppe wrote:
 On Thursday, 1 March 2012 at 02:23:55 UTC, bearophile wrote:
 But for me it's weird that Appender doesn't use the D operator
 to _append_.  [...] I suggest to give it both "put" method and
 "~=" operator.

I agree entirely. Another annoyance is if you have a function that works on regular arrays, you probably used ~=. But you decide to switch to Appender to try for a speed boost. Now you have to change all the usage too, since the interfaces are incompatible!

True, but it can't do all of the other operations that array can do either. It's an output range, not an array. And odds are that it's going to be refactored such that it doesn't even contain an array internally anymore, beacause that's an inefficient way to implement appending. Someone (Robert Jacques IIRC, but I'd have to check) has already created such an implementation, and there's a decent chance that it's going to make it into Phobos. So, I'm not sure that treating Appender as an array is really a good idea in the first place. If you want the truly generic approach, then treat is an output range. - Jonathan M Davis
Feb 29 2012
parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 02/29/2012 08:28 PM, James Miller wrote:

 I understand that Appenders aren't arrays, and should not be used as
 such, but you /can/ use an array as an Appender.

Yes you can but whatever you put() into the array is immediately popFront()'ed from the array. ;) You must use a temporary surrogate slice: import std.stdio; import std.range; void main() { int[] array = [ 1, 2, 3 ]; int[] slice = array; put(slice, 100); // <-- slice shrinks! :) } slice.length is 2 and array.length is 3.
 At some point, you
 have to concede design purity to convenience, otherwise you have a
 language that is actively hostile to changing designs.

Agreed. Ali
Feb 29 2012
prev sibling next sibling parent "Adam D. Ruppe" <destructionator gmail.com> writes:
On Thursday, 1 March 2012 at 02:44:35 UTC, Jonathan M Davis wrote:
 True, but it can't do all of the other operations that array 
 can do either.

Yeah, but the one operation it replaces, ~=, can be done on an array. If you're trying to convert array code to Appender for speed, most likely you're going to be replacing a bunch of ~= calls. It's ok if the other op don't compile, but this one really should. Appender, regardless of the internal representation vs array is a speed optimization; an implementation detail.
 It's an output range, not an array.

It's also an Appender, though. I think it is a little silly to have an Appender to which you can't /append/. (put is great too, don't get me wrong, but so is ~=).
Feb 29 2012
prev sibling next sibling parent James Miller <james aatch.net> writes:
On 1 March 2012 15:49, Adam D. Ruppe <destructionator gmail.com> wrote:
 On Thursday, 1 March 2012 at 02:44:35 UTC, Jonathan M Davis wrote:
 True, but it can't do all of the other operations that array can do
 either.

Yeah, but the one operation it replaces, ~=, can be done on an array. If you're trying to convert array code to Appender for speed, most likely you're going to be replacing a bunch of ~= calls. It's ok if the other op don't compile, but this one really should. Appender, regardless of the internal representation vs array is a speed optimization; an implementation detail.
 It's an output range, not an array.

It's also an Appender, though. I think it is a little silly to have an Appender to which you can't /append/. (put is great too, don't get me wrong, but so is ~=).

I can see both sides, but I'm on Adam's side here. While all the other opOpAssign functions are defined in terms of their opBinary equivalent (e.g, += is 'add and assign'), ~= is essentially an operator in its own right, specifically an append (as opposed to '~' which is concatenate). Having both ~= and .put() would be fine, and would make switching from arrays to Appenders much easier. I understand that Appenders aren't arrays, and should not be used as such, but you /can/ use an array as an Appender. At some point, you have to concede design purity to convenience, otherwise you have a language that is actively hostile to changing designs. *In best "nagging wife" voice* "You should have used an Appender from the start. Now you have to go change all that code. Its your own fault really."... -- James Miller
Feb 29 2012
prev sibling next sibling parent Timon Gehr <timon.gehr gmx.ch> writes:
On 03/01/2012 03:40 AM, Jonathan M Davis wrote:
 On Wednesday, February 29, 2012 21:23:54 bearophile wrote:
 Jonathan M Davis:
 put is a function on output ranges, and Appender is an output range.

Also, given that it doesn't define ~ (and it wouldn't really make sense for it to), it would be very weird IMHO to define ~=.

I don't understand why that's weird. In Java you can't overload an append operator, so using a method is right. But for me it's weird that Appender doesn't use the D operator to _append_. I sometimes use "add" instead of "put" by mistake, forgetting the right method name, because I find it quite unnatural. If Appender needs a put, then I suggest to give it both "put" method and "~=" operator.

Would you define += without defining +? Or *= without defining *? It strikes me as a misuse of operator overloading if you have an opOpAssign without its corresponding opBinary. - Jonathan M Davis

It is not the same thing. a=a~b has different semantics from a~=b;
Mar 01 2012
prev sibling parent =?UTF-8?B?U8O2bmtlIEx1ZHdpZw==?= <ludwig informatik.uni-luebeck.de> writes:
Am 01.03.2012 03:40, schrieb Jonathan M Davis:
 On Wednesday, February 29, 2012 21:23:54 bearophile wrote:
 Jonathan M Davis:
 put is a function on output ranges, and Appender is an output range.

Also, given that it doesn't define ~ (and it wouldn't really make sense for it to), it would be very weird IMHO to define ~=.

I don't understand why that's weird. In Java you can't overload an append operator, so using a method is right. But for me it's weird that Appender doesn't use the D operator to _append_. I sometimes use "add" instead of "put" by mistake, forgetting the right method name, because I find it quite unnatural. If Appender needs a put, then I suggest to give it both "put" method and "~=" operator.

Would you define += without defining +? Or *= without defining *? It strikes me as a misuse of operator overloading if you have an opOpAssign without its corresponding opBinary. - Jonathan M Davis

Consider matrix * vector and matrix *= vector for an opposite example.
Mar 01 2012
prev sibling next sibling parent "Adam D. Ruppe" <destructionator gmail.com> writes:
On Thursday, 1 March 2012 at 02:23:55 UTC, bearophile wrote:
 But for me it's weird that Appender doesn't use the D operator 
 to _append_.  [...] I suggest to give it both "put" method and 
 "~=" operator.

I agree entirely. Another annoyance is if you have a function that works on regular arrays, you probably used ~=. But you decide to switch to Appender to try for a speed boost. Now you have to change all the usage too, since the interfaces are incompatible!
Feb 29 2012
prev sibling next sibling parent Jonathan M Davis <jmdavisProg gmx.com> writes:
On Wednesday, February 29, 2012 21:23:54 bearophile wrote:
 Jonathan M Davis:
 put is a function on output ranges, and Appender is an output range.

Also, given that it doesn't define ~ (and it wouldn't really make sense for it to), it would be very weird IMHO to define ~=.

I don't understand why that's weird. In Java you can't overload an append operator, so using a method is right. But for me it's weird that Appender doesn't use the D operator to _append_. I sometimes use "add" instead of "put" by mistake, forgetting the right method name, because I find it quite unnatural. If Appender needs a put, then I suggest to give it both "put" method and "~=" operator.

Would you define += without defining +? Or *= without defining *? It strikes me as a misuse of operator overloading if you have an opOpAssign without its corresponding opBinary. - Jonathan M Davis
Feb 29 2012
prev sibling parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 29 Feb 2012 20:25:35 -0500, bearophile <bearophileHUGS lycos.com>  
wrote:

 Do you know why std.array.Appender defines a "put" method instead of  
 overloading the "~=" operator?

It should (in addition to put). I see you have already filed an enhancement. http://d.puremagic.com/issues/show_bug.cgi?id=4287 -Steve
Mar 05 2012