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digitalmars.D - foreach

reply Sam S E <eisenstat.aa sympatioco.ca> writes:
Does foreach use delegates? Isn't that unnecessary overhead?
--Sam
Nov 22 2008
next sibling parent reply "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


It does use delegates, for iterating over most types.  When iterating
over arrays, the compiler turns it into a sort of for loop instead.

Is it unnecessary overhead?  It's not always as fast as it could be,
but unless someone can figure out some other way of implementing it,
it's pretty much the best we can get.

How about iterator objects, like in C++ or Java?  Are they unnecessary
overhead?  ;)
Nov 22 2008
parent bearophile <bearophileHUGS lycos.com> writes:
Jarrett Billingsley Wrote:

 When iterating over arrays, the compiler turns it into a sort of for loop
instead.<


Sort of is the key word here :-)
It's not as light as a normal for, but in 98% situations is fine.

Bye,
bearophile
Nov 23 2008
prev sibling next sibling parent reply "Bill Baxter" <wbaxter gmail.com> writes:
On Sun, Nov 23, 2008 at 3:25 PM, Jarrett Billingsley
<jarrett.billingsley gmail.com> wrote:

 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


 It does use delegates, for iterating over most types.  When iterating
 over arrays, the compiler turns it into a sort of for loop instead.

 Is it unnecessary overhead?  It's not always as fast as it could be,
 but unless someone can figure out some other way of implementing it,
 it's pretty much the best we can get.

 How about iterator objects, like in C++ or Java?  Are they unnecessary
 overhead?  ;)


How does delegate overhead compare to the stack thread context switch
overhead in the new Fibers in druntime?

--bb
Nov 23 2008
parent reply Christopher Wright <dhasenan gmail.com> writes:
Bill Baxter wrote:

 On Sun, Nov 23, 2008 at 3:25 PM, Jarrett Billingsley
 <jarrett.billingsley gmail.com> wrote:

 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


 It does use delegates, for iterating over most types.  When iterating
 over arrays, the compiler turns it into a sort of for loop instead.

 Is it unnecessary overhead?  It's not always as fast as it could be,
 but unless someone can figure out some other way of implementing it,
 it's pretty much the best we can get.

 How about iterator objects, like in C++ or Java?  Are they unnecessary
 overhead?  ;)


 
 How does delegate overhead compare to the stack thread context switch
 overhead in the new Fibers in druntime?
 
 --bb


~32 instructions per switch and 4KB allocated for fibers, versus about 2 
instructions and no allocation for delegates.
Nov 23 2008
parent "Bill Baxter" <wbaxter gmail.com> writes:
On Sun, Nov 23, 2008 at 11:26 PM, Christopher Wright <dhasenan gmail.com> wrote:

 Bill Baxter wrote:

 On Sun, Nov 23, 2008 at 3:25 PM, Jarrett Billingsley
 <jarrett.billingsley gmail.com> wrote:

 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa sympatioco.ca>
 wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


 It does use delegates, for iterating over most types.  When iterating
 over arrays, the compiler turns it into a sort of for loop instead.

 Is it unnecessary overhead?  It's not always as fast as it could be,
 but unless someone can figure out some other way of implementing it,
 it's pretty much the best we can get.

 How about iterator objects, like in C++ or Java?  Are they unnecessary
 overhead?  ;)


 How does delegate overhead compare to the stack thread context switch
 overhead in the new Fibers in druntime?

 --bb


 ~32 instructions per switch and 4KB allocated for fibers, versus about 2
 instructions and no allocation for delegates.


Oh, that's a bit worse than I was thinking.  Not a good default
iteration strategy then.  Bummer.

--bb
Nov 23 2008
prev sibling parent reply Sam S E <asdf mailinator.com> writes:
Jarrett Billingsley Wrote:


 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


 
 It does use delegates, for iterating over most types.  When iterating
 over arrays, the compiler turns it into a sort of for loop instead.
 
 Is it unnecessary overhead?  It's not always as fast as it could be,
 but unless someone can figure out some other way of implementing it,
 it's pretty much the best we can get.
 
 How about iterator objects, like in C++ or Java?  Are they unnecessary
 overhead?  ;)


Why not just use a normal for loop; wouldn't it be almost as simple as token
substitution? By 'most types,' do you mean associative arrays or am I
forgetting something? As a mainly C(++) programmer, I don't use iterators when
I don't need to. I don't even use classes when I don't need to.
Nov 23 2008
parent reply "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Sun, Nov 23, 2008 at 10:48 AM, Sam S E <asdf mailinator.com> wrote:

 Jarrett Billingsley Wrote:


 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


 It does use delegates, for iterating over most types.  When iterating
 over arrays, the compiler turns it into a sort of for loop instead.

 Is it unnecessary overhead?  It's not always as fast as it could be,
 but unless someone can figure out some other way of implementing it,
 it's pretty much the best we can get.

 How about iterator objects, like in C++ or Java?  Are they unnecessary
 overhead?  ;)


 Why not just use a normal for loop; wouldn't it be almost as simple as token
substitution? By 'most types,' do you mean associative arrays or am I
forgetting something? As a mainly C(++) programmer, I don't use iterators when
I don't need to. I don't even use classes when I don't need to.


How do you use a for loop to iterate over an associative array whose
implementation is hidden, or a binary tree, or any arbitrary
container, or a sequence or words in a file, or the zipped contents of
two lists, or...

The point of foreach isn't performance, it's flexibility and
abstraction.  As long as you can make an opApply or function which
takes a delegate, you can use the foreach loop with it.  Not
everything is an array.
Nov 23 2008
parent reply Sam S E <asdf mailinator.com> writes:
Jarrett Billingsley Wrote:


 On Sun, Nov 23, 2008 at 10:48 AM, Sam S E <asdf mailinator.com> wrote:

 Jarrett Billingsley Wrote:


 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


 It does use delegates, for iterating over most types.  When iterating
 over arrays, the compiler turns it into a sort of for loop instead.

 Is it unnecessary overhead?  It's not always as fast as it could be,
 but unless someone can figure out some other way of implementing it,
 it's pretty much the best we can get.

 How about iterator objects, like in C++ or Java?  Are they unnecessary
 overhead?  ;)


 Why not just use a normal for loop; wouldn't it be almost as simple as token
substitution? By 'most types,' do you mean associative arrays or am I
forgetting something? As a mainly C(++) programmer, I don't use iterators when
I don't need to. I don't even use classes when I don't need to.


 
 How do you use a for loop to iterate over an associative array whose
 implementation is hidden, or a binary tree, or any arbitrary
 container, or a sequence or words in a file, or the zipped contents of
 two lists, or...
 
 The point of foreach isn't performance, it's flexibility and
 abstraction.  As long as you can make an opApply or function which
 takes a delegate, you can use the foreach loop with it.  Not
 everything is an array.


Where are the docs on opApply?
Nov 23 2008
next sibling parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"Sam S E" wrote

 Where are the docs on opApply?


Kind of hidden.  They are not on the operators page:

http://www.digitalmars.com/d/2.0/statement.html#ForeachStatement

-Steve
Nov 23 2008
prev sibling parent reply Ary Borenszweig <ary esperanto.org.ar> writes:
Sam S E escribió:

 Jarrett Billingsley Wrote:
 

 On Sun, Nov 23, 2008 at 10:48 AM, Sam S E <asdf mailinator.com> wrote:

 Jarrett Billingsley Wrote:


 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


 It does use delegates, for iterating over most types.  When iterating
 over arrays, the compiler turns it into a sort of for loop instead.

 Is it unnecessary overhead?  It's not always as fast as it could be,
 but unless someone can figure out some other way of implementing it,
 it's pretty much the best we can get.

 How about iterator objects, like in C++ or Java?  Are they unnecessary
 overhead?  ;)


 Why not just use a normal for loop; wouldn't it be almost as simple as token
substitution? By 'most types,' do you mean associative arrays or am I
forgetting something? As a mainly C(++) programmer, I don't use iterators when
I don't need to. I don't even use classes when I don't need to.


 How do you use a for loop to iterate over an associative array whose
 implementation is hidden, or a binary tree, or any arbitrary
 container, or a sequence or words in a file, or the zipped contents of
 two lists, or...

 The point of foreach isn't performance, it's flexibility and
 abstraction.  As long as you can make an opApply or function which
 takes a delegate, you can use the foreach loop with it.  Not
 everything is an array.


 
 Where are the docs on opApply?


Search opApply in http://www.digitalmars.com/d/1.0/statement.html

Can't the search in digitalmars.com/d be improved? Searching for 
"opApply" you get ten results which are just questions in the 
newsgroups, and just in the second page you can see the result you 
probably are looking for.

I suggest improving it in this way:
1. Have a map of obvious keywords that people will look for, to precise 
urls. Some examples are: delegate, function, override, virtual, class, 
struct, union, interface, pointer, op*, operator overloading, 
inheritance, final, const, invariant, etc.
2. If the search is exactly one of the keywords, use the map above.
3. Else, use Google Search Engine.

The list might be big, but it can be done if the community helps, and I 
think it will improve a lot the usability of the site.

Actually, the map can be [keyword -> list of urls]. For example, for 
invariant it should point the invariant attribute as well as invariant 
classes.

And don't point me to

http://www.wikiservice.at/wiki4d/wiki.cgi?LanguageSpecification/KeywordIndex

I know it exists, but people how enter the D site (and the above is not 
the D site) will use the search box. Who uses indexes these days when 
you can search and find what you want?
Nov 23 2008
parent reply Ary Borenszweig <ary esperanto.org.ar> writes:
Ary Borenszweig escribió:

 Sam S E escribió:

 Jarrett Billingsley Wrote:


 On Sun, Nov 23, 2008 at 10:48 AM, Sam S E <asdf mailinator.com> wrote:

 Jarrett Billingsley Wrote:


 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E 
 <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead?
 --Sam


 It does use delegates, for iterating over most types.  When iterating
 over arrays, the compiler turns it into a sort of for loop instead.

 Is it unnecessary overhead?  It's not always as fast as it could be,
 but unless someone can figure out some other way of implementing it,
 it's pretty much the best we can get.

 How about iterator objects, like in C++ or Java?  Are they unnecessary
 overhead?  ;)


 Why not just use a normal for loop; wouldn't it be almost as simple 
 as token substitution? By 'most types,' do you mean associative 
 arrays or am I forgetting something? As a mainly C(++) programmer, I 
 don't use iterators when I don't need to. I don't even use classes 
 when I don't need to.


 How do you use a for loop to iterate over an associative array whose
 implementation is hidden, or a binary tree, or any arbitrary
 container, or a sequence or words in a file, or the zipped contents of
 two lists, or...

 The point of foreach isn't performance, it's flexibility and
 abstraction.  As long as you can make an opApply or function which
 takes a delegate, you can use the foreach loop with it.  Not
 everything is an array.


 Where are the docs on opApply?


 
 Search opApply in http://www.digitalmars.com/d/1.0/statement.html
 
 Can't the search in digitalmars.com/d be improved? Searching for 
 "opApply" you get ten results which are just questions in the 
 newsgroups, and just in the second page you can see the result you 
 probably are looking for.
 
 I suggest improving it in this way:
 1. Have a map of obvious keywords that people will look for, to precise 
 urls. Some examples are: delegate, function, override, virtual, class, 
 struct, union, interface, pointer, op*, operator overloading, 
 inheritance, final, const, invariant, etc.
 2. If the search is exactly one of the keywords, use the map above.
 3. Else, use Google Search Engine.
 
 The list might be big, but it can be done if the community helps, and I 
 think it will improve a lot the usability of the site.
 
 Actually, the map can be [keyword -> list of urls]. For example, for 
 invariant it should point the invariant attribute as well as invariant 
 classes.
 
 And don't point me to
 
 http://www.wikiservice.at/wiki4d/wiki.cgi?LanguageSpecification/KeywordIndex 
 
 
 I know it exists, but people how enter the D site (and the above is not 
 the D site) will use the search box. Who uses indexes these days when 
 you can search and find what you want?


Umm... I didn't mean to sound rude or anything. Unfortunately, when 
someone doesn't speak in its native language, he tends to sound rude.

Does anyone else have problems with the search box in digitalmars.com/d ?
Nov 24 2008
next sibling parent Chad J <gamerchad __spam.is.bad__gmail.com> writes:
Ary Borenszweig wrote:

 Ary Borenszweig escribió:

 Sam S E escribió:

 Where are the docs on opApply?


 Search opApply in http://www.digitalmars.com/d/1.0/statement.html

 Can't the search in digitalmars.com/d be improved? Searching for 
 "opApply" you get ten results which are just questions in the 
 newsgroups, and just in the second page you can see the result you 
 probably are looking for.

 I suggest improving it in this way:
 1. Have a map of obvious keywords that people will look for, to 
 precise urls. Some examples are: delegate, function, override, 
 virtual, class, struct, union, interface, pointer, op*, operator 
 overloading, inheritance, final, const, invariant, etc.
 2. If the search is exactly one of the keywords, use the map above.
 3. Else, use Google Search Engine.

 The list might be big, but it can be done if the community helps, and 
 I think it will improve a lot the usability of the site.

 Actually, the map can be [keyword -> list of urls]. For example, for 
 invariant it should point the invariant attribute as well as invariant 
 classes.

 And don't point me to

 http://www.wikiservice.at/wiki4d/wiki.cgi?LanguageSpecification/KeywordIndex 


 I know it exists, but people how enter the D site (and the above is 
 not the D site) will use the search box. Who uses indexes these days 
 when you can search and find what you want?


 
 Umm... I didn't mean to sound rude or anything. Unfortunately, when 
 someone doesn't speak in its native language, he tends to sound rude.
 
 Does anyone else have problems with the search box in digitalmars.com/d ?


Yes.  I think I've mentioned this before too.

And I agree that letting the computer handle the searching instead of 
manually memorizing where to find things in trees of indexed information 
is... just better.  The computer is (erm, /should/ be) better at it than 
we are (most of the time).
Nov 24 2008
prev sibling next sibling parent Jesse Phillips <jessekphillips gmail.com> writes:
On Tue, 25 Nov 2008 00:40:41 -0200, Ary Borenszweig wrote:


 Ary Borenszweig escribió:

 Sam S E escribió:

 Jarrett Billingsley Wrote:


 On Sun, Nov 23, 2008 at 10:48 AM, Sam S E <asdf mailinator.com>
 wrote:

 Jarrett Billingsley Wrote:


 On Sat, Nov 22, 2008 at 11:40 PM, Sam S E
 <eisenstat.aa sympatioco.ca> wrote:

 Does foreach use delegates? Isn't that unnecessary overhead? --Sam


 It does use delegates, for iterating over most types.  When
 iterating over arrays, the compiler turns it into a sort of for
 loop instead.

 Is it unnecessary overhead?  It's not always as fast as it could
 be, but unless someone can figure out some other way of
 implementing it, it's pretty much the best we can get.

 How about iterator objects, like in C++ or Java?  Are they
 unnecessary overhead?  ;)


 Why not just use a normal for loop; wouldn't it be almost as simple
 as token substitution? By 'most types,' do you mean associative
 arrays or am I forgetting something? As a mainly C(++) programmer, I
 don't use iterators when I don't need to. I don't even use classes
 when I don't need to.


 How do you use a for loop to iterate over an associative array whose
 implementation is hidden, or a binary tree, or any arbitrary
 container, or a sequence or words in a file, or the zipped contents
 of two lists, or...

 The point of foreach isn't performance, it's flexibility and
 abstraction.  As long as you can make an opApply or function which
 takes a delegate, you can use the foreach loop with it.  Not
 everything is an array.


 Where are the docs on opApply?


 
 Search opApply in http://www.digitalmars.com/d/1.0/statement.html
 
 Can't the search in digitalmars.com/d be improved? Searching for
 "opApply" you get ten results which are just questions in the
 newsgroups, and just in the second page you can see the result you
 probably are looking for.
 
 I suggest improving it in this way:
 1. Have a map of obvious keywords that people will look for, to precise
 urls. Some examples are: delegate, function, override, virtual, class,
 struct, union, interface, pointer, op*, operator overloading,
 inheritance, final, const, invariant, etc. 2. If the search is exactly
 one of the keywords, use the map above. 3. Else, use Google Search
 Engine.
 
 The list might be big, but it can be done if the community helps, and I
 think it will improve a lot the usability of the site.
 
 Actually, the map can be [keyword -> list of urls]. For example, for
 invariant it should point the invariant attribute as well as invariant
 classes.
 
 And don't point me to
 
 http://www.wikiservice.at/wiki4d/wiki.cgi?LanguageSpecification/




KeywordIndex

 
 
 I know it exists, but people how enter the D site (and the above is not
 the D site) will use the search box. Who uses indexes these days when
 you can search and find what you want?


 
 Umm... I didn't mean to sound rude or anything. Unfortunately, when
 someone doesn't speak in its native language, he tends to sound rude.
 
 Does anyone else have problems with the search box in digitalmars.com/d
 ?


I don't think this really sounded terribly rude. I do agree that 
searching the site can be annoying when top results are always from the 
newsgroup. Maybe an option to search digitalmars/d and one to search 
digitalmars/d/archive (don't know if that could be customized).
Nov 24 2008
prev sibling parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"Ary Borenszweig" wrote

 Umm... I didn't mean to sound rude or anything. Unfortunately, when 
 someone doesn't speak in its native language, he tends to sound rude.

 Does anyone else have problems with the search box in digitalmars.com/d ?


I never use it.  Simply because I only ever go on DM to look at the spec, 
and at bugs (which have their own search box).  For the spec, it's generally 
more fruitful to click on each page, then use my browser search to find the 
item I want.  If I use the search box, it gives me a billion results from 
the newsgroups.

If the search box could be focused at specific parts of DM, I might start 
using it.  I'd split it into:

Newsgroups
D1 spec
D1 phobos
D2 spec
D2 phobos
Articles
Everything else

With checkboxes for each so I can specify combinations if I want.

And BTW, you don't sound rude ;)

-Steve
Nov 25 2008