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D - Slice notation - slicing to end, or from start

reply "Matthew Wilson" <matthew stlsoft.org> writes:
Is there any chance we could amend the slice notation such that

  ar[2 .. ]   would be interpreted as ar[2 .. ar.length]
  ar[ .. 10]   would be interpreted as ar[0 .. 10]
  ar[ .. ]   would be interpreted as ar[0 .. ar.length]

(The last one would be pretty useless, of course).

It's just syntactic sugar, I grant you, but it would be nice nonetheless. If
there's no serious parsing issue, can we add this to the list of nice
features.

Of course, the form t[1 .. ] might cause some problems with the overloaded
slice operator for UDTs, ...
Oct 10 2003
next sibling parent reply "Daniel Yokomiso" <daniel_yokomiso yahoo.com.br> writes:
"Matthew Wilson" <matthew stlsoft.org> escreveu na mensagem
news:bm836b$2pr4$1 digitaldaemon.com...
 Is there any chance we could amend the slice notation such that

   ar[2 .. ]   would be interpreted as ar[2 .. ar.length]
   ar[ .. 10]   would be interpreted as ar[0 .. 10]
   ar[ .. ]   would be interpreted as ar[0 .. ar.length]

 (The last one would be pretty useless, of course).

 It's just syntactic sugar, I grant you, but it would be nice nonetheless.

 there's no serious parsing issue, can we add this to the list of nice
 features.

 Of course, the form t[1 .. ] might cause some problems with the overloaded
 slice operator for UDTs, ...

In Haskell they have a Enum type-class and the .. operator is a syntatic sugar for certain operations, so they can write: [1 .. 10] -> enumFromTo 1 10 [1 .. ] -> enumFrom 1 [1, 3 .. 9] -> enumFromThenTo 1 3 9 [1, 3 .. ] -> enumFromThen 1 3 The "then" part is used to define steps. Anyway I think in D we could do similar things and have the .. operator create a templated Range construct: 1 .. 10 -> new instance TRange(int).FromTo(1,10) 1 .. -> new instance TRange(int).From(1) .. 10 -> new instance TRange(int).To(10) and the array semantics would use this range definitions to know which indices it should iterate. So there are three possibilities: FromTo -> use the range bounds From -> use the range "from" bound and the array.length as upper bound To -> use the range "to" bound and 0 as lower bound The nice thing about this notation is that someone can create a UDT that uses this notation, if it provides a pair of "successor"/"predecessor" methods (or succ/pred if you want to be economic ;) for the UDT. struct MyValue { int x; MyValue succ() { return {x + 1}; } MyValue pred() { return {x - 1}; } } MyValue a = {1}; MyValue b = {2}; for(MyValue c; a .. b) { printf("%d\r\n", c.x); } The possibilities are endless, but I digress... Best regards, Daniel Yokomiso. "I'll take the red pill, no, blue. AAAHHHHHHHHHHHHHHHH........" - The Matrix meets Monty Python's Holy Grail. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.524 / Virus Database: 321 - Release Date: 8/10/2003
Oct 11 2003
parent "Matthew Wilson" <matthew stlsoft.org> writes:
Sounds interesting. I think this would be worth exploring, when Walter has
the time.

"Daniel Yokomiso" <daniel_yokomiso yahoo.com.br> wrote in message
news:bm9vh6$29u9$1 digitaldaemon.com...
 "Matthew Wilson" <matthew stlsoft.org> escreveu na mensagem
 news:bm836b$2pr4$1 digitaldaemon.com...
 Is there any chance we could amend the slice notation such that

   ar[2 .. ]   would be interpreted as ar[2 .. ar.length]
   ar[ .. 10]   would be interpreted as ar[0 .. 10]
   ar[ .. ]   would be interpreted as ar[0 .. ar.length]

 (The last one would be pretty useless, of course).

 It's just syntactic sugar, I grant you, but it would be nice


 If
 there's no serious parsing issue, can we add this to the list of nice
 features.

 Of course, the form t[1 .. ] might cause some problems with the


 slice operator for UDTs, ...

In Haskell they have a Enum type-class and the .. operator is a syntatic sugar for certain operations, so they can write: [1 .. 10] -> enumFromTo 1 10 [1 .. ] -> enumFrom 1 [1, 3 .. 9] -> enumFromThenTo 1 3 9 [1, 3 .. ] -> enumFromThen 1 3 The "then" part is used to define steps. Anyway I think in D we could do similar things and have the .. operator create a templated Range

 1 .. 10    ->   new instance TRange(int).FromTo(1,10)
 1 ..       ->   new instance TRange(int).From(1)
   .. 10    ->   new instance TRange(int).To(10)


 and the array semantics would use this range definitions to know which
 indices it should iterate. So there are three possibilities:


 FromTo  -> use the range bounds
 From    -> use the range "from" bound and the array.length as upper bound
 To      -> use the range "to" bound and 0 as lower bound


 The nice thing about this notation is that someone can create a UDT that
 uses this notation, if it provides a pair of "successor"/"predecessor"
 methods (or succ/pred if you want to be economic ;) for the UDT.

 struct MyValue {
     int x;
     MyValue succ() {
         return {x + 1};
     }
     MyValue pred() {
         return {x - 1};
     }
 }

 MyValue a = {1};
 MyValue b = {2};

 for(MyValue c; a .. b) {
     printf("%d\r\n", c.x);
 }


 The possibilities are endless, but I digress...

 Best regards,
 Daniel Yokomiso.

 "I'll take the red pill, no, blue. AAAHHHHHHHHHHHHHHHH........"
  - The Matrix meets Monty Python's Holy Grail.


 ---
 Outgoing mail is certified Virus Free.
 Checked by AVG anti-virus system (http://www.grisoft.com).
 Version: 6.0.524 / Virus Database: 321 - Release Date: 8/10/2003

Oct 11 2003
prev sibling next sibling parent "Ben Hinkle" <bhinkle4 juno.com> writes:
MATLAB uses the keyword "end" for this. Some example translated to D array
syntax:
 ar[2 .. end] = 0;
 ar[2 .. end-1] = 0;
 ar[end+1] = 0;

The last example grows the array by one element and sets it to zero.

Since slicing in MATLAB is inclusive "end" would evaluate to ar.length+1.

-Ben

"Matthew Wilson" <matthew stlsoft.org> wrote in message
news:bm836b$2pr4$1 digitaldaemon.com...
 Is there any chance we could amend the slice notation such that

   ar[2 .. ]   would be interpreted as ar[2 .. ar.length]
   ar[ .. 10]   would be interpreted as ar[0 .. 10]
   ar[ .. ]   would be interpreted as ar[0 .. ar.length]

 (The last one would be pretty useless, of course).

 It's just syntactic sugar, I grant you, but it would be nice nonetheless.

 there's no serious parsing issue, can we add this to the list of nice
 features.

 Of course, the form t[1 .. ] might cause some problems with the overloaded
 slice operator for UDTs, ...

Oct 12 2003
prev sibling parent "Carlos Santander B." <carlos8294 msn.com> writes:
"Matthew Wilson" <matthew stlsoft.org> wrote in message
news:bm836b$2pr4$1 digitaldaemon.com...
| Is there any chance we could amend the slice notation such that
|
|   ar[2 .. ]   would be interpreted as ar[2 .. ar.length]
|   ar[ .. 10]   would be interpreted as ar[0 .. 10]
|   ar[ .. ]   would be interpreted as ar[0 .. ar.length]
|
| (The last one would be pretty useless, of course).
|
| It's just syntactic sugar, I grant you, but it would be nice nonetheless.
If
| there's no serious parsing issue, can we add this to the list of nice
| features.
|
| Of course, the form t[1 .. ] might cause some problems with the overloaded
| slice operator for UDTs, ...
|
|
|
|

I second this.

覧覧覧覧覧覧覧覧覧覧覧覧
Carlos Santander


---

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Version: 6.0.525 / Virus Database: 322 - Release Date: 2003-10-09
Oct 12 2003