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digitalmars.D.learn - random access-range without lower-power range kinds?

reply spir <denis.spir gmail.com> writes:
Hello,

It seems impossible to define a random-access range (opIndex + length) alon=
e. In fact, I cannot have it used by the language. Am I missing something?
Random-access looks enough to provide fonctionality for both input and bidi=
rectional ranges without any additional method. "Lowering" for forward iter=
ation means I guess ;-)
	for (uint i=3D0 ; i < coll.length ; i++) {
	    element =3D coll[i];
	    doSomethingWith(element);
	}
What is the reason for requiring methods of lower-power range types to be d=
efined? (This makes 5 methods!)

Denis
-- -- -- -- -- -- --
vit esse estrany =E2=98=A3

spir.wikidot.com
Dec 14 2010
next sibling parent reply "Lars T. Kyllingstad" <public kyllingen.NOSPAMnet> writes:
On Tue, 14 Dec 2010 09:09:33 +0100, spir wrote:

 Hello,
 
 It seems impossible to define a random-access range (opIndex + length)
 alone. In fact, I cannot have it used by the language. Am I missing
 something? Random-access looks enough to provide fonctionality for both
 input and bidirectional ranges without any additional method. "Lowering"
 for forward iteration means I guess ;-)
 	for (uint i=0 ; i < coll.length ; i++) {
 	    element = coll[i];
 	    doSomethingWith(element);
 	}
 What is the reason for requiring methods of lower-power range types to
 be defined? (This makes 5 methods!)
 
 Denis
 -- -- -- -- -- -- --
 vit esse estrany ☣
 
 spir.wikidot.com

To avoid the boilerplate, you could write a mixin that defines the iteration primitives for you. mixin template IterationFuncs() { int index; bool empty() { return index == length; } auto front() { return opIndex(index); } void popFront() { ++index; } // ... etc. } Then you'd just have to define opIndex() and length(), and the mixin does the rest for you. struct MyRange(T) { T opIndex(int i) { ... } property int length() { ... } mixin IterationFuncs!(); } (I haven't tested the code above, so it probably has bugs, but you get the point.) -Lars
Dec 14 2010
parent Jesse Phillips <jessekphillips+D gmail.com> writes:
Lars T. Kyllingstad Wrote:

 To avoid the boilerplate, you could write a mixin that defines the 
 iteration primitives for you.
 
   mixin template IterationFuncs()
   {
       int index;
       bool empty() { return index == length; }
       auto front() { return opIndex(index); }
       void popFront() { ++index; }
       // ... etc.
   }
 
 Then you'd just have to define opIndex() and length(), and the mixin does 
 the rest for you.
 
   struct MyRange(T)
   {
       T opIndex(int i) { ... }
        property int length() { ... }
       mixin IterationFuncs!();
   }
 
 (I haven't tested the code above, so it probably has bugs, but you get 
 the point.)
 
 -Lars

Maybe this should be added to std.range? http://d.puremagic.com/issues/show_bug.cgi?id=5351
Dec 14 2010
prev sibling parent spir <denis.spir gmail.com> writes:
On Tue, 14 Dec 2010 14:15:20 +0000 (UTC)
"Lars T. Kyllingstad" <public kyllingen.NOSPAMnet> wrote:

 On Tue, 14 Dec 2010 09:09:33 +0100, spir wrote:
=20
 Hello,
=20
 It seems impossible to define a random-access range (opIndex + length)
 alone. In fact, I cannot have it used by the language. Am I missing
 something? Random-access looks enough to provide fonctionality for both
 input and bidirectional ranges without any additional method. "Lowering"
 for forward iteration means I guess ;-)
 	for (uint i=3D0 ; i < coll.length ; i++) {
 	    element =3D coll[i];
 	    doSomethingWith(element);
 	}
 What is the reason for requiring methods of lower-power range types to
 be defined? (This makes 5 methods!)
=20
 Denis
 -- -- -- -- -- -- --
 vit esse estrany =E2=98=A3
=20
 spir.wikidot.com

=20 To avoid the boilerplate, you could write a mixin that defines the=20 iteration primitives for you. =20 mixin template IterationFuncs() { int index; bool empty() { return index =3D=3D length; } auto front() { return opIndex(index); } void popFront() { ++index; } // ... etc. } =20 Then you'd just have to define opIndex() and length(), and the mixin does=

 the rest for you.
=20
   struct MyRange(T)
   {
       T opIndex(int i) { ... }
        property int length() { ... }
       mixin IterationFuncs!();
   }
=20
 (I haven't tested the code above, so it probably has bugs, but you get=20
 the point.)
=20
 -Lars

Thank you, Lars. Nice method! Denis -- -- -- -- -- -- -- vit esse estrany =E2=98=A3 spir.wikidot.com
Dec 14 2010