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digitalmars.D.learn - Reason for 'static struct'

reply Jon D <jond noreply.com> writes:
There is a fair bit of range related code in the standard library 
structured like:

     auto MyRange(Range)(Range r)
         if (isInputRange!Range)
      {
         static struct Result
         {
             private Range source;
             // define empty, front, popFront, etc
         }
         return Result(r);
     }

I'm curious about what declaring the Result struct as 'static' 
does, and if there are use cases where it be better to exclude 
the static qualifier.

--Jon
Dec 09 2015
parent reply Daniel =?UTF-8?B?S296w6Fr?= via Digitalmars-d-learn writes:
V Wed, 09 Dec 2015 21:10:43 +0000
Jon D via Digitalmars-d-learn <digitalmars-d-learn puremagic.com>
napsáno:


 There is a fair bit of range related code in the standard library 
 structured like:
 
      auto MyRange(Range)(Range r)
          if (isInputRange!Range)
       {
          static struct Result
          {
              private Range source;
              // define empty, front, popFront, etc
          }
          return Result(r);
      }
 
 I'm curious about what declaring the Result struct as 'static' 
 does, and if there are use cases where it be better to exclude 
 the static qualifier.
 
 --Jon


It make it non-nested struct: https://dlang.org/spec/struct.html#nested
Dec 09 2015
parent reply Jon D <jond noreply.com> writes:
On Wednesday, 9 December 2015 at 21:23:03 UTC, Daniel Kozák wrote:

 V Wed, 09 Dec 2015 21:10:43 +0000
 Jon D via Digitalmars-d-learn 
 <digitalmars-d-learn puremagic.com>
 napsáno:


 There is a fair bit of range related code in the standard 
 library structured like:
 
      auto MyRange(Range)(Range r)
          if (isInputRange!Range)
       {
          static struct Result
          {
              private Range source;
              // define empty, front, popFront, etc
          }
          return Result(r);
      }
 
 I'm curious about what declaring the Result struct as 'static' 
 does, and if there are use cases where it be better to exclude 
 the static qualifier.
 
 --Jon


 It make it non-nested struct: 
 https://dlang.org/spec/struct.html#nested


Thanks. So, is in the example above, would the advantage be that 
'static' avoids saving the enclosing state, which is not needed?
Dec 09 2015
parent Daniel Kozak via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> writes:
Yes, exactly. Some people even use static if it is not needed because it is
harmless. And remove it only when enclosing context is demand.
Dne 9. 12. 2015 22:40 napsal u=C5=BEivatel "Jon D via Digitalmars-d-learn" =
<
digitalmars-d-learn puremagic.com>:


 On Wednesday, 9 December 2015 at 21:23:03 UTC, Daniel Koz=C3=A1k wrote:


 V Wed, 09 Dec 2015 21:10:43 +0000
 Jon D via Digitalmars-d-learn <digitalmars-d-learn puremagic.com>
 naps=C3=A1no:

 There is a fair bit of range related code in the standard library

 structured like:

      auto MyRange(Range)(Range r)
          if (isInputRange!Range)
       {
          static struct Result
          {
              private Range source;
              // define empty, front, popFront, etc
          }
          return Result(r);
      }

 I'm curious about what declaring the Result struct as 'static' does, an=






d

 if there are use cases where it be better to exclude the static qualifi=






er.

 --Jon


 It make it non-nested struct: https://dlang.org/spec/struct.html#nested


 Thanks. So, is in the example above, would the advantage be that 'static'
 avoids saving the enclosing state, which is not needed?
Dec 10 2015