• Michael Kiermaier <michael.kiermaier gmx.net> Jul 03 2007
• BCS <ao pathlink.com> Jul 03 2007
• Daniel919 <Daniel919 web.de> Jul 03 2007
• Michael Kiermaier <michael.kiermaier gmx.net> Jul 04 2007
• Frits van Bommel <fvbommel REMwOVExCAPSs.nl> Jul 04 2007

Michael Kiermaier <michael.kiermaier gmx.net> writes:

BCS Wrote:

 This is getting into the ambiguity between an invariant function (that is 
 part of design by contract)


Thanks, I didn't know that "invariant" can also be used for functions;

 and an invariant value (that is one form of const).
 
 I think the way that it should be done is
 
 invariant(int) y;


I tried that, but:
Test.d(6): found 'int' when expecting ')'
Test.d(6): statement expected to be { }, not )
Test.d(6): found ')' instead of statement

Also, http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.l
arn&article_id=8217 claims that "invariant int" and "invariant(int)" are NOT
the same, but "invariant int" and  "final invariant(int)" are the same.

I don't know if that is true.

BCS <ao pathlink.com> writes:

Reply to Michael,

 BCS Wrote:
 
 This is getting into the ambiguity between an invariant function
 (that is part of design by contract)
 


 
 and an invariant value (that is one form of const).
 
 I think the way that it should be done is
 
 invariant(int) y;
 


 Test.d(6): found 'int' when expecting ')'
 Test.d(6): statement expected to be { }, not )
 Test.d(6): found ')' instead of statement
 Also,
 http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmar
 s.D.learn&article_id=8217 claims that "invariant int" and
 "invariant(int)" are NOT the same, but "invariant int" and  "final
 invariant(int)" are the same.
 
 I don't know if that is true.
 


Are you using dmd 2.x or 1.x?

Daniel919 <Daniel919 web.de> writes:

Are you using dmd 1.x ? The final-const-invariant thing only works on 
the experimental 2.x version. I tried your example there and it compiles 
without errors as expected.

 Also, http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.l
arn&article_id=8217 claims that "invariant int" and "invariant(int)" are NOT
the same, but "invariant int" and  "final invariant(int)" are the same.
 
 I don't know if that is true.


"invariant(int) x" this is useless and does not mean that x can't be 
changed, what someone might think at first.
Using brackets means that you can assign another instance of TYPE to the 
variable. But you can't change the data of the instance.

"invariant(int) x" means: you can assign another instance of int to x
You see, this doesn't make sense.
It's equal useless for all simple storage classes.

However, "final invariant(int) x = 1" works like "invariant int x = 1",
because final means: you can't assign another int to x

Michael Kiermaier <michael.kiermaier gmx.net> writes:

Daniel919 Wrote:

 Are you using dmd 1.x ? The final-const-invariant thing only works on 
 the experimental 2.x version. I tried your example there and it compiles 
 without errors as expected.


Well, that seems to be the problem:

My dmd command reports:
Digital Mars D Compiler v1.018

Where can I get the 2.x version? I cannot find it in the "download" section on
the Digitalmars D hompage

And what exactly is the status of 2.x? I believe I read somewhere, that D 2.0
was officially released. But now you write that it is still experimental.

 "invariant(int) x" this is useless and does not mean that x can't be 
 changed, what someone might think at first.
 Using brackets means that you can assign another instance of TYPE to the 
 variable. But you can't change the data of the instance.
 
 "invariant(int) x" means: you can assign another instance of int to x
 You see, this doesn't make sense.
 It's equal useless for all simple storage classes.
 
 However, "final invariant(int) x = 1" works like "invariant int x = 1",
 because final means: you can't assign another int to x


Thanks for the explanation!

~michael

Frits van Bommel <fvbommel REMwOVExCAPSs.nl> writes:

Michael Kiermaier wrote:
 Daniel919 Wrote:
 
 Are you using dmd 1.x ? The final-const-invariant thing only works on 
 the experimental 2.x version. I tried your example there and it compiles 
 without errors as expected.


 Well, that seems to be the problem:
 
 My dmd command reports:
 Digital Mars D Compiler v1.018
 
 Where can I get the 2.x version? I cannot find it in the "download" section on
the Digitalmars D hompage


It's on the changelog page: http://www.digitalmars.com/d/changelog.html
Be sure to click the 2.002 link, the "latest version" link seems to be 
out of date (points to 2.001).

 And what exactly is the status of 2.x? I believe I read somewhere, that D 2.0
was officially released. But now you write that it is still experimental.


It's an experimental alpha version. That means it's got the latest 
additions, but may be more buggy and later versions can change and break 
code that used to work.