• Hxal <hxal freenode.d.channel> Dec 12 2007
• Gilles G. <schaouette free.fr> Dec 12 2007
• Hxal <hxal freenode.d.channel> Dec 12 2007
• Oskar Linde <oskar.lindeREM OVEgmail.com> Dec 13 2007
• Sean Kelly <sean f4.ca> Dec 13 2007

Hxal <hxal freenode.d.channel> writes:

Don Clugston Wrote:

 pure real pi = 3.141592564;
 ...
 pure int foo(int a, int b);


Greetings fellow D community members. (since this is my first post.)

I'm not terribly fond of either the enum or the pure idea.

Perhaps this discussion is the perfect opportunity to revise the use of alias
declarations. Suppose we changed the alias syntax to the form of "alias x = y;"
We could amend its semantics to allow aliasing of values which would give us
what this discussions seems to be about - named values taking no memory space.

If we wanted to be able to specify the type we could further change the syntax
to either "alias optionaltype x = y;" or "optionaltype alias x = y;".

As far as pure functions go I guess the new alias could enable declaring a named
function literal: "alias foo = function int(int a, int b) {...};";
however I'd like to turn the attention of the community to the nifty pragma
statement, which I find underused. Pragmas can be an excellent way to provide
hints to the compiler without introducing new syntax, ie:
pragma (pure, functionname);
pragma (inline, functionname);
or even pragma (pure); inside the function body.

PS. My fondness of pragmas comes from my Ada programming background.

Gilles G. <schaouette free.fr> writes:

"alias" does not express the intent of the definition.
For example, when writing "alias foo = function int(int a, int b) {...};", the
fact that the function does not have side effects is not explicit.
The expressions
pure real pi=3.14159;
pure real A = area(real diameter);
are much more informative.

Hxal Wrote:

 Don Clugston Wrote:
 
 pure real pi = 3.141592564;
 ...
 pure int foo(int a, int b);


 Greetings fellow D community members. (since this is my first post.)
 
 I'm not terribly fond of either the enum or the pure idea.
 
 Perhaps this discussion is the perfect opportunity to revise the use of alias
 declarations. Suppose we changed the alias syntax to the form of "alias x = y;"
 We could amend its semantics to allow aliasing of values which would give us
 what this discussions seems to be about - named values taking no memory space.
 
 If we wanted to be able to specify the type we could further change the syntax
 to either "alias optionaltype x = y;" or "optionaltype alias x = y;".
 
 As far as pure functions go I guess the new alias could enable declaring a
named
 function literal: "alias foo = function int(int a, int b) {...};";
 however I'd like to turn the attention of the community to the nifty pragma
 statement, which I find underused. Pragmas can be an excellent way to provide
 hints to the compiler without introducing new syntax, ie:
 pragma (pure, functionname);
 pragma (inline, functionname);
 or even pragma (pure); inside the function body.
 
 PS. My fondness of pragmas comes from my Ada programming background.
 

Hxal <hxal freenode.d.channel> writes:

Gilles G. Wrote:

 "alias" does not express the intent of the definition.
 For example, when writing "alias foo = function int(int a, int b) {...};", the
fact that the function does not have side effects is not explicit.
 The expressions
 pure real pi=3.14159;
 pure real A = area(real diameter);
 are much more informative.


You're right, this one doesn't. A pure pragma suits function definitions a lot
better though. I realized after I wrote the first suggestion that you can even
write "pragma(pure) int foo (...) {}".

As for using an alias declaration for constants, it's no less informative than
a pure constant declaration, except it doesn't introduce a new keyword, nor
does it reuse an existing one in a non-obvious way (enum).

Oskar Linde <oskar.lindeREM OVEgmail.com> writes:

Hxal wrote:
 Don Clugston Wrote:
 
 pure real pi = 3.141592564;
 ...
 pure int foo(int a, int b);




I don't think pure is the optimal solution, but it is much better than 
enum and I could definitely live with it.

 Greetings fellow D community members. (since this is my first post.)
 
 I'm not terribly fond of either the enum or the pure idea.
 
 Perhaps this discussion is the perfect opportunity to revise the use of alias
 declarations. Suppose we changed the alias syntax to the form of "alias x = y;"
 We could amend its semantics to allow aliasing of values which would give us
 what this discussions seems to be about - named values taking no memory space.
 
 If we wanted to be able to specify the type we could further change the syntax
 to either "alias optionaltype x = y;" or "optionaltype alias x = y;".


I agree.

It feels like lately, the design of D has left that of the free 
outside-the-box thinker and attained a C++ mindset where simplicity and 
elegance is rendered irrelevant. I hope I am wrong. :)

-- 
Oskar

Sean Kelly <sean f4.ca> writes:

Oskar Linde wrote:
 
 It feels like lately, the design of D has left that of the free 
 outside-the-box thinker and attained a C++ mindset where simplicity and 
 elegance is rendered irrelevant. I hope I am wrong. :)


I think this is inevitable as the popularity of a language increases and 
breaking changes becomes less and less appealing.  But I am hoping we 
can hold that day off as long as possible.  Still the presence of things 
like foreach_reverse suggest that it may already be here ;-)


Sean