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digitalmars.D.learn - mixin template FAIL

reply Zach the Mystic <reachzachatgooglesmailservice dot.com> writes:
I decided to try using template mixin, but even the simplest program 
fails. What's wrong with this code? Error list follows.
DMD64 D Compiler v2.057  OSX 10.6

import std.stdio;

mixin template helpMe()
{
    writeln("Satisfying!");
}

void main()
{
    mixin helpMe();
}

test.d(5): unexpected ( in declarator
test.d(5): basic type expected, not "Satisfying!"
test.d(5): found '"Satisfying!"' when expecting ')'
test.d(5): no identifier for declarator writeln(int)
test.d(5): semicolon expected following function declaration
test.d(5): Declaration expected, not ')'
test.d(10): ';' expected after mixin
test.d(10): found ')' instead of statement
Feb 21 2012
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 02/21/2012 10:47 AM, Zach the Mystic wrote:

 I decided to try using template mixin, but even the simplest program
 fails. What's wrong with this code? Error list follows.
 DMD64 D Compiler v2.057 OSX 10.6

 import std.stdio;

 mixin template helpMe()
 {
 writeln("Satisfying!");
 }

 void main()
 {
 mixin helpMe();
 }

 test.d(5): unexpected ( in declarator
 test.d(5): basic type expected, not "Satisfying!"
 test.d(5): found '"Satisfying!"' when expecting ')'
 test.d(5): no identifier for declarator writeln(int)
 test.d(5): semicolon expected following function declaration
 test.d(5): Declaration expected, not ')'
 test.d(10): ';' expected after mixin
 test.d(10): found ')' instead of statement


According to the docs, template mixins can have only declarations but 
helpMe above has a statement.

   http://dlang.org/template-mixin.html

Ali
Feb 21 2012
next sibling parent Jacob Carlborg <doob me.com> writes:
On 2012-02-21 20:53, Ali Çehreli wrote:

 On 02/21/2012 10:47 AM, Zach the Mystic wrote:
  > I decided to try using template mixin, but even the simplest program
  > fails. What's wrong with this code? Error list follows.
  > DMD64 D Compiler v2.057 OSX 10.6
  >
  > import std.stdio;
  >
  > mixin template helpMe()
  > {
  > writeln("Satisfying!");
  > }
  >
  > void main()
  > {
  > mixin helpMe();
  > }
  >
  > test.d(5): unexpected ( in declarator
  > test.d(5): basic type expected, not "Satisfying!"
  > test.d(5): found '"Satisfying!"' when expecting ')'
  > test.d(5): no identifier for declarator writeln(int)
  > test.d(5): semicolon expected following function declaration
  > test.d(5): Declaration expected, not ')'
  > test.d(10): ';' expected after mixin
  > test.d(10): found ')' instead of statement
  >

 According to the docs, template mixins can have only declarations but
 helpMe above has a statement.

 http://dlang.org/template-mixin.html

 Ali


And the correct syntax for mixing in the template would be:

mixin helpMe!();

Or

mixin helpMe; // works if the template doesn't take any arguments

-- 
/Jacob Carlborg
Feb 21 2012
prev sibling next sibling parent Ellery Newcomer <ellery-newcomer utulsa.edu> writes:
On 02/21/2012 01:53 PM, Ali Çehreli wrote:

 According to the docs, template mixins can have only declarations but
 helpMe above has a statement.

 http://dlang.org/template-mixin.html

 Ali


come to think of it, I've occasionally wished for statement mixins. This 
would make a good enhancement request.
Feb 21 2012
prev sibling parent reply Zach the Mystic <reachzachatgooglesmailservice dot.com> writes:
On 2/21/12 2:53 PM, Ali Çehreli wrote:

 According to the docs, template mixins can have only declarations but
 helpMe above has a statement.

 http://dlang.org/template-mixin.html

 Ali


Thanks for your reply. You're right about the statement. But I still 
think something's wrong. For example, even this program produces the errors:

import std.stdio;

mixin template helpMe()
{
    writeln("Satisfying!");
}

void main(){}

test.d(5): unexpected ( in declarator
test.d(5): basic type expected, not "Satisfying!"
test.d(5): found '"Satisfying!"' when expecting ')'
test.d(5): no identifier for declarator writeln(int)
test.d(5): semicolon expected following function declaration
test.d(5): Declaration expected, not ')'

The parser just isn't recognizing the presence of the template mixin 
format. The errors happen instantly, which generally happens only when 
you have parser errors. I don't know, but I think there might be some 
stupid typo in the source code for the current dmd I'm using (2.057 Mac 
OSX 10.6). I'd have to download another version, but I was distracted by 
other things.

Zach
Feb 23 2012
next sibling parent "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Thu, Feb 23, 2012 at 05:27:03PM -0500, Zach the Mystic wrote:

 On 2/21/12 2:53 PM, Ali Çehreli wrote:

According to the docs, template mixins can have only declarations but
helpMe above has a statement.

http://dlang.org/template-mixin.html

Ali


 
 Thanks for your reply. You're right about the statement. But I still
 think something's wrong. For example, even this program produces the
 errors:
 
 import std.stdio;
 
 mixin template helpMe()
 {
    writeln("Satisfying!");


The writeln call is a statement.

I think what you want is this:

	template helpMe() {
		mixin(`writeln("Satisfying!");`);
	}


T

-- 
Real Programmers use "cat > a.out".
Feb 23 2012
prev sibling parent reply Ellery Newcomer <ellery-newcomer utulsa.edu> writes:
 Thanks for your reply. You're right about the statement. But I still
 think something's wrong. For example, even this program produces the
 errors:

 import std.stdio;

 mixin template helpMe()
 {
 writeln("Satisfying!");
 }


does it do that if you replace the statement with a declaration?

like this:

mixin template helpMe()
{
   int durrr = (writeln("Satisfying!"), 1);
}
Feb 23 2012
parent reply Zach the Mystic <reachzachatgooglesmailservice dot.com> writes:
On 2/23/12 7:33 PM, Ellery Newcomer wrote:

 import std.stdio;

 mixin template helpMe()
 {
 writeln("Satisfying!");
 }


 does it do that if you replace the statement with a declaration?

 like this:

 mixin template helpMe()
 {
 int durrr = (writeln("Satisfying!"), 1);
 }


No, it doesn't. You're right. I guess I have a long way to go to learn 
these things.

Thank you. Even at my primitive level, though, I can see how awesome 
these things could be once you know how to program them. Does any other 
language come close to D in terms of generics? I don't know, I'm just 
asking?

Zach
Feb 24 2012
next sibling parent "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Fri, Feb 24, 2012 at 03:08:18PM -0500, Zach the Mystic wrote:
[...]

 Does any other language come close to D in terms of generics? I don't
 know, I'm just asking?


[...]

AFAIK, no. But then I only have C++ to compare with, and if I understand

templates (in terms of expressive power, though they are certainly a lot
cleaner than the mess that is C++ template syntax).


T

-- 
Some ideas are so stupid that only intellectuals could believe them. -- George
Orwell
Feb 24 2012
prev sibling parent James Miller <james aatch.net> writes:
On Feb 25, 2012 9:08 AM, "Zach the Mystic" <
reachzachatgooglesmailservice dot.com> wrote:

 On 2/23/12 7:33 PM, Ellery Newcomer wrote:

 import std.stdio;

 mixin template helpMe()
 {
 writeln("Satisfying!");
 }


 does it do that if you replace the statement with a declaration?

 like this:

 mixin template helpMe()
 {
 int durrr = (writeln("Satisfying!"), 1);
 }



 No, it doesn't. You're right. I guess I have a long way to go to learn


these things.

 Thank you. Even at my primitive level, though, I can see how awesome


these things could be once you know how to program them. Does any other
language come close to D in terms of generics? I don't know, I'm just
asking?

 Zach


Lisp macros. But that's not a fair comparison, Lisp's object system was
built using their macros...

--
James Miller
Feb 24 2012