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digitalmars.D - why no statements inside mixin teplates?

reply =?UTF-8?B?2LPZhNmK2YXYp9mGINin2YTYs9mH?= writes:
Is there a rational behind not allowing statements inside mixin 
templates? I know mixin does accept code containing statements, 
but using mixin is much uglier. so  I was wondering.

example use case:
//---------------------------------
int compute(string)
{
     return 1;
}

mixin template testBoilerPlate(alias arg, alias expected)
{
     {
         import std.format : format;
         auto got = compute(arg);
         assert(got == expected, "expected %s got 
%s".format(expected, got));
     }
}

unittest
{
     mixin testBoilerPlate("12345", 1);
     mixin testBoilerPlate("00" ~ "0", 2 - 1);
}
//--------------------------------
May 11 2017
next sibling parent reply visitor <visitor gmail.com> writes:
On Friday, 12 May 2017 at 00:20:13 UTC, سليمان السهمي (Soulaïman 
Sahmi) wrote:

 Is there a rational behind not allowing statements inside mixin 
 templates? I know mixin does accept code containing statements, 
 but using mixin is much uglier. so  I was wondering.

 example use case:
 //---------------------------------
 int compute(string)
 {
     return 1;
 }

 mixin template testBoilerPlate(alias arg, alias expected)
 {
     {
         import std.format : format;
         auto got = compute(arg);
         assert(got == expected, "expected %s got 
 %s".format(expected, got));
     }
 }

 unittest
 {
     mixin testBoilerPlate("12345", 1);
     mixin testBoilerPlate("00" ~ "0", 2 - 1);
 }
 //--------------------------------


On Friday, 12 May 2017 at 00:20:13 UTC, سليمان السهمي (Soulaïman 
Sahmi) wrote:

works for me :
mixin template testBoilerPlate(alias arg, alias expected)
{
     auto doit = {
         import std.format : format;
         auto got = compute(arg);
         assert(got == expected, "expected %s got 
%s".format(expected, got));
         return true;
     }();
}
May 12 2017
next sibling parent reply Andrea Fontana <nospam example.com> writes:
On Friday, 12 May 2017 at 08:47:32 UTC, visitor wrote:

 works for me :
 mixin template testBoilerPlate(alias arg, alias expected)
 {
     auto doit = {
         import std.format : format;
         auto got = compute(arg);
         assert(got == expected, "expected %s got 
 %s".format(expected, got));
         return true;
     }();
 }


Another error: you want to invoke mixin with 
testBoilerPlate!(...) not testBoilerPlate();
May 12 2017
parent visitor <visitor gmail.com> writes:
On Friday, 12 May 2017 at 09:02:25 UTC, Andrea Fontana wrote:

 Another error: you want to invoke mixin with 
 testBoilerPlate!(...) not testBoilerPlate();


yes, forgot to add it ...
May 12 2017
prev sibling parent =?UTF-8?B?2LPZhNmK2YXYp9mGINin2YTYs9mH?= writes:
On Friday, 12 May 2017 at 08:47:32 UTC, visitor wrote:

 works for me :
 mixin template testBoilerPlate(alias arg, alias expected)
 {
     auto doit = {
         import std.format : format;
         auto got = compute(arg);
         assert(got == expected, "expected %s got 
 %s".format(expected, got));
         return true;
     }();
 }


nice hack, or should I say idiom? I definitely didn't think of 
that one, I though of  using a parameterized function which kinda 
similar. but this isn't what I'm looking for.I just want to do C 
style macro expansion. no function/lambda call at runtime, even 
if the optimizer inlines the lambda's. I can do this with plain 
mixin, but it's uglier.

example with mixin:
//-----------------------
string testBoilerPlate(alias arg, alias expected)()
{
     import std.format : format;

     return q{
         {
             import std.format : format;
             auto got = compute(%1$s);
             assert(%2$s == got, "expected %%s, got 
%%s".format(%2$s, got));
         }
     }.format(arg.stringof, expected.stringof);
}

unittest
{
     mixin(testBoilerPate!("000", 1));
}
//-----------------------
May 12 2017
prev sibling next sibling parent reply =?UTF-8?B?2LPZhNmK2YXYp9mGINin2YTYs9mH?= writes:
On Friday, 12 May 2017 at 00:20:13 UTC, سليمان السهمي (Soulaïman 
Sahmi) wrote:

 Is there a rational behind not allowing statements inside mixin 
 templates? ...


I guess the answer is, nobody has written a DIP for it?
May 12 2017
parent Domain <dont_email empty.com> writes:
On Friday, 12 May 2017 at 20:51:17 UTC, سليمان السهمي (Soulaïman 
Sahmi) wrote:

 On Friday, 12 May 2017 at 00:20:13 UTC, سليمان السهمي 
 (Soulaïman Sahmi) wrote:

 Is there a rational behind not allowing statements inside 
 mixin templates? ...


 I guess the answer is, nobody has written a DIP for it?


I am also wondering why, this is a very useful feature. Now I 
have to use string mixin hack.
Jul 27 2017
prev sibling parent John Colvin <john.loughran.colvin gmail.com> writes:
On Friday, 12 May 2017 at 00:20:13 UTC, سليمان السهمي (Soulaïman 
Sahmi) wrote:

 Is there a rational behind not allowing statements inside mixin 
 templates? I know mixin does accept code containing statements, 
 but using mixin is much uglier. so  I was wondering.

 example use case:
 //---------------------------------
 int compute(string)
 {
     return 1;
 }

 mixin template testBoilerPlate(alias arg, alias expected)
 {
     {
         import std.format : format;
         auto got = compute(arg);
         assert(got == expected, "expected %s got 
 %s".format(expected, got));
     }
 }

 unittest
 {
     mixin testBoilerPlate("12345", 1);
     mixin testBoilerPlate("00" ~ "0", 2 - 1);
 }
 //--------------------------------


If you can put up with the limitation of what can be done in a 
nested function then this convention works (choose whatever names 
you want, A and __ are just for example):

mixin template A()
{
	auto __()
	{
		++a;
	}
}

void main()
{
	int a = 0;

	mixin A!() __; __.__;

	assert (a == 1);
}
Jul 27 2017