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digitalmars.D.learn - Compiler errors and recursive nested functions

reply "Dylan Knutson" <tcdknutson gmail.com> writes:
Hello! I'm trying to make a deepMap function which operates on 
the deepest non-range element of an array. I think that this 
function should theoretically work, however there are some 
compiler errors that I can't quite understand.

Here's the code: http://dpaste.dzfl.pl/97918311

And the compiler error because DPaste's compiler service seems to 
be offline:

src\algorithm_util.d(26): Error: function 
algorithm_util.__unittestL34_5.deepMap!(__lambda4, int[]).deepMap 
is a nested function and cannot be accessed from 
algorithm_util.__unittestL34_5.deepMap!(__lambda4, 
int[][]).deepMap.__lambda2300!(int[]).__lambda2300DMD
v2.064 DEBUG

deepMap works just fine if I pass in an array that isn't nested, 
so this will work:

	auto a = [1, 2, 3];
	auto b = a.deepMap!(a => a + 1)();
	writeln(b);
	// "[2, 3, 4]"

Can someone explain what is going on?

Thank you,
Dylan Knutson
Jun 12 2013
next sibling parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 06/12/2013 03:45 PM, Dylan Knutson wrote:

 Hello! I'm trying to make a deepMap function which operates on the
 deepest non-range element of an array. I think that this function should
 theoretically work, however there are some compiler errors that I can't
 quite understand.

 Here's the code: http://dpaste.dzfl.pl/97918311

 And the compiler error because DPaste's compiler service seems to be
 offline:

 src\algorithm_util.d(26): Error: function
 algorithm_util.__unittestL34_5.deepMap!(__lambda4, int[]).deepMap is a
 nested function and cannot be accessed from
 algorithm_util.__unittestL34_5.deepMap!(__lambda4,
 int[][]).deepMap.__lambda2300!(int[]).__lambda2300DMD
 v2.064 DEBUG

 deepMap works just fine if I pass in an array that isn't nested, so this
 will work:

      auto a = [1, 2, 3];
      auto b = a.deepMap!(a => a + 1)();
      writeln(b);
      // "[2, 3, 4]"

 Can someone explain what is going on?

 Thank you,
 Dylan Knutson


Perhaps this limitation:

   http://d.puremagic.com/issues/show_bug.cgi?id=5710

Ali
Jun 12 2013
prev sibling parent reply "Dylan Knutson" <tcdknutson gmail.com> writes:
DPaste has stopped responding to requests at the time of writing, 
so here's the code in case its still down by the time someone 
reads this:


----
import std.algorithm : map;
import std.range : isInputRange, ElementType;

// Doesn't work
//template deepMap(alias pred, Range)
//if(isInputRange!Range)
//{
//	static if(isInputRange!(ElementType!Range))
//	{
//		alias deepMap = map!(a => deepMap!(pred, typeof(a))(a));
//	}
//	else
//	{
//		alias deepMap = map!(pred);
//	}
//}

// Neither does this, for the same reason
auto deepMap(alias pred, Range)(Range r)
if(isInputRange!Range)
{
	static if(isInputRange!(ElementType!Range))
	{
		return r.map!( a => a.deepMap!(pred)() )();
	}
	else
	{
		return r.map!(pred)();
	}
}

unittest {
	import std.stdio;

	auto a = [[1, 1], [1, 1]];
	auto b = a.deepMap!(a => a + 1)();
	writeln(b);
	//assert(b == [[2, 2], [2, 2]]);
}

----
Jun 12 2013
parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 06/12/2013 03:49 PM, Dylan Knutson wrote:


 DPaste has stopped responding to requests at the time of writing,


Being an old ;) old-timer I never understood the need for those sites.


 ----
 import std.algorithm : map;
 import std.range : isInputRange, ElementType;


As a workaround, make that lambda a free-standing function here:

auto intermediate(T, alias pred)(T a)
{
     return a.deepMap!(pred)();
}


 // Neither does this, for the same reason
 auto deepMap(alias pred, Range)(Range r)
 if(isInputRange!Range)
 {
      static if(isInputRange!(ElementType!Range))
      {
          return r.map!( a => a.deepMap!(pred)() )();


And use that free-standing instead:

         return r.map!(intermediate!(ElementType!Range, pred))();

Ali
Jun 12 2013