digitalmars.D.bugs - [Issue 4661] New: Array of lazy sequence
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http://d.puremagic.com/issues/show_bug.cgi?id=4661
Summary: Array of lazy sequence
Product: D
Version: D2
Platform: x86
OS/Version: Windows
Status: NEW
Keywords: rejects-valid
Severity: normal
Priority: P2
Component: Phobos
AssignedTo: nobody puremagic.com
ReportedBy: bearophile_hugs eml.cc
Problem in building an array of lazy sequences. This D2 code:
import std.algorithm: map;
void main() {
auto r1 = map!q{a+1}([1, 2, 3]);
auto r2 = map!q{a+2}([1, 2, 3]);
auto a = [r1, r2];
}
Fails, and DMD 2.048 shows:
Error: incompatible types for ((r1) ? (r2)): 'Map!(result,int[])' and
'Map!(result,int[])'
Additionally, the error message lacks a line number.
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Aug 17 2010
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=4661
David Simcha <dsimcha yahoo.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |dsimcha yahoo.com
Resolution| |INVALID
This bug is invalid because of the way template instantiation from string
lambdas works. Instantiating map with q{a + 1} produces a completely different
type than map instantiated with q{a + 2}, and therefore storing them in an
array should not be possible. Take a look at how Map and
std.functional.unaryFun() work. Also, to illustrate my point, note that the
following code works:
import std.algorithm: map;
void main() {
auto r1 = map!q{a+1}([1, 2, 3]);
auto r2 = map!q{a+1}([1, 2, 3]);
auto a = [r1, r2];
}
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Aug 17 2010
http://d.puremagic.com/issues/show_bug.cgi?id=4661
Brad Roberts <braddr puremagic.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
CC| |braddr puremagic.com
Resolution|INVALID |
---
Take a step back and rethink your analysis. This example is a straight forward
case of int[] to int[] mapping. They _should_ be compatible types. The map
function is irrelevant to the types involved. If the result of the map
functions differed, then you'd be right.
Also, the lack of a line number is a bug regardless of the validity of the
operation.
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Aug 17 2010
http://d.puremagic.com/issues/show_bug.cgi?id=4661
David Simcha <dsimcha yahoo.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords|rejects-valid |diagnostic
Summary|Array of lazy sequence |Array Literal Incompatible
| |Type Error Msg Should
| |Include Line Number
Ok, so this is a legit diagnostic bug. I'll grant you that. However, thinking
that Map!("a + 1", Range) and Map!("a + 2", Range) are the same type represents
a serious misunderstanding of template alias parameters. The binding of the
lambda function to the Map instance happens at compile time, not runtime.
Let's try a thought experiment, thinking at the C level. What would happen if
Map!"a + 2" were cast to Map!"a + 1" and front() were called?
Map!"a + 1".front() would be called. Inlined (probably) in Map!"a + 1".front()
is something like return _input.front + 1.
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Aug 17 2010
http://d.puremagic.com/issues/show_bug.cgi?id=4661 --- You're miring your logic in the implementation rather than the concept of what map is. Pretend it was implemented as: T[] map(T)(mapfunc, T[]); would we even be having this discussion? -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Aug 17 2010
http://d.puremagic.com/issues/show_bug.cgi?id=4661 No, I'm saying that since the lambda function is bound at compile time, this isn't a bug. It's an intentional design tradeoff. It **can't** be fixed unless the lambda function is bound at runtime instead, which would prevent it from being inlined, prevent implicit instantiation of the lambda function if it's a template, etc. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Aug 17 2010
http://d.puremagic.com/issues/show_bug.cgi?id=4661
Andrei Alexandrescu <andrei metalanguage.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |andrei metalanguage.com
19:58:25 PDT ---
I agree that the initial code shouldn't work. This code should:
import std.algorithm: map;
void main() {
auto r1 = map!q{a+1}([1, 2, 3]);
auto r2 = map!q{a+2}([1, 2, 3]);
auto a = array(chain(r1, r2));
}
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Aug 17 2010
http://d.puremagic.com/issues/show_bug.cgi?id=4661 Given the way templates work in D, the original code can't work, but I'd like to receive the error line number here. This problem is a good example to show the difference between a structural type system and a nominative one. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Aug 18 2010
http://d.puremagic.com/issues/show_bug.cgi?id=4661
yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |patch
CC| |yebblies gmail.com
Test case for the error message, and a similar case for associative array
initializers:
void main() {
auto a = [1, null];
auto b = [1 : 1, null : null];
}
https://github.com/D-Programming-Language/dmd/pull/99
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Jun 09 2011
http://d.puremagic.com/issues/show_bug.cgi?id=4661 *** Issue 5518 has been marked as a duplicate of this issue. *** -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jun 09 2011
http://d.puremagic.com/issues/show_bug.cgi?id=4661
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
CC| |bugzilla digitalmars.com
Resolution| |FIXED
12:50:14 PDT ---
https://github.com/D-Programming-Language/dmd/commit/86ea84f72c3b82ae034776e58a96054ab97f2138
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Jun 11 2011