digitalmars.D.bugs - [Issue 1861] New: .sort fails if opCmp takes ref param
- d-bugmail puremagic.com (62/62) Feb 22 2008 http://d.puremagic.com/issues/show_bug.cgi?id=1861
- d-bugmail puremagic.com (10/10) Feb 22 2008 http://d.puremagic.com/issues/show_bug.cgi?id=1861
- d-bugmail puremagic.com (4/4) Feb 22 2008 http://d.puremagic.com/issues/show_bug.cgi?id=1861
- d-bugmail puremagic.com (29/29) Feb 22 2008 http://d.puremagic.com/issues/show_bug.cgi?id=1861
- d-bugmail puremagic.com (62/62) Feb 05 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1861
http://d.puremagic.com/issues/show_bug.cgi?id=1861
Summary: .sort fails if opCmp takes ref param
Product: D
Version: 1.027
Platform: PC
OS/Version: Windows
Status: NEW
Severity: major
Priority: P2
Component: DMD
AssignedTo: bugzilla digitalmars.com
ReportedBy: wbaxter gmail.com
------
module opcmpref;
import std.stdio;
struct Pair
{
int a, b;
// Sort by b first then a
// Sorting fails if rhs is a 'ref' param. Ok if ref removed.
int opCmp(ref Pair rhs) {
if (b!=rhs.b) return b-rhs.b;
return a-rhs.a;
}
string toString()
{
return std.string.format("(%s,%s)",a,b);
}
}
void main()
{
// Single comparisons are all fine
assert( !(Pair(0,0)<Pair(0,0)) );
assert( !(Pair(1,0)<Pair(0,0)) );
assert( !(Pair(0,1)<Pair(0,0)) );
assert( !(Pair(1,1)<Pair(0,0)) );
assert( (Pair(0,0)<Pair(1,0)) );
assert( !(Pair(1,0)<Pair(1,0)) );
assert( !(Pair(0,1)<Pair(1,0)) );
assert( !(Pair(1,1)<Pair(1,0)) );
assert( (Pair(0,0)<Pair(0,1)) );
assert( (Pair(1,0)<Pair(0,1)) );
assert( !(Pair(0,1)<Pair(0,1)) );
assert( !(Pair(1,1)<Pair(0,1)) );
assert( (Pair(0,0)<Pair(1,1)) );
assert( (Pair(1,0)<Pair(1,1)) );
assert( (Pair(0,1)<Pair(1,1)) );
assert( !(Pair(1,1)<Pair(1,1)) );
// But sorting fails when opCmp takes 'ref' param
auto p = [Pair(0,0), Pair(3,0), Pair(2,1), Pair(1,4)];
p.sort;
writefln("p=",p);
assert(p[0] == Pair(0,0));
assert(p[1] == Pair(3,0));
assert(p[2] == Pair(2,1));
assert(p[3] == Pair(1,4));
}
------------
This may be something in the low-level lib rather than the compiler per-se.
I'm not sure about that. I have tested and found that the error happens with
both Phobos and Tango.
--
Feb 22 2008
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=1861
bugzilla digitalmars.com changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |INVALID
According to http://www.digitalmars.com/d/arrays.html, the parameter to a
struct's opCmp() must be S or S*, not ref S.
--
Feb 22 2008
http://d.puremagic.com/issues/show_bug.cgi?id=1861 Also, sort in std.algorithm should work with predicates that take references. --
Feb 22 2008
http://d.puremagic.com/issues/show_bug.cgi?id=1861
wbaxter gmail.com changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|major |enhancement
Status|RESOLVED |REOPENED
Resolution|INVALID |
Summary|.sort fails if opCmp takes |make .sort not fail if opCmp
|ref param |takes ref param
Ok, the documentation says either use Type or Type* for opCmp. The .sort
property does in fact work with either. The problem with just using Type* is
that it isn't called for regular struct comparisons like
Type a,b;
a<b
The problem with using just Type is that it makes sorting unnecessarily slow,
since value arguments will have to be copied for every call of the comparison
function.
It makes no sense not to allow ref. This is exactly the kind of thing ref was
meant for, where you want value semantics, but only want to pass a pointer
around.
Interestingly, if you provide BOTH a Type* and a ref Type version of opCmp,
then regular comparisons will use the ref version, and .sort will use the
pointer version.
But it would be nicer if ref just worked. I find it very surprising that it
doesn't, and until it does I would suggest that the documentation be changed to
say in very big bold letters that EVEN THOUGH REF MAY APPEAR TO WORK FOR SMALL
TEST CASES IT IS NOT SUPPORTED AND WILL FAIL IF YOU TRY TO .sort.
--
Feb 22 2008
http://d.puremagic.com/issues/show_bug.cgi?id=1861
Yao Gomez <yao.gomez gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |yao.gomez gmail.com
Version|1.027 |D1
Summary|.sort fails if opCmp takes |(D1 only) .sort fails if
|a ref param |opCmp takes a ref param
Marking this as D1 only, as the built-in, AA.sort method is going to be
deprecated.
With a slight modification, your test example passes and prints the correct
result with the std.algorithm.sort function (D2 only).
------
module opcmpref;
import std.stdio, std.algorithm;
struct Pair
{
int a, b;
// Sort by b first then a
// Sorting fails if rhs is a 'ref' param. Ok if ref removed.
int opCmp(ref Pair rhs) {
if (b!=rhs.b) return b-rhs.b;
return a-rhs.a;
}
property string toString()
{
return std.string.format("(%s,%s)",a,b);
}
}
void main()
{
// Single comparisons are all fine
assert( !(Pair(0,0)<Pair(0,0)) );
assert( !(Pair(1,0)<Pair(0,0)) );
assert( !(Pair(0,1)<Pair(0,0)) );
assert( !(Pair(1,1)<Pair(0,0)) );
assert( (Pair(0,0)<Pair(1,0)) );
assert( !(Pair(1,0)<Pair(1,0)) );
assert( !(Pair(0,1)<Pair(1,0)) );
assert( !(Pair(1,1)<Pair(1,0)) );
assert( (Pair(0,0)<Pair(0,1)) );
assert( (Pair(1,0)<Pair(0,1)) );
assert( !(Pair(0,1)<Pair(0,1)) );
assert( !(Pair(1,1)<Pair(0,1)) );
assert( (Pair(0,0)<Pair(1,1)) );
assert( (Pair(1,0)<Pair(1,1)) );
assert( (Pair(0,1)<Pair(1,1)) );
assert( !(Pair(1,1)<Pair(1,1)) );
auto p = [Pair(0,0), Pair(3,0), Pair(2,1), Pair(1,4)];
std.algorithm.sort(p);
// prints 'p=[(0,0), (3,0), (2,1), (1,4)]'
writefln("p=%s",p);
assert(p[0] == Pair(0,0));
assert(p[1] == Pair(3,0));
assert(p[2] == Pair(2,1));
assert(p[3] == Pair(1,4));
}
------
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