import std.string;
import std.array;
import std.algorithm;

void main()
{
	string[] sa = ["TOM","JOE","TOM4","TOM12","TOM6"];
	sort!(comp)(sa);
}
bool comp(string x, string y)
{
	string[] s = [x,y];
	return isSorted(s);
}

this code compiles find, but when run gives the following error:

core.exception.AssertError@./../../src/phobos/std/array.d(210): Attempting to fetch the front of an empty array

I'm using dmd2.030
same happens with dmd2.029

is that a bug?

A.M. wrote:
> import std.string;
> import std.array;
> import std.algorithm;
> 
> void main()
> {
> 	string[] sa = ["TOM","JOE","TOM4","TOM12","TOM6"];
> 	sort!(comp)(sa);
> }
> bool comp(string x, string y)
> {
> 	string[] s = [x,y];
> 	return isSorted(s);
> }
> 
> this code compiles find, but when run gives the following error:
> 
> core.exception.AssertError@./../../src/phobos/std/array.d(210): Attempting to fetch the front of an empty array
> 
> I'm using dmd2.030
> same happens with dmd2.029
> 
> is that a bug?

No. Because comp("foo", "foo") == true, but should return false when the two keys are equal.


BTW, the following code can reproduce your "bug":

import std.algorithm;
void main() {
   sort!("a <= b")( [2,1].dup );
}

KennyTM~ Wrote:

> No. Because comp("foo", "foo") == true, but should return false when the two keys are equal.
> 
> 
> BTW, the following code can reproduce your "bug":
> 
> import std.algorithm;
> void main() {
>     sort!("a <= b")( [2,1].dup );
> }

I guess that's why I should use   return x<y   and not   return x<=y   , btw I didn't know that "<" and the like work with strings.
I actually don't know why it swaps two elements which are equal. I guess it's something advanced.

Thanks for illustrating.

A.M. wrote:
> import std.string;
> import std.array;
> import std.algorithm;
> 
> void main()
> {
> 	string[] sa = ["TOM","JOE","TOM4","TOM12","TOM6"];
> 	sort!(comp)(sa);
> }
> bool comp(string x, string y)
> {
> 	string[] s = [x,y];
> 	return isSorted(s);
> }
> 
> this code compiles find, but when run gives the following error:
> 
> core.exception.AssertError@./../../src/phobos/std/array.d(210): Attempting to fetch the front of an empty array
> 
> I'm using dmd2.030
> same happens with dmd2.029
> 
> is that a bug?

The comp function must be an ordering function of the likes of "<", and yours is a very expensive way to compute x <= y. Sort does not work with "<=", only with "<".


Andrei

Andrei Alexandrescu Wrote:

> A.M. wrote:
> > import std.string;
> > import std.array;
> > import std.algorithm;
> > 
> > void main()
> > {
> > 	string[] sa = ["TOM","JOE","TOM4","TOM12","TOM6"];
> > 	sort!(comp)(sa);
> > }
> > bool comp(string x, string y)
> > {
> > 	string[] s = [x,y];
> > 	return isSorted(s);
> > }
> > 
> > this code compiles find, but when run gives the following error:
> > 
> > core.exception.AssertError@./../../src/phobos/std/array.d(210): Attempting to fetch the front of an empty array
> > 
> > I'm using dmd2.030
> > same happens with dmd2.029
> > 
> > is that a bug?
> 
> The comp function must be an ordering function of the likes of "<", and yours is a very expensive way to compute x <= y. Sort does not work with "<=", only with "<".
> 
> 
> Andrei

I actually changed it to:
return x<y

btw, this is not the actual code I'm writing, if it was I'd just use sort(sa) and not make my own comparing function.

A.M. wrote:
> Andrei Alexandrescu Wrote:
> 
>> A.M. wrote:
>>> import std.string;
>>> import std.array;
>>> import std.algorithm;
>>>
>>> void main()
>>> {
>>> 	string[] sa = ["TOM","JOE","TOM4","TOM12","TOM6"];
>>> 	sort!(comp)(sa);
>>> }
>>> bool comp(string x, string y)
>>> {
>>> 	string[] s = [x,y];
>>> 	return isSorted(s);
>>> }
>>>
>>> this code compiles find, but when run gives the following error:
>>>
>>> core.exception.AssertError@./../../src/phobos/std/array.d(210): Attempting to fetch the front of an empty array
>>>
>>> I'm using dmd2.030
>>> same happens with dmd2.029
>>>
>>> is that a bug?
>> The comp function must be an ordering function of the likes of "<", and yours is a very expensive way to compute x <= y. Sort does not work with "<=", only with "<".
>>
>>
>> Andrei
> 
> I actually changed it to:
> return x<y

Did things work after that replacement? (Thanks for the bug report too, regardless on whether it unveils an actual bug in std.algorithm.)

Andrei

Andrei Alexandrescu Wrote:

> A.M. wrote:
> > Andrei Alexandrescu Wrote:
> > 
> >> A.M. wrote:
> >>> import std.string;
> >>> import std.array;
> >>> import std.algorithm;
> >>>
> >>> void main()
> >>> {
> >>> 	string[] sa = ["TOM","JOE","TOM4","TOM12","TOM6"];
> >>> 	sort!(comp)(sa);
> >>> }
> >>> bool comp(string x, string y)
> >>> {
> >>> 	string[] s = [x,y];
> >>> 	return isSorted(s);
> >>> }
> >>>
> >>> this code compiles find, but when run gives the following error:
> >>>
> >>> core.exception.AssertError@./../../src/phobos/std/array.d(210): Attempting to fetch the front of an empty array
> >>>
> >>> I'm using dmd2.030
> >>> same happens with dmd2.029
> >>>
> >>> is that a bug?
> >> The comp function must be an ordering function of the likes of "<", and yours is a very expensive way to compute x <= y. Sort does not work with "<=", only with "<".
> >>
> >>
> >> Andrei
> > 
> > I actually changed it to:
> > return x<y
> 
> Did things work after that replacement? (Thanks for the bug report too, regardless on whether it unveils an actual bug in std.algorithm.)
> 
> Andrei

u mean, u don't know if it works or not?
well, I don't think I understand ur point, but anyway, of course it works.

btw, here is the complete code of my small application:

import std.stdio;
import std.string;
import std.array;
import std.conv;
import std.algorithm;
/*
   This program works as follows:
   there is a string[] of users with genders and their answers to a multichoice survey
   the program takes a user name as input, the user wants to find other users who answered at least a number (called similarity factor)
   of question as he/she did.
   the program then outputs a list of users who are ordered by how similar their answers to the user, if two users have the same
   similarity factor, they are then ordered by name.
*/
void main()
{
	string[] members=
	[
		"BETTY F M A A C C",
		"TOM3 M F A D C A",
		"TOM M F A D C A",
		"SUE F M D D D D",
		"ELLEN F M A A C A",
		"TOM6 M F A D C A",
		"JOE M F A A C A",
		"TOM12 M F A D C A",
		"ED M F A D D A",
		"SALLY F M C D A B",
		"MARGE F M A A C C",
		"TOM4 M F A D C A",
	];
//	the form is: "NAME G RG X X X .." where G is gender, RG is requested gender, X is the answer to a multichoice question.
	foreach (string s; bestmatch(members,"BETTY",2))
		writefln(s);
}
string[] bestmatch(string[] ms, string user, int sf)
{
	string[] u,tmp;
	foreach (string m; ms)
		if (((u=m.split())[0])==user) break;
	auto re = appender!(string[]);
	auto sa = appender!(int[]);
	int s;
	foreach (string m; ms)
	{
		s = 0;
		if ((tmp=m.split())[1]==u[2])
		{
			for (int i = 3; i<u.length; i++)
				if (tmp[i]==u[i]) s++;
		}
		if (s>=sf)
			re.put(join([to!(string)(s),tmp[0]]," "));
	}
	sort!(comp)(re.data);
	for (int i = 0; i<re.data.length; i++)
		re.data[i] = re.data[i].split()[1];
	return re.data;
}
bool comp(string x, string y)
{
	writefln("now: %s %s", x, y);
	string[] a = x.split(); string[] b = y.split();
	if (to!(int)(a[0])>to!(int)(b[0]))
		return 1;
	else if (a[1]<b[1])
		return 1;
	else
		return 0;
}
// END

Thanks Andrei for replying
Regards, A.M.

There was an error in my comp function in the code I have just posted, here is it after modification:

import std.stdio;
import std.string;
import std.array;
import std.conv;
import std.algorithm;
/*
   This program works as follows:
   there is a string[] of users with genders and their answers to a multichoice survey
   the program takes a user name as input, the user wants to find other users who answered at least a number (called similarity factor)
   of question as he/she did.
   the program then outputs a list of users who are ordered by how similar their answers to the user, if two users have the same
   similarity factor, they are then ordered by name.
*/
void main()
{
	string[] members=
	[
		"BETTY F M A A C C",
		"TOM3 M F A D C A",
		"TOM M F A D C A",
		"SUE F M D D D D",
		"ELLEN F M A A C A",
		"TOM6 M F A D C A",
		"JOE M F A A C A",
		"TOM12 M F A D C A",
		"ED M F A D D A",
		"SALLY F M C D A B",
		"MARGE F M A A C C",
		"TOM4 M F A D C A",
	];
//	the form is: "NAME G RG X X X .." where G is gender, RG is requested gender, X is the answer to a multichoice question
	foreach (string s; bestmatch(members,"BETTY",2))
		writefln(s);
}
string[] bestmatch(string[] ms, string user, int sf)
{
	string[] u,tmp;
	foreach (string m; ms)
		if (((u=m.split())[0])==user) break;
	auto re = appender!(string[]);
	auto sa = appender!(int[]);
	int s;
	foreach (string m; ms)
	{
		s = 0;
		if ((tmp=m.split())[1]==u[2])
		{
			for (int i = 3; i<u.length; i++)
				if (tmp[i]==u[i]) s++;
		}
		if (s>=sf)
			re.put(join([to!(string)(s),tmp[0]]," "));
	}
	sort!(comp)(re.data);
	for (int i = 0; i<re.data.length; i++)
		re.data[i] = re.data[i].split()[1];
	return re.data;
}
bool comp(string x, string y)
{
	writefln("now: %s %s", x, y);
	string[] a = x.split(); string[] b = y.split();
	int cmp = (to!(int)(a[0])>to!(int)(b[0]));
	if (cmp>0)
		return 1;
	else if (cmp==0 && a[1]<b[1])
		return 1;
	return 0;
}