pure-lang-users

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Jeremy Voorhis wrote:
> OMG $$++

That gives me a syntax error. ;-) But look at this marvel!

   > OMG = id;
   > OMG $ (Im,feeling,silly)!2 $ OMG ponies;
   silly ponies

Ok, I take it that $$ is the consensus.

> Regarding tuples, I've always thought of tuples as representing
> structures with a fixed number of slots, and that this was a perfectly
> valid thing to do.

That's what they are, but Pure also allows you to piece them together 
and manipulate them in any way you see fit. Also, in Haskell et al 
tuples are a builtin data structure, whereas in Pure they are just an 
algebraic type like any other (and are in fact completely defined in the 
prelude).

> My Pure abilities are still weak, so somebody help
> me out – I assumed tagged tuples would be useful for representing
> algebraic types in a dynamic language like Pure, since they are good
> for matching on.

That's what poor Erlang programmers have to do. In Pure all your data is 
in fact a term algebra, so any function symbol can act as a constructor 
and you don't need this kludge. E.g., nil and bin act as constructors in 
the following example:

nullary nil;

insert nil y		= bin y nil nil;
insert (bin x L R) y	= bin x (insert L y) R if y<x;
			= bin x L (insert R y) otherwise;

(That works without having to declare anything, except a nullary symbol 
like nil so that the compiler can distinguish it from a variable when it 
occurs on the lhs of an eqn.)

Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Libor S. <li...@gm...>]

On Fri, 15 Aug 2008 02:16:40 +0100, Albert Graef <Dr....@t-...> wrote:

> Libor Spacek wrote:
>> I am not entirely convinced that the tuples are even worth having at all.
>> For the minimal (flatness) distinction, they ship in a lot of confusion.
>
> Can you elaborate on that? The only complication I see is the borked
> list-of-tuples syntax, and I'm about to fix that (hopefully!).
>

Both lists and tuples are devices for ordering and grouping some items.

I do not see the problem with using a pair of brackets to make the grouping explicit, as in the list [1,2,3] instead of relying on the precendence of the associativity and using a tuple 1,2,3. I have learnt through painful experience not to rely on remembering the exact precedence
of numerous associative operators, especially when I can add my own.

Maybe it is just me but when using Pure, I am always worrying: 'is this a tuple or is it a list?' I need to worry about it because selectors and functions will typically work only on one but not on the other. To give a trivial example:

head (1..3); // is OK
head (1,2,3); // is not OK

So, if I return 1,2,3 instead of [1,2,3], everything falls down round my ears.
I guess you will say that I ought to know better and you will be right.

To complicate things further, I can also in many situations use simply 1 2 3, e.g.
>let a = 1 2 3;
>a;
1 2 3

So there are three ways of ordering and grouping items which are nearly the same but not quite,
which I, at least, find  a little bewildering.

L.

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Libor Spacek wrote:
> Maybe it is just me but when using Pure, I am always worrying: 'is this a tuple or is it a list?'

Ok, I see. But I think that like so many things it's just a matter of 
practice, getting to know the language. I agree that having an extra 
tuple type makes things more complex, but, as I tried to point out in a 
previous post, it also makes some stuff more readable or familiar.

If you come from a language like Haskell or Erlang where you're working 
with tuples all them time, then you'd surely miss them if they weren't 
provided. Real Lisp men of course don't need all that sugar. ;-) But 
language design is always a compromise, and every PL is a new exercise 
to find a certain sweet spot between simplicity, power and convenience. 
If you leave away everything that's not strictly needed, then you'll end 
up with combinatorial calculus without any builtins, but who would want 
to program in such a language?

Of course, Pure's tuples being flat is a ... hmm ... speciality that 
takes some time getting used to. But I wanted to have tuples in Pure for 
notational convenience, and this was a really cheap way to get them at 
the cost of just a single infix operator, requiring no builtins at all. 
So yes, they're an ideosyncrasy, but I dare say that they're also 
elegant in a way, IMNSHO.

> To complicate things further, I can also in many situations use simply 1 2 3, e.g.
>> let a = 1 2 3;

You don't want to do that. If your first element happens to be a hungry 
closure then you're busted. :)

Cheers,
Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Eddie R. <er...@bm...>]

On Fri, 2008-08-15 at 12:48 +0100, Libor Spacek wrote:

> To complicate things further, I can also in many situations use simply 1 2 3, e.g.
> >let a = 1 2 3;
> >a;
> 1 2 3

Hey Libor, that's cute! Tain't thought of that one. But, ... How do you
get at the elements? Would be nice if we could have something like 
 [1 2 3 4] (where the spaces are any white space) without the commas so
I could copy and paste from the clipboard straight into the interpreter.
That is one great thing about DrScheme:
Start with at the prompt

 > (histogram '())

or whatever function you need. Highlight the data from a Word (Soffice)
or Spreadsheet, or Web table, middle button click the stuff between the
'() in DrScheme and 

(histogram '(10 32 34 56 ...))

Except they are 'tabs' or 'end of lines' instead of spaces hit the 'end'
key and press 'enter' and watch the magic happen. It's an X thing.
Cannot do that with Windoze.

e.r.

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

> - First and foremost, I want to see whether I can massage the grammar so 
> that it becomes possible to write lists of tuples using the special case 
> syntax [(1,2),(3,4),...].

This is now implemented (r521). Probably the most important single 
cosmetic change in this release. :)

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Albert Graef wrote:
> - The discussion I had with Libor about how to implement a sequencing 
> operator ("first x, then y") also kept me thinking, because the solution 
> I proposed there is not tail-recursive. To do this in a proper way, we'd 
> need a built-in sequencing operator (special form). While it's not 
> strictly needed, it's much more convenient than having to write 'y when 
> _ = x end' all the time.

This is now implemented as well. ($$ operator)

I'm basically through with my 0.5 TODO list now (Windows port 
notwithstanding; I can hopefully take a look at that later today). So if 
anyone is still listening, it would be nice if you could take the latest 
svn for a test drive. ;-)

I also vaguely recall that someone volunteered to write a little test 
module for math.pure, or did I just dream that up? :)

Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Eddie R. <er...@bm...>]

On Mon, 2008-08-18 at 14:08 +0200, Albert Graef wrote:
> Albert Graef wrote:
> > - The discussion I had with Libor about how to implement a sequencing 
> > operator ("first x, then y") also kept me thinking, because the solution 
> > I proposed there is not tail-recursive. To do this in a proper way, we'd 
> > need a built-in sequencing operator (special form). While it's not 
> > strictly needed, it's much more convenient than having to write 'y when 
> > _ = x end' all the time.
> 
> This is now implemented as well. ($$ operator)
> 
> I'm basically through with my 0.5 TODO list now (Windows port 
> notwithstanding; I can hopefully take a look at that later today). So if 
> anyone is still listening, it would be nice if you could take the latest 
> svn for a test drive. ;-)
> 
> I also vaguely recall that someone volunteered to write a little test 
> module for math.pure, or did I just dream that up? :)

Was that me? I'll see what I can do ASAP.

e.r.

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Eddie Rucker wrote:
>> I also vaguely recall that someone volunteered to write a little test 
>> module for math.pure, or did I just dream that up? :)
> 
> Was that me? I'll see what I can do ASAP.

Not sure, but it would be much appreciated anyway. :)

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Eddie R. <er...@bm...>]

Something bad is happening here for the complex numbers:

 > sqrt (1+:2);
 2.23606797749979*cos (t/2)+:2.23606797749979*sin (t/2)

the angle t is missing.

Another nice way of doing this is:

sqrt (x+:y) = sqrt (0.5*(r+a)) +: sqrt (0.5*(r-a))
              when
                r = sqrt x*x+y*y;
              end; 

e.r.

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Eddie Rucker wrote:
>>  > sqrt (1+:2);
>>  2.23606797749979*cos (t/2)+:2.23606797749979*sin (t/2)

Oops. Fixed.

>> Another nice way of doing this is:
>>
>> sqrt (x+:y) = sqrt (0.5*(r+a)) +: sqrt (0.5*(r-a))
>>               when
>>                 r = sqrt x*x+y*y;
>>               end; 

a = ?

> Oops. That r should be r = sqrt (x*x+y*y).

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Eddie Rucker wrote:
> IMHO, the following rules should be added for pow:
> 
> pow n::int (x%y)        |
> pow n::bigint (x%y)     |
> pow n::double (x%y)     = pow n (x/y);

Yes, you're right, I've added these now.

Thanks,
Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Eddie R. <er...@bm...>]

On Mon, 2008-08-18 at 19:49 +0200, Albert Graef wrote:
> Eddie Rucker wrote:
> > IMHO, the following rules should be added for pow:
> > 
> > pow n::int (x%y)        |
> > pow n::bigint (x%y)     |
> > pow n::double (x%y)     = pow n (x/y);
> 
> Yes, you're right, I've added these now.

After the last svn update I'm getting:
 > using math;
 > pow 3 (4%3);
 warning: rule never reduced: pow n::int (x%y) = pow n (x/y);
 warning: rule never reduced: pow n::bigint (x%y) = pow n (x/y);
 warning: rule never reduced: pow n::double (x%y) = pow n (x/y);
 4.32674871092222
 > 

When I looked in math.pure you have the following rules:

pow (x%y) n::int	|
pow (x%y) n::bigint	= pow x n % pow y n if n>0;
			= pow y (-n) % pow x (-n) if n<0;
			= 1L%1L otherwise;
pow (x%y) n::double	= pow (x/y) n;
pow (x%y) (n%m)		= pow (x/y) (n/m);
pow x::int (n%m)        |
pow x::bigint (n%m)     |
pow x::double (n%m)     = pow x (n/m);

pow n::int (x%y)        |
pow n::bigint (x%y)     |
pow n::double (x%y)     = pow n (x/y);

You might want to cut the last three out?

e.r.

Re: [pure-lang-users] Proposed syntax changes

[Eddie R. <er...@bm...>]

Sorry.

 sqrt (x+:y) = sqrt (0.5*(r+x)) +: sqrt (0.5*(r-x))
               when
                 r = sqrt x*x+y*y;
               end; 

Re: [pure-lang-users] Proposed syntax changes

[Eddie R. <er...@bm...>]

Use to be, 0.5*x produced faster code than x/2.0. Well, I was pleasantly
surprised with the assembly output of "gcc -S -O2 test.c" produced
exactly the same output.

test.c:
------------------------------
#include <stdio.h>

int main(void) {
  double a, b, c;

  printf("Enter first num:");
  scanf("%g", &a);
  printf("Enter second num:");
  scanf("%g", &b);
  c = a/2.0;
  printf("%g\n", c);
  c = 0.5*b;
  printf("%g\n", c);
  return 0;
}
-----------------------------
Portion of the assembly:
-----------------------------
call	scanf
	movsd	.LC3(%rip), %xmm0
	movl	$.LC4, %edi
	movl	$1, %eax
	mulsd	16(%rsp), %xmm0
	call	printf
	movsd	.LC3(%rip), %xmm0
	movl	$.LC4, %edi
	movl	$1, %eax
	mulsd	8(%rsp), %xmm0
	call	printf

e.r.

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Eddie Rucker wrote:
> Use to be, 0.5*x produced faster code than x/2.0. Well, I was pleasantly
> surprised with the assembly output of "gcc -S -O2 test.c" produced
> exactly the same output.

Doesn't make a difference with Pure either, in fact even x/2 runs every 
bit as fast, and looks nicer.

I've committed that version now.

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Eddie Rucker wrote:
> Sorry.
> 
>  sqrt (x+:y) = sqrt (0.5*(r+x)) +: sqrt (0.5*(r-x))
>                when
>                  r = sqrt x*x+y*y;
>                end; 

That looks neat, I think I'm going to use that. :)

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Eddie R. <er...@bm...>]

sqrt is usually faster than sin and cos both in floating point hardware
and software.

e.r.

On Tue, 2008-08-19 at 01:16 +0200, Albert Graef wrote:
> Eddie Rucker wrote:
> > Sorry.
> > 
> >  sqrt (x+:y) = sqrt (0.5*(r+x)) +: sqrt (0.5*(r-x))
> >                when
> >                  r = sqrt x*x+y*y;
> >                end; 
> 
> That looks neat, I think I'm going to use that. :)
> 

Re: [pure-lang-users] Proposed syntax changes

[Eddie R. <er...@bm...>]

On Mon, 2008-08-18 at 18:25 -0500, Eddie Rucker wrote:

Dang!
I keep forgetting to put parenthesis around the r = sqrt (x*x+y*y)

e.r.

> sqrt is usually faster than sin and cos both in floating point hardware
> and software.
> 
> e.r.
> 
> On Tue, 2008-08-19 at 01:16 +0200, Albert Graef wrote:
> > Eddie Rucker wrote:
> > > Sorry.
> > > 
> > >  sqrt (x+:y) = sqrt (0.5*(r+x)) +: sqrt (0.5*(r-x))
> > >                when
> > >                  r = sqrt x*x+y*y;
> > >                end; 
> > 
> > That looks neat, I think I'm going to use that. :)
> > 
> 
> 
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Re: [pure-lang-users] Proposed syntax changes

[Ryan S. <rya...@us...>]

On Aug 18, 2008, at 07:08, Albert Graef wrote:

> I'm basically through with my 0.5 TODO list now (Windows port
> notwithstanding; I can hopefully take a look at that later today).  
> So if
> anyone is still listening, it would be nice if you could take the  
> latest
> svn for a test drive. ;-)


Ok, I tested r534 on Mac OS X 10.5 Leopard.
The install_name stuff is working, so I could remove my patch, thanks.
The prelude test failed; the log is attached.
The issue with the pass or fail being printed on the next line on  
Leopard hasn't been resolved yet.

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Ryan Schmidt wrote:
> The prelude test failed; the log is attached.

Probably not a big issue, given that all other tests pass.

Could you please run the following:

rm test/prelude.log && make logs

Then please send me the newly created test/prelude.log so that I can 
figure out where it differs on your system.

Thanks,
Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Ryan S. <rya...@us...>]

On Aug 18, 2008, at 18:51, Albert Graef wrote:

> Ryan Schmidt wrote:
>> The prelude test failed; the log is attached.
>
> Probably not a big issue, given that all other tests pass.
>
> Could you please run the following:
>
> rm test/prelude.log && make logs
>
> Then please send me the newly created test/prelude.log so that I can
> figure out where it differs on your system.

After running "rm test/prelude.log && make logs", "svn diff test"  
shows no differences.

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Ryan Schmidt wrote:
> After running "rm test/prelude.log && make logs", "svn diff test"  
> shows no differences.

Surely not, but I need your version of the file now to compare against 
my "golden" log. :)

Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Ryan S. <rya...@us...>]

On Aug 18, 2008, at 19:05, Albert Graef wrote:

> Ryan Schmidt wrote:
>> After running "rm test/prelude.log && make logs", "svn diff test"
>> shows no differences.
>
> Surely not, but I need your version of the file now to compare against
> my "golden" log. :)

Here it is, but it is the same prelude.log that is in your repository  
(hence no differences shown by "svn diff")

Re: [pure-lang-users] Proposed syntax changes

[Albert G. <Dr....@t-...>]

Ryan Schmidt wrote:
> Here it is, but it is the same prelude.log that is in your repository 
> (hence no differences shown by "svn diff")

Sorry, it was late. ;-)

But if regenerating the log doesn't show any differences, then it 
shouldn't fail on 'make check' either. Does it still fail there?

Can you please send me the output of this command:
DYLD_LIBRARY_PATH=. PURELIB=lib ./pure -n -v7 lib/prelude.pure | diff 
test/prelude.log -

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag

Re: [pure-lang-users] Proposed syntax changes

[Ryan S. <rya...@us...>]

On Aug 19, 2008, at 00:59, Albert Graef wrote:

> Ryan Schmidt wrote:
>
>> Here it is, but it is the same prelude.log that is in your repository
>> (hence no differences shown by "svn diff")
>
> Sorry, it was late. ;-)
>
> But if regenerating the log doesn't show any differences, then it
> shouldn't fail on 'make check' either. Does it still fail there?
>
> Can you please send me the output of this command:
> DYLD_LIBRARY_PATH=. PURELIB=lib ./pure -n -v7 lib/prelude.pure | diff
> test/prelude.log -

No output!


Separately: I tested on Tiger. There, prelude.pure and all other  
tests pass, except test017.pure which fails. I deleted test017.log  
and ran "make logs", and test017.log is different; attached.