pure-lang-users Mailing List for Pure (Page 17)

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Sorry for sending this twice. I thought it failed to send the first
time.

e.r.

Hi guys!

In Q we could write:

(X+A)*(X+B) = X^2+(A+B)*X+(A*B);

as an equation and Q would happily reduce 

(X+2)*(X+4);

to

X^2+6*X+8

which was nice. But in Pure, since we cannot repeat a variable on the
left hand side, we cannot do any of these nice equations:

X*Y+X*Z = X*(Y+Z);
X/X = 1 if X != 0;
X+N*X = (N+1)*X;

etc...

Albert, I know you made an === operator but how are we suppose to use it
to handle this sort of stuff?

Ok. I've figured I need to do stuff like 

(a*b)+(c*d) = (a+c)*b if b === d;
a*b=a^2 if a===b;
(a+b)*(c+d) = a*c+a*d+b*c+b*d;
a*b = b*a if numberp b;

Then
  > (x+4)*(x+3)
  x^2+3*x+4*x+12

Why doesn't the rule '(a*b)+(c*d) = (a+c)*b if b === d;' reduce it
further to 

x^2+7x+12

since 
  > 3*x+4*x

reduces to
  7*x

e.r.

Hi guys!

In Q we could write:

(X+A)*(X+B) = X^2+(A+B)*X+(A*B);

as an equation and Q would happily reduce 

(X+2)*(X+4);

to

X^2+6*X+8

which was nice. But in Pure, since we cannot repeat a variable on the
left hand side, we cannot do any of these nice equations:

X*Y+X*Z = X*(Y+Z);
X/X = 1 if X != 0;
X+N*X = (N+1)*X;

etc...

Albert, I know you made an === operator but how are we suppose to use it
to handle this sort of stuff?

Ok. I've figured I need to do stuff like 

(a*b)+(c*d) = (a+c)*b if b === d;
a*b=a^2 if a===b;
(a+b)*(c+d) = a*c+a*d+b*c+b*d;
a*b = b*a if numberp b;

Then
  > (x+4)*(x+3)
  x^2+3*x+4*x+12

Why doesn't the rule '(a*b)+(c*d) = (a+c)*b if b === d;' reduce it
further to 

x^2+7x+12

since 
  > 3*x+4*x

reduces to
  7*x

e.r.

I am on a short holiday, will be back on Sunday, looking forward to getting
back to Pure then.
Libor

On Tue 22/07/08  5:45 PM , Albert Graef Dr....@t-... sent:
> Eddie Rucker wrote:
> > What's up with svn? Usually, I can go there using
> firefox and pull up> libraries, runtime.hh, etc. for documentation purposes.
> For the last> week (except a few short period times) I haven't been
> able to browse> svn.
> 
> Yes, ViewVC seems to be disabled for now, apparently some overhaul of 
> the SVN infrastructure is in progress. More info on the (new) site 
> status page at http://sourceforge.net/sitestatus. We can also
> joyfully look forward to a pending migration and major update of the shell/web 
> services which probably means that this will soon be broken, too. :(
> 
> Albert
> 

Major bummer :-(

Eddie Rucker wrote:
> What's up with svn? Usually, I can go there using firefox and pull up
> libraries, runtime.hh, etc. for documentation purposes. For the last
> week (except a few short period times) I haven't been able to browse
> svn.

Yes, ViewVC seems to be disabled for now, apparently some overhaul of 
the SVN infrastructure is in progress. More info on the (new) site 
status page at http://sourceforge.net/sitestatus. We can also joyfully 
look forward to a pending migration and major update of the shell/web 
services which probably means that this will soon be broken, too. :(

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

Hi all!

What's up with svn? Usually, I can go there using firefox and pull up
libraries, runtime.hh, etc. for documentation purposes. For the last
week (except a few short period times) I haven't been able to browse
svn.

e.r.

On Mon, 2008-07-21 at 23:20 +0200, Jiri Spitz wrote:
> Eddie Rucker wrote:
> > Shouldn't
> >  > list (1,2,3);
> >  >
> > 
> > return [1,2,3]?
> > 
> > On my machine it doesn't return anything.
> > 
> List is an interpreter command. You have to prefix the the line with a 
> space to distinguish the function list from the command list " list 
> (1,2,3);".
> 
> Jiri

Yep, that did the trick. Thanks!

e.r.

Eddie Rucker wrote:
> Shouldn't
>  > list (1,2,3);
>  >
> 
> return [1,2,3]?
> 
> On my machine it doesn't return anything.
> 
List is an interpreter command. You have to prefix the the line with a 
space to distinguish the function list from the command list " list 
(1,2,3);".

Jiri

Hi Albert,

Shouldn't
 > list (1,2,3);
 >

return [1,2,3]?

On my machine it doesn't return anything.

e.r.

The W3C has issued a new draft of the unified entity definitions,
updating the names phi, lang, rang, OverParenthesis, UnderParenthesis,
OverBrace, UnderBrace, lbbrk, and rbbrk.

The new entity definition file is at
http://www.w3.org/2003/entities/2007/w3centities-f.ent .

Q and Pure should be updated accordingly; TagSoup will be.

-- 
John Cowan  <co...@cc...>  http://ccil.org/~cowan
Micropayment advocates mistakenly believe that efficient allocation of
resources is the purpose of markets.  Efficiency is a byproduct of market
systems, not their goal.  The reasons markets work are not because users
have embraced efficiency but because markets are the best place to allow
users to maximize their preferences, and very often their preferences are
not for conservation of cheap resources.  --Clay Shirkey

On Mon, 2008-07-21 at 16:36 +0200, Jiří Spitz wrote:
> Eddie Rucker wrote:
> > When I tried to test a script I had written using notepad on my Linux
> > box I got the following errors.
> > 
> > erucker@erucker:~/Desktop$ pure -i test.pure
> > 'est.pure:4.8: invalid character '
> > test.pure:4.8: syntax error, unexpected invalid character
> > 'est.pure:5.14: invalid character '
> > test.pure:6.28: syntax error, unexpected ']', expecting '=' or '|'
> > test.pure:6.62-64: syntax error, unexpected ']', expecting '=' or '|'
> > 'est.pure:6.66: invalid character '
> > ...
> > 
> This is problem of different file formats on Linux and Windows. Windows' 
> text files have lines delimited by CR+LF characters wheras Linux' ones 
> only by LF. Files created under Windows exhibit the described behaviour 
> under Linux. Most programers' text editors (not Notepad) allow change 
> the file format.

I'm not too familiar with Windoze but I knew about the \r\n sequences. I
had to write the script on someone else's machine (who doesn't want
another text editor) and I had to test it on my Linux box. It just seems
strange that 

e.r.

Eddie Rucker wrote:
> When I tried to test a script I had written using notepad on my Linux
> box I got the following errors.
> 
> erucker@erucker:~/Desktop$ pure -i test.pure
> 'est.pure:4.8: invalid character '
> test.pure:4.8: syntax error, unexpected invalid character
> 'est.pure:5.14: invalid character '
> test.pure:6.28: syntax error, unexpected ']', expecting '=' or '|'
> test.pure:6.62-64: syntax error, unexpected ']', expecting '=' or '|'
> 'est.pure:6.66: invalid character '
> ...
> 
This is problem of different file formats on Linux and Windows. Windows' 
text files have lines delimited by CR+LF characters wheras Linux' ones 
only by LF. Files created under Windows exhibit the described behaviour 
under Linux. Most programers' text editors (not Notepad) allow change 
the file format.

Jiri

On Mon, 2008-07-21 at 09:20 -0500, Eddie Rucker wrote:
> Hi Albert,

> qsort p [] = [];
> qsort p (x:xs)
>   = sort p [l; l = xs; l < x] + (x : sort p [r; r = xs; r >= x])
>     with
>       x < y = p x y;
>       x >= y = not p x y;
>     end;
BTW, I hope you don't mind that I ripped off your qsort ;-)

e.r.

Hi Albert,

When I tried to test a script I had written using notepad on my Linux
box I got the following errors.

erucker@erucker:~/Desktop$ pure -i test.pure
'est.pure:4.8: invalid character '
test.pure:4.8: syntax error, unexpected invalid character
'est.pure:5.14: invalid character '
test.pure:6.28: syntax error, unexpected ']', expecting '=' or '|'
test.pure:6.62-64: syntax error, unexpected ']', expecting '=' or '|'
'est.pure:6.66: invalid character '
...

Notice that it says 'est.pure...' instead of 'Test.pure...' Anyway, the
first few lines of the source were:

qsort p [] = [];
qsort p (x:xs)
  = sort p [l; l = xs; l < x] + (x : sort p [r; r = xs; r >= x])
    with
      x < y = p x y;
      x >= y = not p x y;
    end;

When, I opened the file from emacs, I noticed all of the ^M ('\r's) at
the end of each line. After removing them, the script runs fine. To say
the least, it was a hard bug to find because the script looked just fine
from Kate.

e.r.

Eddie Rucker wrote:
> Personally, I prefer 'when end' to 'when begin end.'

Me too, obviously. :) Pascal's begin ... end goes back to Algol, but 
Wirth himself later realized that properly bracketed statements are 
better and more economic, so that's what Modula and Oberon have.

> However, 'when {}' isn't bad but I figure you'll use '{}' for streams.

Either that, or structs, or generalized list comprehensions. In any case 
it seems like a good idea to keep {} unused for now.

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

On Mon, 2008-07-21 at 05:33 +0200, Albert Graef wrote:
> Eddie Rucker wrote:
> > What do you think about the following addition to syntax? If there is exactly one statement
> > inside of a 'with' or when 'block,' we could leave off the 'end.'
> 
> Yeah, that would be convenient, but unfortunately it's not possible, 
> since the grammar would become ambiguous (or non-LALR at least).
> 
> Albert
> 
Ok, I forgot Pascal used 'begin end' pairs to define a block.
Personally, I prefer 'when end' to 'when begin end.' However, 'when {}'
isn't bad but I figure you'll use '{}' for streams.

e.r.

On Mon, 2008-07-21 at 05:23 +0200, Albert Graef wrote:
> Eddie Rucker wrote:
> >> [v; v = map (\rw -> rw!2 + rw!4) ranked; v > 0];
> > 
> > Thanks Jiri, that works, but it is still not in the list comprehension spirit (without filter, map, fold, and zip)
> > I was looking for.
> 
> How about:
> 
> [v; v = [rw!2 + rw!4; rw = ranked]; v > 0];
> 
> (Haven't checked this, though.)
> 
That's the ticket! Jiri's map as a list comprehension and I should have
seen that. Not making any excuses, but this sinus headache for the last
few days has got me all messed up.

e.r.

Eddie Rucker wrote:
> What do you think about the following addition to syntax? If there is exactly one statement
> inside of a 'with' or when 'block,' we could leave off the 'end.'

Yeah, that would be convenient, but unfortunately it's not possible, 
since the grammar would become ambiguous (or non-LALR at least).

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

Ryan Schmidt wrote:
> Ok, pure r438 works with llvm-devel at 53722 so that's fine. The pure- 
> devel port is updated!

Thanks. So it seems that there are still some OSX bugs in LLVM 2.3 which 
are fixed in the latest LLVM from svn? I should probably mention that in 
the INSTALL file somewhere.

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

Eddie Rucker wrote:
>> [v; v = map (\rw -> rw!2 + rw!4) ranked; v > 0];
> 
> Thanks Jiri, that works, but it is still not in the list comprehension spirit (without filter, map, fold, and zip)
> I was looking for.

How about:

[v; v = [rw!2 + rw!4; rw = ranked]; v > 0];

(Haven't checked this, though.)

-- 
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

On Sun 20/07/08  3:40 PM , Jiri Spitz jir...@bl... sent:
> Eddie Rucker wrote:
> > Is there a way to create a new value from separate
> values inside a list comprehension?> 
> > ranked is a list of lists. I want to addelement 2 and 4
> and record the result if > it is positive. Yes, it is trival to do without a list
> comprehension but I want> to do it with one.
> > 
> > [v; v > 0; v = rw!2 + rw!4; rw = ranked];
> > 
> > I know this doesn't work;
> > 
> > [v; rw = ranked; v > 0] when v = rw!2 + rw!4
> end;> 
> E. g. this way:
> 
> [v; v = map (\rw -> rw!2 + rw!4) ranked; v > 0];

Thanks Jiri, that works, but it is still not in the list comprehension spirit (without filter, map, fold, and zip)
I was looking for.

If not using list comprehensions, I think a filter_map and filter_fold like the filter-map that srfi 1 offers 
would be efficient for things like this. I'll add filter_map and filter_fold to my TODO list utility library.

e.r.

Eddie Rucker wrote:
> Is there a way to create a new value from separate values inside a list comprehension?
> 
> ranked is a list of lists. I want to addelement 2 and 4 and record the result if 
> it is positive. Yes, it is trival to do without a list comprehension but I want
> to do it with one.
> 
> [v; v > 0; v = rw!2 + rw!4; rw = ranked];
> 
> I know this doesn't work;
> 
> [v; rw = ranked; v > 0] when v = rw!2 + rw!4 end;
> 
E. g. this way:

[v; v = map (\rw -> rw!2 + rw!4) ranked; v > 0];

Jiri

Hi Albert,

What do you think about the following addition to syntax? If there is exactly one statement
inside of a 'with' or when 'block,' we could leave off the 'end.'

Instead of 

with
  rule1
end;

we could have

with rule1;

e.r.

Is there a way to create a new value from separate values inside a list comprehension?

ranked is a list of lists. I want to addelement 2 and 4 and record the result if 
it is positive. Yes, it is trival to do without a list comprehension but I want
to do it with one.

[v; v > 0; v = rw!2 + rw!4; rw = ranked];

I know this doesn't work;

[v; rw = ranked; v > 0] when v = rw!2 + rw!4 end;

e.r.

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