D - String Comparison and Dynamic Arrays?

Gary (19/19) Mar 26 2002 Walter,

Pavel Minayev (7/17) Mar 26 2002 Currently, you cannot use == and friends to compare strings, and

Gary (5/23) Mar 26 2002 Walter... Any comments?

Walter (10/16) Mar 26 2002 I disabled setting array.length for operators other than assignment beca...

Gary (5/22) Mar 26 2002 lvalue)

Walter (18/23) Mar 26 2002 need,

Gary (6/29) Mar 26 2002 input

Walter (4/6) Mar 26 2002 was

Russ Lewis (27/30) Mar 27 2002 How about some sort of array index syntax that automatically doubles the...

Russ Lewis (7/9) Mar 27 2002 Oops, meant to type

OddesE (10/19) Mar 27 2002 tripling

Gary (5/22) Mar 26 2002 Also... when do you expect string comparison to be incorporated?
Pavel Minayev (10/14) Mar 26 2002 because

Walter (4/18) Mar 26 2002 Because then I'd be spending my life explaining why ++ is not implemente...

Pavel Minayev (5/7) Mar 27 2002 Then, implement ++ as if a new element with default value of desired typ...

Walter (6/13) Mar 29 2002 implemented

Pavel Minayev (6/12) Mar 29 2002 type

Walter (4/11) Mar 29 2002 Yes, but ~= is useful for concatenating strings with more than one entry...

Pavel Minayev (13/15) Mar 29 2002 ++

Walter (4/14) Apr 07 2002 That turned out to have problems implementing it. The trouble was if som...

Pavel Minayev (4/19) Apr 07 2002 someone

Walter (7/26) Apr 07 2002 char[] a = new char[10];

Pavel Minayev (3/8) Apr 08 2002 Hm... I thought that, when length increases, the memory is reallocated!

Walter (3/11) Apr 12 2002 Yes, and it must be because of that scenario above.

Sean L. Palmer (11/28) Mar 27 2002 Why not just double the darray's allocated space when array.length++ exc...

OddesE (13/20) Mar 27 2002 exceeds

OddesE (5/6) Mar 27 2002 Delphi typo... :)

"Gary" <gedumer bcpl.net> writes:

Walter,

I can successfully use the switch/case construct to compare equality of a
string, but the same can't be said for using the "if" statement. For
example:
  if (a == "Hello") ...
doesn't succeed.
whereas:
  switch (a)
  {
    case "Hello": ...
  }
does work.

I'm also getting an error during compile ('array.length' is not an lvalue)
with the following:
  int[] array;

  array[array.length++] = 0;
  array[array.length++] = 1;
  array[array.length] = 2;

Gary.

Mar 26 2002

"Pavel Minayev" <evilone omen.ru> writes:

"Gary" <gedumer bcpl.net> wrote in message
news:a7qll4$1870$1 digitaldaemon.com...

 I can successfully use the switch/case construct to compare equality of a
 string, but the same can't be said for using the "if" statement. For
 example:
   if (a == "Hello") ...
 doesn't succeed.

Currently, you cannot use == and friends to compare strings, and
arrays in general. You have to use cmp():

    if (!cmp(a, "Hello")) ...

Hopefully some operator to compare arrays will be added.


 I'm also getting an error during compile ('array.length' is not an lvalue)
 with the following:
   int[] array;

   array[array.length++] = 0;
   array[array.length++] = 1;

This one (and array.length--) I was asking once, but no luck =)

Mar 26 2002

"Gary" <gedumer bcpl.net> writes:

Walter... Any comments?

Pavel Minayev <evilone omen.ru> wrote in message
news:a7qnim$19c9$1 digitaldaemon.com...
 "Gary" <gedumer bcpl.net> wrote in message
 news:a7qll4$1870$1 digitaldaemon.com...

 I can successfully use the switch/case construct to compare equality of


a
 string, but the same can't be said for using the "if" statement. For
 example:
   if (a == "Hello") ...
 doesn't succeed.

 Currently, you cannot use == and friends to compare strings, and
 arrays in general. You have to use cmp():

     if (!cmp(a, "Hello")) ...

 Hopefully some operator to compare arrays will be added.


 I'm also getting an error during compile ('array.length' is not an


lvalue)
 with the following:
   int[] array;

   array[array.length++] = 0;
   array[array.length++] = 1;

 This one (and array.length--) I was asking once, but no luck =)

Mar 26 2002

"Walter" <walter digitalmars.com> writes:

"Gary" <gedumer bcpl.net> wrote in message
news:a7qll4$1870$1 digitaldaemon.com...
 I'm also getting an error during compile ('array.length' is not an lvalue)
 with the following:
   int[] array;

   array[array.length++] = 0;
   array[array.length++] = 1;
   array[array.length] = 2;

I disabled setting array.length for operators other than assignment because
it reallocates the array, which is an expensive operation. Adding array
elements one by one, incrementing the array length each time, will have
terrible runtime performance.

The way to do it is to preallocate your best guess as to what you'll need,
stuff the array elements, and then do an assignment to set the final size.
If, as you're stuffing array elements, you run out of length, doubling the
existing array length is a good strategy.

Mar 26 2002

"Gary" <gedumer bcpl.net> writes:

Walter <walter digitalmars.com> wrote in message
news:a7r3am$1gcu$1 digitaldaemon.com...
 "Gary" <gedumer bcpl.net> wrote in message
 news:a7qll4$1870$1 digitaldaemon.com...
 I'm also getting an error during compile ('array.length' is not an


lvalue)
 with the following:
   int[] array;

   array[array.length++] = 0;
   array[array.length++] = 1;
   array[array.length] = 2;

 I disabled setting array.length for operators other than assignment

because
 it reallocates the array, which is an expensive operation. Adding array
 elements one by one, incrementing the array length each time, will have
 terrible runtime performance.

 The way to do it is to preallocate your best guess as to what you'll need,
 stuff the array elements, and then do an assignment to set the final size.
 If, as you're stuffing array elements, you run out of length, doubling the
 existing array length is a good strategy.

Exactly... how would you do that?

Mar 26 2002

"Walter" <walter digitalmars.com> writes:

"Gary" <gedumer bcpl.net> wrote in message
news:a7r5iq$1hg6$1 digitaldaemon.com...
 The way to do it is to preallocate your best guess as to what you'll


need,
 stuff the array elements, and then do an assignment to set the final


size.
 If, as you're stuffing array elements, you run out of length, doubling


the
 existing array length is a good strategy.

 Exactly... how would you do that?

array.length = 100;        // guess
for (i = 0; 1; i++)
{    c = getinput();
      if (!c)
        break;
      if (i == array.length)
        array.length = array.length * 2;
      array[i] = c;
}
array.length = i;

Picking a good initial guess is an art, but you usually can pick a value
covering 99% of the cases. For example, suppose you are gathering user input
from the console - it's unlikely to be longer than 80.

Mar 26 2002

"Gary" <gedumer bcpl.net> writes:

Walter <walter digitalmars.com> wrote in message
news:a7r7ok$1ing$1 digitaldaemon.com...
 "Gary" <gedumer bcpl.net> wrote in message
 news:a7r5iq$1hg6$1 digitaldaemon.com...
 The way to do it is to preallocate your best guess as to what you'll


 need,
 stuff the array elements, and then do an assignment to set the final


 size.
 If, as you're stuffing array elements, you run out of length, doubling


 the
 existing array length is a good strategy.

 Exactly... how would you do that?

 array.length = 100;        // guess
 for (i = 0; 1; i++)
 {    c = getinput();
       if (!c)
         break;
       if (i == array.length)
         array.length = array.length * 2;
       array[i] = c;
 }
 array.length = i;

 Picking a good initial guess is an art, but you usually can pick a value
 covering 99% of the cases. For example, suppose you are gathering user

input
 from the console - it's unlikely to be longer than 80.

WOW!!! That's a far cry from the example in the docs... which is what I was
trying to follow. I LIKE IT:)

Thanks... Gary.

Mar 26 2002

"Walter" <walter digitalmars.com> writes:

"Gary" <gedumer bcpl.net> wrote in message
news:a7r8b3$1j12$1 digitaldaemon.com...
 WOW!!! That's a far cry from the example in the docs... which is what I

was
 trying to follow. I LIKE IT:)

Looks like I should amend the docs <g>.

Mar 26 2002

Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:

Walter wrote:

 Picking a good initial guess is an art, but you usually can pick a value
 covering 99% of the cases. For example, suppose you are gathering user input
 from the console - it's unlikely to be longer than 80.

How about some sort of array index syntax that automatically doubles the array
length if the index is beyond the length?  Ok, I know the syntax I have below is
terrible, but what if you could write something like:

    array.length = 100;    // guess
    for(i=0; 1; i++)
    {   c = getinput();
        if(!c)
            break;
        array.autoextend[i] = c; // if i >= array.length, doubles array.length
automatically
    }
    array.length = i;

This doesn't add any code to the generated output (since we'd have to do the
test anyhow), but something like this would allow for a MUCH cleaneer syntax.

NOTE: I'm not suggesting that we automatically extend on ALL index
operations...only on specially marked ones.  Also, you could, potentially, allow
an argument on the autoextend to tell the compiler by what factor to increase
the length:

    array.autoextend(1.2)[i] ...    // float argument, autoextends by 20%
    array.autoextend(3)[] ...      // int argument, autoextends by tripling
length

--
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.[ (a version.of(English).(precise.more)) is(possible) ]
?[ you want.to(help(develop(it))) ]

Mar 27 2002

Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:

     array.autoextend(3)[] ...      // int argument, autoextends by tripling
 length

Oops, meant to type
    array.autoextend(3)[i]

--
The Villagers are Online! villagersonline.com

.[ (the fox.(quick,brown)) jumped.over(the dog.lazy) ]
.[ (a version.of(English).(precise.more)) is(possible) ]
?[ you want.to(help(develop(it))) ]

Mar 27 2002

"OddesE" <OddesE_XYZ hotmail.com> writes:

"Russ Lewis" <spamhole-2001-07-16 deming-os.org> wrote in message
news:3CA1E868.4BF36E49 deming-os.org...
     array.autoextend(3)[] ...      // int argument, autoextends by


tripling
 length

 Oops, meant to type
     array.autoextend(3)[i]

 --
 The Villagers are Online! villagersonline.com

 .[ (the fox.(quick,brown)) jumped.over(the dog.lazy) ]
 .[ (a version.of(English).(precise.more)) is(possible) ]
 ?[ you want.to(help(develop(it))) ]

Don't push your luck... :)


--
Stijn
OddesE_XYZ hotmail.com
http://OddesE.cjb.net
__________________________________________
Remove _XYZ from my address when replying by mail

Mar 27 2002

"Gary" <gedumer bcpl.net> writes:

Also... when do you expect string comparison to be incorporated?

Walter <walter digitalmars.com> wrote in message
news:a7r3am$1gcu$1 digitaldaemon.com...
 "Gary" <gedumer bcpl.net> wrote in message
 news:a7qll4$1870$1 digitaldaemon.com...
 I'm also getting an error during compile ('array.length' is not an


lvalue)
 with the following:
   int[] array;

   array[array.length++] = 0;
   array[array.length++] = 1;
   array[array.length] = 2;

 I disabled setting array.length for operators other than assignment

because
 it reallocates the array, which is an expensive operation. Adding array
 elements one by one, incrementing the array length each time, will have
 terrible runtime performance.

 The way to do it is to preallocate your best guess as to what you'll need,
 stuff the array elements, and then do an assignment to set the final size.
 If, as you're stuffing array elements, you run out of length, doubling the
 existing array length is a good strategy.

Mar 26 2002

"Pavel Minayev" <evilone omen.ru> writes:

"Walter" <walter digitalmars.com> wrote in message
news:a7r3am$1gcu$1 digitaldaemon.com...

 I disabled setting array.length for operators other than assignment

because
 it reallocates the array, which is an expensive operation. Adding array
 elements one by one, incrementing the array length each time, will have
 terrible runtime performance.

You're probably right... but what about -- and -=? They sound like
a replacement for pop_back() of STL containers - a thing that is
of common use. Currently, I have to use

    s.length = s.length - 1;

Why not

    s.length--;

?

Mar 26 2002

"Walter" <walter digitalmars.com> writes:

"Pavel Minayev" <evilone omen.ru> wrote in message
news:a7rirf$1ofi$1 digitaldaemon.com...
 "Walter" <walter digitalmars.com> wrote in message
 news:a7r3am$1gcu$1 digitaldaemon.com...
 I disabled setting array.length for operators other than assignment

 because
 it reallocates the array, which is an expensive operation. Adding array
 elements one by one, incrementing the array length each time, will have
 terrible runtime performance.

 You're probably right... but what about -- and -=? They sound like
 a replacement for pop_back() of STL containers - a thing that is
 of common use. Currently, I have to use
     s.length = s.length - 1;
 Why not
     s.length--;
 ?

Because then I'd be spending my life explaining why ++ is not implemented
but -- is ?? <g>

Mar 26 2002

"Pavel Minayev" <evilone omen.ru> writes:

"Walter" <walter digitalmars.com> wrote in message
news:a7rq5d$1s0b$3 digitaldaemon.com...

 Because then I'd be spending my life explaining why ++ is not implemented
 but -- is ?? <g>

Then, implement ++ as if a new element with default value of desired type
is added. That is, for int[], ++ adds -, for float[] it will be NAN etc...
the code would be essentially the same as for ~=.

Mar 27 2002

"Walter" <walter digitalmars.com> writes:

"Pavel Minayev" <evilone omen.ru> wrote in message
news:a7sde6$26vb$1 digitaldaemon.com...
 "Walter" <walter digitalmars.com> wrote in message
 news:a7rq5d$1s0b$3 digitaldaemon.com...

 Because then I'd be spending my life explaining why ++ is not


implemented
 but -- is ?? <g>

 Then, implement ++ as if a new element with default value of desired type
 is added. That is, for int[], ++ adds -, for float[] it will be NAN etc...
 the code would be essentially the same as for ~=.

That would work, but then I'm back to the original point that code that uses
++ on the .length most likely has a severe performance problem, so it's
discouraged by not supporting ++.

Mar 29 2002

"Pavel Minayev" <evilone omen.ru> writes:

"Walter" <walter digitalmars.com> wrote in message
news:a82km4$2m2l$2 digitaldaemon.com...

 Then, implement ++ as if a new element with default value of desired


type
 is added. That is, for int[], ++ adds -, for float[] it will be NAN


etc...
 the code would be essentially the same as for ~=.

 That would work, but then I'm back to the original point that code that

uses
 ++ on the .length most likely has a severe performance problem, so it's
 discouraged by not supporting ++.

It wouldn't be slower than ~=, right? And ~= is there...

Mar 29 2002

"Walter" <walter digitalmars.com> writes:

"Pavel Minayev" <evilone omen.ru> wrote in message
news:a82n7g$oq9$1 digitaldaemon.com...
 "Walter" <walter digitalmars.com> wrote in message
 news:a82km4$2m2l$2 digitaldaemon.com...
 That would work, but then I'm back to the original point that code that

 uses
 ++ on the .length most likely has a severe performance problem, so it's
 discouraged by not supporting ++.

 It wouldn't be slower than ~=, right? And ~= is there...

Yes, but ~= is useful for concatenating strings with more than one entry. ++
by definition only adds one, and so is the worst case solution :-(

Mar 29 2002

"Pavel Minayev" <evilone omen.ru> writes:

"Walter" <walter digitalmars.com> wrote in message
news:a82sab$2fjh$1 digitaldaemon.com...

 Yes, but ~= is useful for concatenating strings with more than one entry.

++
 by definition only adds one, and so is the worst case solution :-(

I often use ~= to build arrays element-by-element:

    char[] token;
    ...
    do
    {
        token ~= c;
        in.read(c);
    } while (isalpha(c));

The same "worst" case. I thought arrays try to compensate it by
allocating memory in blocks?

Mar 29 2002

"Walter" <walter digitalmars.com> writes:

"Pavel Minayev" <evilone omen.ru> wrote in message
news:a83g36$1sns$1 digitaldaemon.com...
 I often use ~= to build arrays element-by-element:
     char[] token;
     ...
     do
     {
         token ~= c;
         in.read(c);
     } while (isalpha(c));

 The same "worst" case. I thought arrays try to compensate it by
 allocating memory in blocks?

That turned out to have problems implementing it. The trouble was if someone
pointed to a slice adjacent to it at a higher memory address.

Apr 07 2002

"Pavel Minayev" <evilone omen.ru> writes:

"Walter" <walter digitalmars.com> wrote in message
news:a8p4l7$105m$1 digitaldaemon.com...

 "Pavel Minayev" <evilone omen.ru> wrote in message
 news:a83g36$1sns$1 digitaldaemon.com...
 I often use ~= to build arrays element-by-element:
     char[] token;
     ...
     do
     {
         token ~= c;
         in.read(c);
     } while (isalpha(c));

 The same "worst" case. I thought arrays try to compensate it by
 allocating memory in blocks?

 That turned out to have problems implementing it. The trouble was if

someone
 pointed to a slice adjacent to it at a higher memory address.

I can't understand... what do you mean by "adjancent slice"?

Apr 07 2002

"Walter" <walter digitalmars.com> writes:

"Pavel Minayev" <evilone omen.ru> wrote in message
news:a8pask$1d5t$1 digitaldaemon.com...
 "Walter" <walter digitalmars.com> wrote in message
 news:a8p4l7$105m$1 digitaldaemon.com...

 "Pavel Minayev" <evilone omen.ru> wrote in message
 news:a83g36$1sns$1 digitaldaemon.com...
 I often use ~= to build arrays element-by-element:
     char[] token;
     ...
     do
     {
         token ~= c;
         in.read(c);
     } while (isalpha(c));

 The same "worst" case. I thought arrays try to compensate it by
 allocating memory in blocks?

 That turned out to have problems implementing it. The trouble was if

 someone
 pointed to a slice adjacent to it at a higher memory address.

 I can't understand... what do you mean by "adjancent slice"?

    char[] a = new char[10];
    char[] b = a[5..10];
    a.length = 5;
    a.length = 10;

Oops! I just overwrote b!

Apr 07 2002

"Pavel Minayev" <evilone omen.ru> writes:

"Walter" <walter digitalmars.com> wrote in message
news:a8r7up$2nc$1 digitaldaemon.com...

     char[] a = new char[10];
     char[] b = a[5..10];
     a.length = 5;
     a.length = 10;

 Oops! I just overwrote b!

Hm... I thought that, when length increases, the memory is reallocated!

Apr 08 2002

"Walter" <walter digitalmars.com> writes:

"Pavel Minayev" <evilone omen.ru> wrote in message
news:a8rnff$14to$1 digitaldaemon.com...
 "Walter" <walter digitalmars.com> wrote in message
 news:a8r7up$2nc$1 digitaldaemon.com...

     char[] a = new char[10];
     char[] b = a[5..10];
     a.length = 5;
     a.length = 10;
 Oops! I just overwrote b!

 Hm... I thought that, when length increases, the memory is reallocated!

Yes, and it must be because of that scenario above.

Apr 12 2002

"Sean L. Palmer" <spalmer iname.com> writes:

Why not just double the darray's allocated space when array.length++ exceeds
the allocated space?  Oh, because you're only storing the length, assuming
the allocated size == the length, always.

Think of it like a std::vector<>::push_back().  Yeah it's inefficient but
sometimes it's the most elegant way to code an algorithm, and not everybody
is always primarily concerned with speed.  Think college D courses.  ;)

Sean

"Walter" <walter digitalmars.com> wrote in message
news:a7r3am$1gcu$1 digitaldaemon.com...
 "Gary" <gedumer bcpl.net> wrote in message
 news:a7qll4$1870$1 digitaldaemon.com...
 I'm also getting an error during compile ('array.length' is not an


lvalue)
 with the following:
   int[] array;

   array[array.length++] = 0;
   array[array.length++] = 1;
   array[array.length] = 2;

 I disabled setting array.length for operators other than assignment

because
 it reallocates the array, which is an expensive operation. Adding array
 elements one by one, incrementing the array length each time, will have
 terrible runtime performance.

 The way to do it is to preallocate your best guess as to what you'll need,
 stuff the array elements, and then do an assignment to set the final size.
 If, as you're stuffing array elements, you run out of length, doubling the
 existing array length is a good strategy.

Mar 27 2002

"OddesE" <OddesE_XYZ hotmail.com> writes:

"Sean L. Palmer" <spalmer iname.com> wrote in message
news:a7s781$23gk$1 digitaldaemon.com...
 Why not just double the darray's allocated space when array.length++

exceeds
 the allocated space?  Oh, because you're only storing the length, assuming
 the allocated size == the length, always.

 Think of it like a std::vector<>::push_back().  Yeah it's inefficient but
 sometimes it's the most elegant way to code an algorithm, and not

everybody
 is always primarily concerned with speed.  Think college D courses.  ;)

 Sean


Delphi TList uses a Capacity property. Count is the exact number
of elements in the list, Capacity is the amount of allocated elements.
Capacity - Count = WastedSpace  :)



--
Stijn
OddesE_XYZ hotmail.com
http://OddesE.cjb.net
__________________________________________
Remove _XYZ from my address when replying by mail

Mar 27 2002

"OddesE" <OddesE_XYZ hotmail.com> writes:

"OddesE" <OddesE_XYZ hotmail.com> wrote in message
news:a7ti96$2qni$1 digitaldaemon.com...
 Capacity - Count = WastedSpace  :)

Delphi typo... :)
Should be:

Capacity - Count == WastedSpace

Mar 27 2002

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D - String Comparison and Dynamic Arrays?