1. little question once again
Can anyone explain what "namespace" is? I've come across it a number of
times, but i'm so lost.
And here's a Q i've asked before, but the i wasn't satisfied with the
answers, so i'll give it another try: what is the term that unifies
"variables" and "constants" (in the same sense that "routines" unifies
"procedures" and "functions")?
In doubt and in the dark,
Lionel
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2. Re: little question once again
Constants & Variables - Value holders
Namespace - only one item may have the name temp.
You can have object temp or atom temp or procedure temp
among a few other options but you can't have them all at
once.
Namespace issues arise with different files but the same
overall program.
Assume I have a program that handles both text mode and
graphics mode. The color blue in Text mode is represented
with the number 1 but the color blue in True Color
graphics is a three color setting. {0, 0, 255}
You can have BLUE = 1 or BLUE = {0,0,255} but it can't
equal both. Umm, well actually it can.
I could have an include file called, mytext.e and another
called mygrafix.e I can use BLUE locally in both cases
without conflict. This is because of NameSpace.
---mytext.e
function BLUE()
return 1
end function
---------
---mygrafix.e
function BLUE()
return {0,0,255}
end function
---------
We start running into trouble again when we set routines
to global. This means they are available outside the file
they are in.
---included.e
function BLUE()
return 5
end function
---------
---program.ex
include included.e
print(1, BLUE()) --prints "5"
---------
--program2.ex
include mytext.e
include mygrafix.e
print(1, BLUE())-- Error BLUE hasn't been declared.
---------
In program2.ex you get an error. BLUE hasn't been declared.
But you know you declared it. Twice even. once in mygrafix.e
and once in mytext.e. Neither is global and therefore don't
exist in program2.ex
The real problem comes during routine_id(). with routine_id()
you can't rename the routine or routine_id() won't find it.
During binding the following occurs. Every variable and
routine name gets renamed from myvariable and myroutine to
Aa and Ab. Extremely meaningless names. This is done for
2 reasons. One reason is to remove conflicts that would occur
because of namespace. When you include a file it is complete
seperate from the other file. However when you bind or shroud
you bring those 2 files together as one big file. NOW,
As I said before. program2.ex will fail with an error.
When you bind progarm2.ex it would look something like.
-----------
function Aa()
return 1
end function
function Ab()
return {0,0,255}
end function
print(1, Ac())
-----------
This is how Euphoria currently handles the namespacing when making
seperate files of one program come together as one program file.
The problem arises in routine_id() because -clear_routines() is required
and would force routines to retain their names.
-----------
function BLUE()
return 1
end function
function BLUE()
return {0,0,255}
end function
print(1, BLUE())
-----------
The above code obviously shows the attempt to redifine BLUE()
Lucius L. Hilley III
lhilley at cdc.net lucius at ComputerCafeUSA.com
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----- Original Message -----
From: Lionel Wong <eljay98 at HOTMAIL.COM>
To: <EUPHORIA at LISTSERV.MUOHIO.EDU>
Sent: Friday, September 24, 1999 11:07 PM
Subject: little question once again
> ---------------------- Information from the mail
header -----------------------
> Sender: Euphoria Programming for MS-DOS
<EUPHORIA at LISTSERV.MUOHIO.EDU>
> Poster: Lionel Wong <eljay98 at HOTMAIL.COM>
> Subject: little question once again
> --------------------------------------------------------------------------
-----
>
> Can anyone explain what "namespace" is? I've come across it a number of
> times, but i'm so lost.
>
> And here's a Q i've asked before, but the i wasn't satisfied with the
> answers, so i'll give it another try: what is the term that unifies
> "variables" and "constants" (in the same sense that "routines" unifies
> "procedures" and "functions")?
>
> In doubt and in the dark,
> Lionel
>
> ______________________________________________________
> Get Your Private, Free Email at http://www.hotmail.com
>
3. Re: little question once again
Re Lionel's question for a term to unify constants & variables:
I would use the word "Values". ie a constant is a permanent value, and a
variable is a changeable one.
Tracy.
4. Re: little question once again
On Sat, 25 Sep 1999 03:07:06 GMT, Lionel Wong <eljay98 at HOTMAIL.COM> wrote:
>Can anyone explain what "namespace" is? I've come across it a number of
>times, but i'm so lost.
NAMESPACE defines the scope of the variables, functions, procedures and
etc. In C++ a NAME is assigned to a section of your program and the data
and routines in that section is only made visible ( in SCOPE ) to the rest
of the program when you use that assigned name to refer to the data and
routines in that NAMESPACE.
>"variables" and "constants" (in the same sense that "routines" unifies
>"procedures" and "functions")?
constants and variables are called VARIABLES
The word constant is just a modifier to tell the compiler that
a variable's value can NOT be changed by the program during run-time.
Bernie
5. Re: little question once again
Lionel,
Variables and constants are labeled data *containers*. In a sense
constants are just handicapped variables with a whimsical restriction
imposed on them at birth: they are incapable of change through their
entire lifespan.
As Bernie already suggested, correctly, namespace is the *scope* of
various labels: it defines their accessibility (visibility) within
program environment. jiri
6. Re: little question once again
> constants and variables are called VARIABLES
Unfortunately, Bernie, if a constant is a variable then it's not constant
anymore. And if a variable is a constant then it's not variable anymore.
I tried to think so before, but it's a paradox, cancelling itself in truth.
Computer terms are paradoxical puns. =)
Thx anyway,
Lionel.
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7. Re: little question once again
- Posted by Bernie Ryan <bwryan at PCOM.NET>
Sep 25, 1999
-
Last edited Sep 26, 1999
On Sun, 26 Sep 1999 02:18:04 GMT, Lionel Wong <eljay98 at HOTMAIL.COM> wrote:
>> constants and variables are called VARIABLES
>
>Unfortunately, Bernie, if a constant is a variable then it's not constant
>anymore. And if a variable is a constant then it's not variable anymore.
>
>I tried to think so before, but it's a paradox, cancelling itself in truth.
>Computer terms are paradoxical puns. =)
>
>Thx anyway,
>Lionel.
>
>______________________________________________________
>Get Your Private, Free Email at http://www.hotmail.com
Linonel
You still do not understand what I mean.
A variable is the name of the location for storing data in memory.
You can define a variable to contain a constant value.
You can define a variable to contain a changing value.
Both are called variables.
Bernie
8. Re: little question once again
Bernie,
You've got the right idea about what variables and constants *are*, but they
aren't both called variables. Their names are quite literal:
variable \Va"ri*a*ble\, n. 1. That which is variable; that which varies, or is
subject to change.
constant \Con"stant\, n. 1. That which is not subject to change; that which is
invariable.
I think 'values' or even 'data holders' is more accurate than 'variables' to
describe them.
Greg Phillips
Bernie Ryan wrote:
> On Sun, 26 Sep 1999 02:18:04 GMT, Lionel Wong <eljay98 at HOTMAIL.COM> wrote:
>
> >> constants and variables are called VARIABLES
> >
> >Unfortunately, Bernie, if a constant is a variable then it's not constant
> >anymore. And if a variable is a constant then it's not variable anymore.
> >
> >I tried to think so before, but it's a paradox, cancelling itself in truth.
> >Computer terms are paradoxical puns. =)
> >
> >Thx anyway,
> >Lionel.
> >
> >______________________________________________________
> >Get Your Private, Free Email at http://www.hotmail.com
>
> Linonel
> You still do not understand what I mean.
> A variable is the name of the location for storing data in memory.
> You can define a variable to contain a constant value.
> You can define a variable to contain a changing value.
> Both are called variables.
> Bernie
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9. Re: little question once again
- Posted by Irv Mullins <irv at ELLIJAY.COM>
Sep 25, 1999
-
Last edited Sep 26, 1999
On Sat, 25 Sep 1999, you wrote:
> > constants and variables are called VARIABLES
>
> Unfortunately, Bernie, if a constant is a variable then it's not constant
> anymore. And if a variable is a constant then it's not variable anymore.
But, a constant IS variable. It can only be varied by the programmer prior to
the run (or the compile)
example:
constant pi = 3.0 -- that's wrong, but I can change it!
Irv
10. Re: little question once again
>Subject: Re: little question once again
> Date: Sat, 25 Sep 1999 23:24:09 -0400
> From: Bernie Ryan <bwryan at PCOM.NET>
>
> On Sun, 26 Sep 1999 02:18:04 GMT, Lionel Wong <eljay98 at HOTMAIL.COM> wrote:
>
>>> constants and variables are called VARIABLES
>>
>>Unfortunately, Bernie, if a constant is a variable then it's not constant
>>anymore. And if a variable is a constant then it's not variable anymore.
>>
>>I tried to think so before, but it's a paradox, cancelling itself in
truth.
>>Computer terms are paradoxical puns. =)
>>
>>Thx anyway,
>>Lionel.
>>
>>______________________________________________________
>>Get Your Private, Free Email at http://www.hotmail.com
>
> Linonel
> You still do not understand what I mean.
> A variable is the name of the location for storing data in memory.
> You can define a variable to contain a constant value.
> You can define a variable to contain a changing value.
> Both are called variables.
> Bernie
I am a new person on this mail list(as will seem obvious by the fact that I
posted this message originally in the wrong place, because I have been a
digest only person up to now), but have written to Robert in the past on
this very subject. The important point about"variable" and "constant" is
that in Euphoria, a constant is a very special animal. It is forced to
global scope by definition, and by the requirement that it be found in the
main line of the program. I can only assume, that constants are only handled
once by the interpreter, put into a special non-dynamic area at the
beginning of the name table and never revisited except for reference. I
also, suspect that in the interpretation process, they are substituted
either on a parse pass or with the "literals" in a statement. Speaking of
that, I believe that "literal" may be a term that all of you have been
searching for. All atoms that are not written as variables are literals by
usage in many other languages. The logical treatment of all atoms as numbers
in Euphoria gets rid of a confusion found in most languages at the expense
of introducing a confusion in the minds of most people not working as
programmers. The treatment of constants is exactly like that of literals
within the language. It is merely a bow to the symbolic way in which humans
process information. That is why it "logically" belongs in a parsing pass of
a statement rather than in dynamic variable resolution.
On Sat, 25 Sep 1999 22:37:06 -0400, Irv Mullins <irv at ELLIJAY.COM> wrote:
>On Sat, 25 Sep 1999, you wrote:
>> > constants and variables are called VARIABLES
>>
>> Unfortunately, Bernie, if a constant is a variable then it's not constant
>> anymore. And if a variable is a constant then it's not variable anymore.
>
>But, a constant IS variable. It can only be varied by the programmer prior
to
>the run (or the compile)
>example:
>constant pi = 3.0 -- that's wrong, but I can change it!
>
>Irv
And the idea that a constant is a variable because it can be changed by the
programmer should be an obvious logical dead-end...anything can be changed
by the programmer...then the whole program is a variable by that thinking.
Logically, that is so, but a real stretch for this discussion.
Everett L.(Rett) Williams
rett at gvtc.com
Everett L.(Rett) Williams
rett at gvtc.com
11. Re: little question once again
On 9/25/99 10:37:06 PM, Irv Mullins said:
>On Sat, 25 Sep 1999, you wrote:
>> > constants and variables are called VARIABLES
>>
>> Unfortunately, Bernie, if a constant is a variable then it's not constant
>> anymore. And if a variable is a constant then it's not variable anymore.
>
>But, a constant IS variable. It can only be varied by the programmer prior to
>the run (or the compile)
>example:
>constant pi = 3.0 -- that's wrong, but I can change it!
>
>Irv
I'm not sure that is a valid line of reasoning in this context.
After all, I can change *anything* in my program before run
time; that doesn't mean I want to call every component of the
program a variable.
I've always assumed that the names we give to the pieces of a
program get their meaning from the way they behave when the
program is actually acting as a program, i.e. being executed.
Otherwise they are just characters in a text file, anyway.
Of course, I am just assuming that based on the way I've
always treated those 'pieces'. Is that incorrect?
Craig
---------------------------------------------------------------
We used to think that if we knew one, we knew two, because one
and one are two. We are finding that we must learn a great deal
more about `and'.
--Sir Arthur Eddington
12. Re: little question once again
On Sat, 25 Sep 1999 22:37:06 -0400, Irv Mullins <irv at ELLIJAY.COM> wrote:
>constant pi = 3.0 -- that's wrong, but I can change it!
>
>Irv
Irv
That is true in Euphoria because Euphoria doesn't have real constants.
In C or C++ when you try to change a constant's value you will get a
run-time error. In C++ you can only explicitly override the constant by
using the const_cast operator.
Bernie
13. Re: little question once again
On Sun, 26 Sep 1999, you wrote:
> On Sat, 25 Sep 1999 22:37:06 -0400, Irv Mullins <irv at ELLIJAY.COM> wrote:
> >constant pi = 3.0 -- that's wrong, but I can change it!
> >
> That is true in Euphoria because Euphoria doesn't have real constants.
Bzzt! Sorry, that's the wrong answer. Euphoria will halt with this error
message:
may not change the value of a constant
pi = 3
> In C or C++ when you try to change a constant's value you will get a
> run-time error. In C++ you can only explicitly override the constant by
> using the const_cast operator.
Bzzt! again. (sort of) The whole purpose of constants is that they cannot be
programatically changed. A C++ constant is just a variable that's "hard" to
change. Pascal (Borland flavor) lets you change the value of constants even
easier, but at least the documentation says to thinkof them as "initialized
variables".
Irv
14. Re: little question once again
On Sun, 26 Sep 1999, Everett Williams wrote:
> >Subject: Re: little question once again
> And the idea that a constant is a variable because it can be changed by the
> programmer should be an obvious logical dead-end...anything can be changed
> by the programmer...then the whole program is a variable by that thinking.
> Logically, that is so, but a real stretch for this discussion.
In some languages I can change the meaning of symbols such as <= , not , or +
Not so in Euphoria. I can't override the reserved words such as for, do, end,
either. I can override identifiers such as printf (if I wish to make my
program more confusing)
In fact, the only things I can change in my program (without breaking someone
else's work) are the flow of the logic, the value of constants and
literals, and the names of functions and procedures.
All these are lumped together under the term "identifiers", which also includes
such things as types, record field names, and even program / module /
unit names, in languages which offer those things.
Regards,
Irv
15. Re: little question once again
Does it really matter?
Mike Hurley
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16. Re: little question once again
Mike Hurley wrote:
>Does it really matter?
>
Whether we have a word for constants and variables, probably not...but what
does matter is that the handling of constants and variables in Euphoria is
key to the growth of the language. Mr. Hilley's discussion of namespaces
points to an issue that will control the future uses and growth of Euphoria.
Until we, the user community, get a way to easily control the use of
constants and variables in large multi-module, multi-include programs
cleanly and logically, Euphoria will be limited in scope far more than it's
sort-of interpreted status would impose. Euphoria appears to be fast enough
to accomplish most standard programming needs and allows access to
sufficient other resources such as compiled or assembled code to fill in
when necessary. Right now, it takes way too much effort to make multiple
includes of similar natures get along. Talvitie's problems where she can use
Neil OR Exotica, but not select the best of both are a good example.
As has been discussed before, some kind of prefixing would solve many of
these problems and would make the process that bind accomplishes explicit.
One way to accomplish this would be through named includes, the name
becoming the prefix for reference to all routines and variables in that
include that are global in scope. It would also become an internal tag for
the interpreter to use when distinguishing conflicts. Just seems too simple
and logical not to do.
Everett l.(Rett) Williams
rett at gvtc.com
17. Re: little question once again
- Posted by Irv Mullins <irv at ELLIJAY.COM>
Sep 26, 1999
-
Last edited Sep 27, 1999
On Sun, 26 Sep 1999, Everett l.(Rett) Williams wrote:
> what
> does matter is that the handling of constants and variables in Euphoria is
> key to the growth of the language. Mr. Hilley's discussion of namespaces
> points to an issue that will control the future uses and growth of Euphoria.
> Until we, the user community, get a way to easily control the use of
> constants and variables in large multi-module, multi-include programs
> cleanly and logically, Euphoria will be limited in scope far more than it's
> sort-of interpreted status would impose. Euphoria appears to be fast enough
> to accomplish most standard programming needs and allows access to
> sufficient other resources such as compiled or assembled code to fill in
> when necessary. Right now, it takes way too much effort to make multiple
> includes of similar natures get along. Talvitie's problems where she can use
> Neil OR Exotica, but not select the best of both are a good example.
>
> As has been discussed before, some kind of prefixing would solve many of
> these problems and would make the process that bind accomplishes explicit.
> One way to accomplish this would be through named includes, the name
> becoming the prefix for reference to all routines and variables in that
> include that are global in scope. It would also become an internal tag for
> the interpreter to use when distinguishing conflicts. Just seems too simple
> and logical not to do.
Rob has promised that the namespace problem will next on his list of
things to do. I have no idea how he will accomplish this, but I personally
prefer the method you suggest - using the include file name as the prefix, eg:
foo.position(3.5) bar.position(5,5) which leads to more of an object oriented
approach to building programs. Not a bad thing IMHO.
Regards,
Irv
18. Re: little question once again
- Posted by Everett Williams <rett at GVTC.COM>
Sep 26, 1999
-
Last edited Sep 27, 1999
On Sun, 26 Sep 1999 20:55:20 -0400, Irv Mullins <irv at ELLIJAY.COM> wrote:
Irv wrote:
>Rob has promised that the namespace problem will next on his list of
>things to do. I have no idea how he will accomplish this, but I personally
>prefer the method you suggest - using the include file name as the prefix,
eg:
>foo.position(3.5) bar.position(5,5) which leads to more of an object
oriented
>approach to building programs. Not a bad thing IMHO.
>
>Regards,
>Irv
Irv,
Thanks for the info and support. Only one minor quibble. I'm not sure that I
ever want to get to instantiation, methods, and all that other fun
associated with object-oriented programming. I would just like to allow this
beautiful little procedural language to take on just enough extensions to
allow clean and easy usage of pre-existing code and libraries. Objects are
like Lil' Abners schmoos(if any of you are old enough to remember those :);
they multiply everywhere, they are many times of completely unknown and
unknowable content, and they encourage laziness(in this case in
programming).
Everett L.(Rett) Williams
rett at gvtc.com
19. Re: little question once again
Hello,
Tracy Tees wrote:
>Re Lionel's question for a term to unify constants & variables:
>I would use the word "Values". ie a constant is a permanent value, and a
>variable is a changeable one.
>Tracy.
>
I call them "Named values" because a value can be:
5 or
79.32 or
{1, 2, 3}
as well as the the name given to such values.
-- Illustration code
sequence msg
msg = "Hello world"
puts (1, msg)
-- End Illustration code
In this example, in the call to puts(), "1" is a value
but "msg" is a named value. Does this make sense?
later,
Lewis Townsend
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20. Re: little question once again
On Mon, 27 Sep 1999, LT wrote:
> Hello,
>
> Tracy Tees wrote:
>
> >Re Lionel's question for a term to unify constants & variables:
> >I would use the word "Values". ie a constant is a permanent value, and a
> >variable is a changeable one.
> >Tracy.
> >
OK, I finally looked this up in some of my programming books.
Variables and constants are lumped together under the term "DATA"
(surprise!)
This explains BASIC's use of statements such as DATA 4,5,7
which are the equivalent of constants, since they are fixed at write time.
And obviously variables, once intiialized, are also data, which can change
during the run.
Procedures and functions are not data.
Operators are not data.
Literals are unnamed constants - so they may qualify as data, I dunno.
Irv
21. Re: little question once again
> >Unfortunately, Bernie, if a constant is a variable then it's not constant
> >anymore. And if a variable is a constant then it's not variable anymore.
> >
> >I tried to think so before, but it's a paradox, cancelling itself in
>truth.
> >Computer terms are paradoxical puns. =)
> >
> >Thx anyway,
> >Lionel.
> >
>
>Lionel
> You still do not understand what I mean.
> A variable is the name of the location for storing data in memory.
> You can define a variable to contain a constant value.
> You can define a variable to contain a changing value.
> Both are called variables.
>Bernie
I know exactly what you meant, Bernie. I hope you noticed the literal
meaning, however. The paradox, though being true, was also meant to be a
joke. Laugh, you guys.
Lionel.
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