OpenEuphoria

RE: A question about certain language features

• Posted by Ed Davis <ed_davis2 at yahoo.com> Feb 12, 2002
• 527 views

> > 1) Variables can not be initialized when declared, but
> > rather, must be initialized via an assignment statement.
> > Based on other languages, this seems like one of those
> > convenience type issues.  Is there some programming
> > philosophy that says that an initialization in a declaration
> > is a 'bad thing'?  What is the 'bad thing'?  I also note
> > that standard Pascal does not allow variables to be
> > initialized when they are declared.
>
> There is good article by Travis Beaty about this point.
> Visit please:
> http://www.RapidEuphoria.com/hotnew.htm
> There is the link to that article in this html.

Hmmm.  I read the article, but I still don't understand why:

function foo()
  integer a
  a = someNastyComputation()
  -- lots of code that massages a snipped
  return a
end function

is ok, whereas:

function foo()
  integer a = someNastyComputation()
  -- lots of code that massages a snipped
  return a
end function

is 'dangerous'? (if it were allowed, which it is not)

> > 2) No support of call by reference.  I understand that call
> > by reference can lead to unexpected side-effects, but since
> > changing global variables in a subroutine seems to
> > essentially cause the same problem, I don't understand this
> > omission.
>
> No any side-effects here with the *globals*. If you'll
> reference to gobal name from inside subroutine, then you
> change just that variable. Private variable name override
> global and local names inside subroutine and exists
> only inside subroutine.

integer a, b

function foo()
    a = 5
    return 6
end function

a = 1
b = foo() + a

See what I mean?  Even though call by reference is not
allowed, you can still have unexpected side effects, because
global (e.g., not local to a subroutine) variables can be
modified inside a subroutine.

> > 3) No support for local constants.
>
> There *is* full support for local constants in Euphoria.
> Terms are: global - for a different files scope,
> local -- just for single file scope, private -- just for
> current subroutine scope.
> *Private* constants are not supported, becouse of *all*
> private variables exist just inside soubroutine.
> Local constants are very useful for cross-routine use
> inside the library file. Say, you have global functions in
> the include file. You can set *local* constants just for
> those global functions just inside single lib.
>
> See and try Local <--> Private <--> Global,
> thing looks just like to the real life.

I think we are not talking about the same thing.  I am
referring to the reference manual, which says, in section
2.4.1, under heading "constants":

"Constants may not be declared inside a subroutine."

Thanks for your reply!