1. "Forward" function declarations?
I need to do the "C" equivalent of a "forward" function declaration in
Euphoria. Can this be done?
2. Re: "Forward" function declarations?
----- Original Message -----
From: "Ted Fines" <fines at macalester.edu>
To: <EUforum at topica.com>
Sent: Thursday, February 08, 2001 7:45 AM
Subject: "Forward" function declarations?
> I need to do the "C" equivalent of a "forward" function declaration in
> Euphoria. Can this be done?
>
Not directly. A forward reference is illegal in Euphoria:
funcion foo(object x)
integer z
z=bar(x) --syntax error "bar" not defined
return z+2
end function
function bar(object y)
if atom(y) return -1 else return length(y)
end function
printf(1,"%d",foo({1,2,3}))
and there is no way to declare a routine before it is defined (as there is
in C). Instead Euphoria uses routine_id():
integer bar_ID --bar_ID must be defined before foo()
funcion foo(object x)
integer z
z=call_func(bar_ID,{x})
return z+2
end function
function bar(object y)
if atom(y) return -1 else return length(y)
end function
bar_ID=routine_id("bar") -- routine_id() must be used after bar()
printf(1,"%d",foo({1,2,3}))
Now this works as foo() can "see" bar_ID and bar_ID is assigned a value
before foo() is called.
-- Mike Nelson
3. Re: "Forward" function declarations?
On 8 Feb 2001, at 10:13, Michael Nelson wrote:
>
> ----- Original Message -----
> From: "Ted Fines" <fines at macalester.edu>
> To: <EUforum at topica.com>
> Sent: Thursday, February 08, 2001 7:45 AM
> Subject: "Forward" function declarations?
>
>
> > I need to do the "C" equivalent of a "forward" function declaration in
> > Euphoria. Can this be done?
> >
>
> Not directly. A forward reference is illegal in Euphoria:
>
> funcion foo(object x)
> integer z
> z=bar(x) --syntax error "bar" not defined
> return z+2
> end function
>
> function bar(object y)
> if atom(y) return -1 else return length(y)
> end function
>
> printf(1,"%d",foo({1,2,3}))
>
> and there is no way to declare a routine before it is defined (as there is
> in C). Instead Euphoria uses routine_id():
>
> integer bar_ID --bar_ID must be defined before foo()
>
> funcion foo(object x)
> integer z
> z=call_func(bar_ID,{x})
> return z+2
> end function
>
> function bar(object y)
> if atom(y) return -1 else return length(y)
> end function
>
> bar_ID=routine_id("bar") -- routine_id() must be used after bar()
>
> printf(1,"%d",foo({1,2,3}))
>
>
> Now this works as foo() can "see" bar_ID and bar_ID is assigned a value
> before foo() is called.
This is another example of where the interpreter can be made smarter: If the
procedure
hasn't been declared yet, look further into the code for it!! I have seen some
programs
wherein everything has been routine_id()'d, and all procedure and function calls
are to
the routine_id . The interpreter could be doing this as a default, and making
the order
of precedence irrelevant.
Kat
4. Re: "Forward" function declarations?
</snip>
constant
TRUE = 1,
FALSE = 0
sequence
types,
handles,
rps
global procedure add_function (object handle, integer rp)
integer pos
pos = find (handle, handles)
if pos then
types[pos] = TRUE -- It does return something
rps[pos] = rp
else
handles = append(handles, handle)
types = append(types, TRUE)
rps = append(rps, TRUE)
end if
end procedure
global procedure add_procedure (object handle, integer rp)
integer pos
pos = find (handle, handles)
if pos then
types[pos] = FALSE -- It does return something
rps[pos] = rp
else
handles = append(handles, handle)
types = append(types, FALSE)
rps = append(rps, FALSE)
end if
end procedure
global function call_routine (object handle, sequence arg)
integer pos
pos = find (handle, handles)
if pos then
if types[pos] then
return {TRUE, call_func (rps[pos], arg)}
else
call_proc (rps[pos], arg)
return {TRUE}
end if
else
return {FALSE}
end if
end function
<snip\>
I think Kat might have been refering to this.
Euman
----- Original Message -----
From: "Kat" <gertie at PELL.NET>
To: <EUforum at topica.com>
Sent: Thursday, February 08, 2001 13:34
Subject: Re: "Forward" function declarations?
> On 8 Feb 2001, at 10:13, Michael Nelson wrote:
>
> >
> > ----- Original Message -----
> > From: "Ted Fines" <fines at macalester.edu>
> > To: <EUforum at topica.com>
> > Sent: Thursday, February 08, 2001 7:45 AM
> > Subject: "Forward" function declarations?
> >
> >
> > > I need to do the "C" equivalent of a "forward" function declaration in
> > > Euphoria. Can this be done?
> > >
> >
> > Not directly. A forward reference is illegal in Euphoria:
> >
> > funcion foo(object x)
> > integer z
> > z=bar(x) --syntax error "bar" not defined
> > return z+2
> > end function
> >
> > function bar(object y)
> > if atom(y) return -1 else return length(y)
> > end function
> >
> > printf(1,"%d",foo({1,2,3}))
> >
> > and there is no way to declare a routine before it is defined (as there
is
> > in C). Instead Euphoria uses routine_id():
> >
> > integer bar_ID --bar_ID must be defined before foo()
> >
> > funcion foo(object x)
> > integer z
> > z=call_func(bar_ID,{x})
> > return z+2
> > end function
> >
> > function bar(object y)
> > if atom(y) return -1 else return length(y)
> > end function
> >
> > bar_ID=routine_id("bar") -- routine_id() must be used after bar()
> >
> > printf(1,"%d",foo({1,2,3}))
> >
> >
> > Now this works as foo() can "see" bar_ID and bar_ID is assigned a value
> > before foo() is called.
>
> This is another example of where the interpreter can be made smarter: If
the procedure
> hasn't been declared yet, look further into the code for it!! I have seen
some programs
> wherein everything has been routine_id()'d, and all procedure and function
calls are to
> the routine_id . The interpreter could be doing this as a default, and
making the order
> of precedence irrelevant.
>
> Kat
>
>
5. Re: "Forward" function declarations?
Hi Kat,
> This is another example of where the interpreter can be made smarter: If
the procedure
> hasn't been declared yet, look further into the code for it!!
RDS is aware of this idea and acknowledges that technically it is not all
that difficult to do, but I believe that RDS won't do it because it is
against their philosophy.
------
Derek Parnell
Melbourne, Australia
(Vote [1] The Cheshire Cat for Internet Mascot)
