1. Re: Implementing structures
Irv replied to my proposals:
>These seem more OO than what we have been discussing.
OO looks a lot like structures, although it's not the same thing. Not =
being able to actually change the syntax puts a certain crimp on what =
you can do.
>Looking thru some old Pascal code, I find structures used
>extensively. Everywhere, actually. Quite useful, and makes
>for cleaner code.
>An example converted to Euphorish:
>structure listbox
> coords location -- we're assuming type coords
> coords size -- is already defined as
> sequence caption -- a structure with elements
> atom maxlen -- x and y, type checked to be
> ....etc. -- within valid range for screen coords.
I hadn't included that part in my examples, but here's the equivalent, =
using the proposed syntax:
constant structure( "listbox" ) -- new type of structure
element( "location", "coords" ) -- already defined
element( "size", "coords" ) -- ditto
element( "caption", "sequence" ) -- gets type checking
element( "maxlen", "atom" ) -- ditto
... etc
Since we are passing the data type along with the element name, we know =
what test to perform during data checking.
The "structure in a structure" is where these calls get expensive.
=20
>>
>>assignments would be done in the normal way:
>>with listbox
>> location =3D {1,1}
>> size =3D {100,100}
>> caption =3D "My List"
>> maxlen =3D 25
>>end listbox
My examples might look like:
set( "listbox.location.x", 1 )
set( "listbox.location.y", 1 )
set( "listbox.size.x", 100 ) =20
set( "listbox.size.y", 100 )
set( "listbox.caption", "My List" )
set( "listbox.maxlen", 25 )
If you wanted to implement a "with" procedure, it could look like:
with( "listbox" )
set( ".location.x", 1 )
set( ".location.y", 1 )
set( ".size.x", 100 ) =20
set( ".size.y", 100 )
set( ".caption", "My List" )
set( ".maxlen", 25 )
The *is* possible to make the code do this:
set( "listbox.location", {1,1} )
set( "listbox.size", {100,100} ) =20
set( "listbox.caption", "My List" )
set( "listbox.maxlen", 25 )
or even:
with( "listbox" )
set( ".location", {1,1} )
set( ".size", {100,100} ) =20
set( ".caption", "My List" )
set( ".maxlen", 25 )
But it makes some implict assumptions about the structure ( x =3D =
element 1, y =3D 2, etc.). If you ever changed the order of your =
structure, the code would break. So I'm not sure I'm a fan of that =
option.
>>You could use the same names (location...etc) for
>>other gadgets:
>> messagebox:location =3D {12,16}
Yeah, you get that, too. Same reservations about the multiple =
assignment, though.
>>The difference would be you could refer to listbox as a unit
>>(like any sequence) but assignments would be type checked,
>>i.e. location could not be assigned 1, or "Here". and maxlen
>>couldn't be "Lou" or {2,1} (Oh,yeah: no more LOCATION =3D 1,
>>SIZE=3D2, constant declarations needed, either)
You get that under my proposed system - if you can stomach the syntax. =
Since the names are maintained by the element() function, you don't need =
to worry about them at all.
>>I am not at all sure this could be implemented in any way
>>other than a change to Euphoria itself. Hope I am wrong.
If you want to use something other than functions and procedures, better =
start working on a pre-processor.
>Saturday -- ok, maybe Sunday. Depends upon all sorts of
>things, including the barometric pressure...
Great! I'm holding my breath.
-- David Cuny
