I like the idea of this. Can you tell us the definition of the function: $fn
= r2sides4n(R))

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Yes it is here:
https://github.com/nophead/NopSCADlib/blob/master/utils/core/global.scad#L37

On Tue, 17 Sep 2019 at 15:22, lar3ry lar3ry@sasktel.net wrote:

Robin2 wrote

It seems to me that the main use of redefining modules is to extend
functionality somehow in a library, so the existing built-ins can behave
consistently in the context of the library with other functionality.

The argument that the name "cube" is sacrosanct appears every day on this
forum:  many people seem to think that the burden of learning a new command
is quite overwhelming.

I would say that the situation is not so clear.  There do not appears to be
very many good libraries, well documented, that you can easily find.  I'm
not aware of a lot of good libraries that duplicate each other
substantially---maybe just BOSL with parts of dotSCAD.  But in my efforts
to hunt for libraries I saw a lot of functionality duplicated many times by
different people, maybe not put out as a library, but code that does the
same class of basic things, written by each individual to support other
purposes, because sharing libraries seems to be, for some reason, a very
difficult thing.  And if you write a library for your own use there's little
reason to bother documenting it.

The lack of a really clear mechanism for distributing libraries has been one
problem.  It's pretty hard to find the various libraries that are scattered
on Thingiverse.  The general hostility of people on the forum to the use of
libraries is another factor that I think has discouraged the development of
a functional approach to libraries.

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quite overwhelming.

OpenScad is a tiny language and can be learned in its entirety in about a
day, which I did many years ago. Libraries are much larger things to learn,
and if I can write everything I use myself, why would I spend time learning
somebody else's library?

I think the reason why they don't gain the same traction as conventional
programming languages is most things are very easy to do in OpenSCAD with a
few lines of code, whereas most libraries for other languages are a lot
bigger and more complicated.

On Wed, 18 Sep 2019 at 00:06, adrianv avm4@cornell.edu wrote:

My original reason for wanting this feature is the Relativity library.
https://github.com/davidson16807/relativity.scad

Relativity extends the standard primitives cube, sphere, etc, with upward compatible new features: a system of property inheritance inspired by CSS.

But, because of the way OpenSCAD works, Relativity needs to invent new names for all of the primitives. So, cube becomes box, cylinder becomes rod, and so on.

So if you want to use Relativity in an existing project, you need to rewrite your code to replace cube with box and so on.

It would be better if Relativity could just add new features to cube, sphere and so on without requiring you to rewrite all of your code.

This would not be a problem in any modern programming language, because all modern languages support name spaces.

The underlying goal of many of the suggestions in my email was to provide tools for library writers, so that libraries can work better. And so that libraries can do things that currently require a change to the C++ core. We need a better library ecosystem. If you don't use libraries, then many of my suggested language changes won't help you.

Doug Moen.

On Tue, Sep 17, 2019, at 7:11 PM, adrianv wrote:

But you can redefine cube and sphere. They hide the originals but there
really isn't any need to call the originals as they don't do anything
special. You would have a problem redefining polygon, and polyhedron though
I think.

On Wed, 18 Sep 2019 at 00:46, Doug Moen doug@moens.org wrote:

On 9/17/19 6:28 PM, nop head wrote:

I wish we would quit repeating this like it's the whole truth.  This
type of talk derails discussions that might lead to a decent library
ecosystem.

Yes, it's "easy" to do many things quickly.  It's also very easy to end
up with a "library" that's not actually very reusable, or hopelessly
slow, or fails to handle edge cases, or fails to provide reasonable
validation/assertions (making it easy to have problems using it).

Making good, reusable, documented libraries is hard.  Both because of
the nature of the work, but also because there are very few great
examples of libraries for OpenSCAD.  There's little work to borrow from,
so users tend to fall into the same beginner traps and either call it
"good enough for today's project" or give up on OpenSCAD entirely.

I have talked to many people off-list who were discouraged by this
"OpenSCAD doesn't need libraries" talk and just gave up rather than
contributing.  I really wish the negativity around libraries and package
managers would stop.

nophead wrote

I did not find it so easy to learn OpenSCAD as apparently you did.  Dealing
with the immutability of variables, and the need to use tail recursions
instead of loops---these things are not obvious.  And without any code
examples (because there are no libraries to read) one is left rather adrift
in trying to figure this stuff out.

Did you not just recently post that you redesigned your code using a
different design philosophy of making everything from extruded 2d shapes and
got it to render much faster?  (Assuming I remembered that correctly) that
suggests to me that you are still learning how to use OpenSCAD.  Note that
knowing how to use the language is not just knowing its commands, but
understanding fully, deeply, how they interact, and the advantages and
disadvantages of different approaches for modeling the same thing.  I'm kind
of skeptical that there are many people who really understand the ins and
outs of polyhedron() within the first day of using OpenSCAD.  Indeed, there
may not be many such people at all.

The question "If I can write everything I use myself, why would Is spend
time learning somebody else's library?" is really bizarre to me.  I can, in
principle, write everything I do on the computer myself in assembly
language.  But would I want to do that?  Heck no!  It would take a lot
longer to do that than to learn the libraries.  And at least for me, the
effort of learning a library, or the 10 seconds it takes to check the
library manual to remember a parameter name, is much less than the effort
required to write the thing again from scratch.  And for me it tends to
produce code that is more maintainable.
Indeed, the question I would pose in general is: "If there is a library that
does it, why would I spend the time writing it myself??"

I think the reason they don't gain the same traction as conventional
programming languages is that a vocal population here on the forum thinks
they are unnecessary because the things thosepeoplewanttodo are easy.
And for some reason some of these people vocallyoppose* libraries instead
of just ignoring them.  That's what I find puzzling.  If someone is happy
with base OpenSCAD that person can be happy and go model something----and
ignore any libraries that are written.  Why are libraries so offensive to
people who aren't going to use them?

If you want to make just rectangular objects with sharp corners, then things
are in fact pretty easy.  But if you want to do things that are curved, with
rounded edges, not so much.  My first OpenSCAD design is 108 lines and my
second one is the same length.  My third one design is 357 lines of
OpenSCAD, and it wasan't "very easy" or what I would consider "a few lines
of code".  The modeling process was pretty painful and there were lots of
steps that were trial-and-error based, which I hate.  It also takes about 20
minutes to render, which was pretty annoying during design.  The desire to
make this sort of model easier is what lead me to search for libraries.

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On 9/17/19 7:21 PM, adrianv wrote:

This times 1000!  Nobody is going to make you use other people's
libraries, but there's no reason to discourage everyone else from
writing them. Please quit doing so!

adrianv wrote

It is also that the language needs further mechanisms to facilitate
libraries.
There is a basic mechanism, the libraries directory of OpenSCAD releases,
however as MCAD has shown it's development is hindered by (as Doug has
written just now) lack of " tools for library writers, so that libraries can
work better".
Then there can be a concept of 'std' libraries and external libraries. Once
there is better library support a 'std' library will be maintainable and
'best' practice can be developed. [I think tp's 'Functions literals / higher
order functions' will prove to be very helpful, add namespaces and probably
few other smaller pieces to support versioning, and it becomes workable]

There are, at least, two types of people here, those who subscribe to the
concept of standard libraries, and those who prefer to roll their own.
Personally I'm in both camps. Both types have explained their reasoning
here.
I have not detected hostility, and I don't think views of roll their own are
trying to discourage developments. Or that evangelicals should expect others
to see the light.

This type of discussion come up every year or two then fades away.

Instead of discussing libraries, I think the focus should be on "tools for
library writers" AND maintainers.
Then in conjunction developing 'best' practice guidelines on the criteria
code should have to be considered for formal inclusion in both a core
standard library [distributed in a release], or a 'recognised' external
library [that gets promoted on OpenSCAD web site, support with issues etc].

That's at least 3 phases and won't happen overnight.
I think namespaces would be a next logical step.

[I see there is now a bunch of replies I have yet to read, so obviously not
covered above]

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