Yes they are still called variable because they can take any value at run time but can only be assigned once. See https://doc.rust-lang.org/book/ch03-01-variables-and-mutability.html This is how I would code Adrian's problem, although I haven't needed such a construct myself yet. r_h = is_undef(a) ? let(h = F(b), r = G(h, b)) [r, h] : let(r = f(a), h = g(r, a)) [r, h]; r = r_h[0]; h = r_h[1]; Or a slightly more compact version but I think less readable: r_h = is_undef(a) ? let(h = F(b)) [G(h, b), h] : let(r = f(a)) [r, g(r, a)]; r = r_h[0]; h = r_h[1]; On Sun, 28 Apr 2019 at 06:09, <lar3ry@sasktel.net> wrote: > On 27 Apr 2019 at 22:21, nop head wrote: > > It isn't the notation it the fact that in maths you don't let x mean one > thing and then on the next line > > make it mean some else. > > Again reinforcing my happiness in using a program instead of math. > > > There are lots of programming languages where you > > can't mutate variables. > > And yet they are still called variables. Fascinating. > > -- > Magic trumps science for most people, > and wishful thinking drives a lot of decision-making. > - Joe Haldeman > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

I noticed that (at least) two people felt like the coding problem I noted was sufficiently interesting that they tried to implement it. There is no other language I know where this would even be an interesting problem---it would just be trivial. The fact that more than one person thought my coding problem was a sufficient challenge that it was worth doing I think demonstrates the issue with the language. But that's not why I'm posting. I'm posting because I finally completed my rounded_extrude module which made this possible: box = [[0,0], [0,50], [255,50], [255,0]]; rbox = roundcorners(box, curve="smooth", type="cut", all=4); difference(){ rounded_extrude(rbox, height=50, r1=2, r2=1, steps = 22, edge1="teardrop", self_intersection=false); translate([0,0,2]) rounded_extrude(pathoffset(rbox, r=-2, closed=true), height=48, r1=4, r2=-1,steps=22,extra2=1,self_intersection=false); } So I have a rounded box with a teardrop edge at the base, a rounded top edge, and a more rounded interior bottom edge. <http://forum.openscad.org/file/t2477/fbox1.png> -- Sent from: http://forum.openscad.org/

On 2019-05-03 11:58, adrianv wrote: > So I have a rounded box with a teardrop edge at the base, a rounded top > edge, and a more rounded interior bottom edge. > > <http://forum.openscad.org/file/t2477/fbox1.png> That's very, very nice (and clever)! But what is a "teardrop edge" precisely? Carsten Arnholm

I use an inverted truncated rotate_extruded teardrop on the bottom edges of my rounded objects so they don't need support when printing. I assume that is what a "teardrop edge" is. [image: handle.png] On Fri, 3 May 2019 at 12:05, <arnholm@arnholm.org> wrote: > On 2019-05-03 11:58, adrianv wrote: > > So I have a rounded box with a teardrop edge at the base, a rounded top > > edge, and a more rounded interior bottom edge. > > > > <http://forum.openscad.org/file/t2477/fbox1.png> > > That's very, very nice (and clever)! But what is a "teardrop edge" > precisely? > > Carsten Arnholm > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

I've been working through this sort of thing myself, and have been working up a series of basic modules which do rounded edged (and optionally bottomed) pockets so as to model projects for a hobby CNC. The problem of course is working up a reasonable definition of the shapes in terms of parameters --- I believe the field which covers this sort of thing is topology? Does anyone know of any good texts on this which might be approachable to a layman? William On Fri, May 3, 2019 at 7:11 AM nop head <nop.head@gmail.com> wrote: > I use an inverted truncated rotate_extruded teardrop on the bottom edges > of my rounded objects so they don't need support when printing. I assume > that is what a "teardrop edge" is. > > [image: handle.png] > > On Fri, 3 May 2019 at 12:05, <arnholm@arnholm.org> wrote: > >> On 2019-05-03 11:58, adrianv wrote: >> > So I have a rounded box with a teardrop edge at the base, a rounded top >> > edge, and a more rounded interior bottom edge. >> > >> > <http://forum.openscad.org/file/t2477/fbox1.png> >> >> That's very, very nice (and clever)! But what is a "teardrop edge" >> precisely? >> >> Carsten Arnholm >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

I don't think topology is what you mean. For example a doughnut and a teacup with a handle are topologically the same. On Fri, 3 May 2019 at 14:54, William Adams <will.adams@frycomm.com> wrote: > I've been working through this sort of thing myself, and have been working > up a series of basic modules which do rounded edged (and optionally > bottomed) pockets so as to model projects for a hobby CNC. > > The problem of course is working up a reasonable definition of the shapes > in terms of parameters --- I believe the field which covers this sort of > thing is topology? > > Does anyone know of any good texts on this which might be approachable to > a layman? > > William > > > On Fri, May 3, 2019 at 7:11 AM nop head <nop.head@gmail.com> wrote: > >> I use an inverted truncated rotate_extruded teardrop on the bottom edges >> of my rounded objects so they don't need support when printing. I assume >> that is what a "teardrop edge" is. >> >> [image: handle.png] >> >> On Fri, 3 May 2019 at 12:05, <arnholm@arnholm.org> wrote: >> >>> On 2019-05-03 11:58, adrianv wrote: >>> > So I have a rounded box with a teardrop edge at the base, a rounded top >>> > edge, and a more rounded interior bottom edge. >>> > >>> > <http://forum.openscad.org/file/t2477/fbox1.png> >>> >>> That's very, very nice (and clever)! But what is a "teardrop edge" >>> precisely? >>> >>> Carsten Arnholm >>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> Discuss@lists.openscad.org >>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

Okay. Discussion of a list of two-dimensional shapes, mathematical/programmatic techniques for dividing shapes into regions, and the possible shapes which one can use in such deconstruction. Suggested text/terminology, esp. a book suited to a layman. Eventually the project may work up to 3 dimensional shapes, but for now, trying to limit it to stacks of two-dimensional shapes cut into a three-dimensional stock. William On Fri, May 3, 2019 at 10:43 AM nop head <nop.head@gmail.com> wrote: > I don't think topology is what you mean. For example a doughnut and a > teacup with a handle are topologically the same. > > On Fri, 3 May 2019 at 14:54, William Adams <will.adams@frycomm.com> wrote: > >> I've been working through this sort of thing myself, and have been >> working up a series of basic modules which do rounded edged (and optionally >> bottomed) pockets so as to model projects for a hobby CNC. >> >> The problem of course is working up a reasonable definition of the shapes >> in terms of parameters --- I believe the field which covers this sort of >> thing is topology? >> >> Does anyone know of any good texts on this which might be approachable to >> a layman? >> >> William >> >> >> On Fri, May 3, 2019 at 7:11 AM nop head <nop.head@gmail.com> wrote: >> >>> I use an inverted truncated rotate_extruded teardrop on the bottom >>> edges of my rounded objects so they don't need support when printing. I >>> assume that is what a "teardrop edge" is. >>> >>> [image: handle.png] >>> >>> On Fri, 3 May 2019 at 12:05, <arnholm@arnholm.org> wrote: >>> >>>> On 2019-05-03 11:58, adrianv wrote: >>>> > So I have a rounded box with a teardrop edge at the base, a rounded >>>> top >>>> > edge, and a more rounded interior bottom edge. >>>> > >>>> > <http://forum.openscad.org/file/t2477/fbox1.png> >>>> >>>> That's very, very nice (and clever)! But what is a "teardrop edge" >>>> precisely? >>>> >>>> Carsten Arnholm >>>> >>>> _______________________________________________ >>>> OpenSCAD mailing list >>>> Discuss@lists.openscad.org >>>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> Discuss@lists.openscad.org >>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

I think the correct term is Constructional Solid Geometry https://en.wikipedia.org/wiki/Constructive_solid_geometry You might find books on that but they are probably more about theory than actually how to make specific shapes with it. On Fri, 3 May 2019 at 16:03, William Adams <will.adams@frycomm.com> wrote: > Okay. Discussion of a list of two-dimensional shapes, > mathematical/programmatic techniques for dividing shapes into regions, and > the possible shapes which one can use in such deconstruction. > > Suggested text/terminology, esp. a book suited to a layman. > > Eventually the project may work up to 3 dimensional shapes, but for now, > trying to limit it to stacks of two-dimensional shapes cut into a > three-dimensional stock. > > William > > On Fri, May 3, 2019 at 10:43 AM nop head <nop.head@gmail.com> wrote: > >> I don't think topology is what you mean. For example a doughnut and a >> teacup with a handle are topologically the same. >> >> On Fri, 3 May 2019 at 14:54, William Adams <will.adams@frycomm.com> >> wrote: >> >>> I've been working through this sort of thing myself, and have been >>> working up a series of basic modules which do rounded edged (and optionally >>> bottomed) pockets so as to model projects for a hobby CNC. >>> >>> The problem of course is working up a reasonable definition of the >>> shapes in terms of parameters --- I believe the field which covers this >>> sort of thing is topology? >>> >>> Does anyone know of any good texts on this which might be approachable >>> to a layman? >>> >>> William >>> >>> >>> On Fri, May 3, 2019 at 7:11 AM nop head <nop.head@gmail.com> wrote: >>> >>>> I use an inverted truncated rotate_extruded teardrop on the bottom >>>> edges of my rounded objects so they don't need support when printing. I >>>> assume that is what a "teardrop edge" is. >>>> >>>> [image: handle.png] >>>> >>>> On Fri, 3 May 2019 at 12:05, <arnholm@arnholm.org> wrote: >>>> >>>>> On 2019-05-03 11:58, adrianv wrote: >>>>> > So I have a rounded box with a teardrop edge at the base, a rounded >>>>> top >>>>> > edge, and a more rounded interior bottom edge. >>>>> > >>>>> > <http://forum.openscad.org/file/t2477/fbox1.png> >>>>> >>>>> That's very, very nice (and clever)! But what is a "teardrop edge" >>>>> precisely? >>>>> >>>>> Carsten Arnholm >>>>> >>>>> _______________________________________________ >>>>> OpenSCAD mailing list >>>>> Discuss@lists.openscad.org >>>>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>>>> >>>> _______________________________________________ >>>> OpenSCAD mailing list >>>> Discuss@lists.openscad.org >>>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> Discuss@lists.openscad.org >>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

Yes, what I meant by "teardrop" is an edge which combines 45 degrees of a circular arc with a bevel at 45 deg so that the edge can be 3d printed without support---with the bevel down there are no unsupported areas at lower than a 45 deg angle. William Adams-2 wrote > Okay. Discussion of a list of two-dimensional shapes, > mathematical/programmatic techniques for dividing shapes into regions, and > the possible shapes which one can use in such deconstruction. I really don't understand your question. When people talk of dividing 2d shapes into regions they usually mean triangulating the shape. But it sounds like you mean something else. Maybe you should give a specific example? -- Sent from: http://forum.openscad.org/

Okay, a quick survey of an encyclopedia / dictionary yielded: * 0 ** circle ** oval/ellipse (requires some sort of non-arc curve) *** egg-shaped (requires some sort of non-arc curve) ** annulus (one circle within another forming a ring) ** superellipse (see astroid below) * 1 ** cone with rounded end (arc) * 2 ** semicircle/circular segment (arc and a straight line) ** lens/vesical piscis (two convex curves) ** lune/crescent (one convex one concave curve) ** heart (two curves) ** tomoe (comma shape) --- requires non arc curves * 3 ** triangle *** equilateral *** isosceles *** scalene ** sector (two straight edges, one convex arc) ** two straight edges, one concave arc ** Deltoid curve (three concave arcs) ** Reuleaux triangle (three convex arcs) ** Arbelos (one convex, two concave arcs) * 4 ** square ** rectangle ** parallelogram ** rhombus ** trapezoid/trapezium ** kite ** astroid (four concave arcs) ** salinon (four semicircles) any obvious corrections or additions? Other suggestions? William On Fri, May 3, 2019 at 11:03 AM William Adams <will.adams@frycomm.com> wrote: > Okay. Discussion of a list of two-dimensional shapes, > mathematical/programmatic techniques for dividing shapes into regions, and > the possible shapes which one can use in such deconstruction. > > Suggested text/terminology, esp. a book suited to a layman. > > Eventually the project may work up to 3 dimensional shapes, but for now, > trying to limit it to stacks of two-dimensional shapes cut into a > three-dimensional stock. > > William > > On Fri, May 3, 2019 at 10:43 AM nop head <nop.head@gmail.com> wrote: > >> I don't think topology is what you mean. For example a doughnut and a >> teacup with a handle are topologically the same. >> >> On Fri, 3 May 2019 at 14:54, William Adams <will.adams@frycomm.com> >> wrote: >> >>> I've been working through this sort of thing myself, and have been >>> working up a series of basic modules which do rounded edged (and optionally >>> bottomed) pockets so as to model projects for a hobby CNC. >>> >>> The problem of course is working up a reasonable definition of the >>> shapes in terms of parameters --- I believe the field which covers this >>> sort of thing is topology? >>> >>> Does anyone know of any good texts on this which might be approachable >>> to a layman? >>> >>> William >>> >>> >>> On Fri, May 3, 2019 at 7:11 AM nop head <nop.head@gmail.com> wrote: >>> >>>> I use an inverted truncated rotate_extruded teardrop on the bottom >>>> edges of my rounded objects so they don't need support when printing. I >>>> assume that is what a "teardrop edge" is. >>>> >>>> [image: handle.png] >>>> >>>> On Fri, 3 May 2019 at 12:05, <arnholm@arnholm.org> wrote: >>>> >>>>> On 2019-05-03 11:58, adrianv wrote: >>>>> > So I have a rounded box with a teardrop edge at the base, a rounded >>>>> top >>>>> > edge, and a more rounded interior bottom edge. >>>>> > >>>>> > <http://forum.openscad.org/file/t2477/fbox1.png> >>>>> >>>>> That's very, very nice (and clever)! But what is a "teardrop edge" >>>>> precisely? >>>>> >>>>> Carsten Arnholm >>>>> >>>>> _______________________________________________ >>>>> OpenSCAD mailing list >>>>> Discuss@lists.openscad.org >>>>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>>>> >>>> _______________________________________________ >>>> OpenSCAD mailing list >>>> Discuss@lists.openscad.org >>>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>>> >>> _______________________________________________ >>> OpenSCAD mailing list >>> Discuss@lists.openscad.org >>> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >>> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >