[OpenSCAD] for loop implicid union.

[Rogier Wolff]

Hi,

I have this puzzle I'm making:
makepuzzle (pitch=35, theblock = bn, real=1)
{
rotate ([ 0, 0, 0]) beam (r=bs, height=bl);
rotate ([ 0,180, 0]) beam (r=bs, height=bl);
rotate ([ 0, 90, 90]) beam (r=bs, height=bl);
rotate ([ 0,-90,-90]) beam (r=bs, height=bl);
rotate ([ 90, 0, 90]) beam (r=bs, height=bl);
rotate ([-90, 0,-90]) beam (r=bs, height=bl);
}

where I would like to have the list-of-rotations available elsewhere.

So I'm going towards:

makepuzzle (pitch=35, theblock = bn, real=1)
for (i=[0:5])
rotate (lor[i]) beam (r=bs, height=bl);

(lor is the list-of-rotations).

but now the "makepuzzle" module has only one child because for does an
implicit union. And makepuzzle needs access to all the six
children....

IMHO this is why the "implicit" anything is not a good idea. In pascal
there is the "writeln" with the implicit newline. As a building block
you cannot make a "write" out of that, but the other way around you
can easily make a writeln out of "write".

Similarly here: If you want a union of your for loop you can easily
add the union in front, but the other way around is difficult. Or at
least not obvious how to do it for me.

Roger.

[nop head]

Yes its a major problem but it isn't just for loops. Any openscad module,
like translate(), etc, can only return one child, so it has to union its
results.

The only way to get more than one child is to have a list in braces
directly after the object with the children() statements. You can't even
pass them on because children() being a module only ever returns one node.

I believe there is work in progress to fix this.

Post by Rogier Wolff
Hi,
makepuzzle (pitch=35, theblock = bn, real=1)
{
rotate ([ 0, 0, 0]) beam (r=bs, height=bl);
rotate ([ 0,180, 0]) beam (r=bs, height=bl);
rotate ([ 0, 90, 90]) beam (r=bs, height=bl);
rotate ([ 0,-90,-90]) beam (r=bs, height=bl);
rotate ([ 90, 0, 90]) beam (r=bs, height=bl);
rotate ([-90, 0,-90]) beam (r=bs, height=bl);
}
where I would like to have the list-of-rotations available elsewhere.
makepuzzle (pitch=35, theblock = bn, real=1)
for (i=[0:5])
rotate (lor[i]) beam (r=bs, height=bl);
(lor is the list-of-rotations).
but now the "makepuzzle" module has only one child because for does an
implicit union. And makepuzzle needs access to all the six
children....
IMHO this is why the "implicit" anything is not a good idea. In pascal
there is the "writeln" with the implicit newline. As a building block
you cannot make a "write" out of that, but the other way around you
can easily make a writeln out of "write".
Similarly here: If you want a union of your for loop you can easily
add the union in front, but the other way around is difficult. Or at
least not obvious how to do it for me.
Roger.
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[Rogier Wolff]

Post by nop head
Yes its a major problem but it isn't just for loops. Any openscad module,
like translate(), etc, can only return one child, so it has to union its
results.

Post by Rogier Wolff
Hi,
makepuzzle (pitch=35, theblock = bn, real=1)
{
rotate ([ 0, 0, 0]) beam (r=bs, height=bl);
rotate ([ 0,180, 0]) beam (r=bs, height=bl);
rotate ([ 0, 90, 90]) beam (r=bs, height=bl);
rotate ([ 0,-90,-90]) beam (r=bs, height=bl);
rotate ([ 90, 0, 90]) beam (r=bs, height=bl);
rotate ([-90, 0,-90]) beam (r=bs, height=bl);
}

I have found a reasonably elegant solution to my problem:

I have now the "one beam" module do the rotations (and colors)

So.. I'd like to use a loop here, but can't.
makepuzzle (pitch=35, theblock = bn, real=1) {
onebeam (0);
onebeam (1);
onebeam (2);
onebeam (3);
onebeam (4);
onebeam (5);
}

I'm working on a design where the number of pieces is not six, so
that'll be annoying. But other than that... things are looking good.


For printing I need to rotate the stuff back to a fixed orientation
so while forward rotation is:
rotate (lor[num]);
(list-of-rotations).

the inverse is:
module rrotate (v)
{
rotate ([-v[0],0,0])
rotate ([0,-v[1],0])
rotate ([0,0,-v[2]])
children ();
}


Roger.

[MichaelAtOz]

Post by nop head
I believe there is work in progress to fix this.

May be a while <https://github.com/openscad/openscad/issues/350> , it needs
some neurons applied.



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