Johan_s_examples.scad
http://forum.openscad.org/file/n19053/Johan_s_examples.scad

Hello

I try to make some simple examples for myself to have some easy to copy and
past starts for new objects. While doing that I like also to define some
solutions and tricks. But not all of them are working. Maybe someone has
some suggestions.

1. dynamic FOR statement
   What I sometimes miss is a While loop where the variable has a more dynamic
   delta than the fixed one in a for loop. This is a simple way I use to fix
   that:

Or in a function:

In fact what I want to make is this:

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Jon,

The "dynamic for statement" and, at least, some forms of "multiple vectors
in a function" are already possible with the snapshot version  extensions to
list comprehension
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/WIP#Overview  .

for (h=[ each [0:1:10], each [10:10:1000], each [1000:1:1010] ])

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You can do this:

for(r=[[0:1:10],[10:10:1000],[1000:1:1010]], h = r)
echo(h);

I.e. r iterates through a list of ranges and h iterates through each range.

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thanks!
Works excellent and the code is much more readable.

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In terms of multiple vectors in a function: Since most of your cases are the same, you could also simplify it like this:

function circle(R,N) =
[ for (w = [0:round(360/N):359])
if (w==180) each [[Rcos(w),Rsin(w)],
[Rcos(w)+1,Rsin(w)],
[Rcos(w)+1,Rsin(w)+1],
[Rcos(w),Rsin(w)+1]]
else [Rcos(w),Rsin(w)]
];

The above code requires the experimental “lc-else” to be enabled (else clauses in list comprehensions).

-Marius

Thanks for all these suggestions.

But I am sorry.
Syntax errors are reported when I use "each".
Do I have to install enhancements on the list comprehensions?
How do I do that and how do I activate them?

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It seems that both Parkinbot and kintel's version produce 3 more points than
expected:

echo( len( circle_Parkinbot( 10,6)) ); //==> 9
echo( len( circle_Parkinbot( 10,12)) ); //==> 15
echo( len( circle_Parkinbot( 10,36)) ); //==> 39

echo( len( circle_Kintel( 10,6)) ); //==> 9
echo( len( circle_Kintel( 10,12)) ); //==> 15
echo( len( circle_Kintel( 10,36)) ); //==> 39

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