dynamic FOR statement
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.
- 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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and this works:
function circle(R,N) =
[ each for (w = [0:round(360/N):359])
(w<90)? [[Rcos(w),Rsin(w)]]:
(w<180)? [[Rcos(w),Rsin(w)]]:
(w==180)?
[[Rcos(w),Rsin(w)],[Rcos(w)+1,Rsin(w)],[Rcos(w)+1,Rsin(w)+1],[Rcos(w),Rsin(w)+1]]:
(w<270)? [[Rcos(w),Rsin(w)]]:
[[Rcos(w),Rsin(w)]]
];
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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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Did you:
The above code requires the experimental “lc-else” to be enabled (else
clauses in list comprehensions).
and maybe the others, in Edit/Preferences/Features (in latest snapshot
version).
Admin - PM me if you need anything, or if I've done something stupid...
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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
$ Runsun Pan, PhD $ libs: doctest , faces ( git ), offline doc ( git ), runscad.py ( 2 , git ), synwrite ( 2 ); $ tips: hash ( 2 ), matrix ( 2 , 3 ), sweep ( 2 , 3 ), var ( 2 ), lerp , animation ( gif , prodVid , animlib ), precision ( 2 ), xl-control , type , rounded polygon , chfont , tailRecur ( 2, 3 ), isosphere ( 2 ), area , vol/center , RGB , CurvedImg , tests ( 2 ), text ; $ Apps: rollApp , blockscad , openjscad , on AWS ( pdf )
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runsun wrote
It seems that both Parkinbot and kintel's version produce 3 more points
than expected:
Maybe I missed something ?
$ Runsun Pan, PhD $ libs: doctest , faces ( git ), offline doc ( git ), runscad.py ( 2 , git ), synwrite ( 2 ); $ tips: hash ( 2 ), matrix ( 2 , 3 ), sweep ( 2 , 3 ), var ( 2 ), lerp , animation ( gif , prodVid , animlib ), precision ( 2 ), xl-control , type , rounded polygon , chfont , tailRecur ( 2, 3 ), isosphere ( 2 ), area , vol/center , RGB , CurvedImg , tests ( 2 ), text ; $ Apps: rollApp , blockscad , openjscad , on AWS ( pdf )
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Yea I did miss it. Apology for quick action.
$ Runsun Pan, PhD $ libs: doctest , faces ( git ), offline doc ( git ), runscad.py ( 2 , git ), synwrite ( 2 ); $ tips: hash ( 2 ), matrix ( 2 , 3 ), sweep ( 2 , 3 ), var ( 2 ), lerp , animation ( gif , prodVid , animlib ), precision ( 2 ), xl-control , type , rounded polygon , chfont , tailRecur ( 2, 3 ), isosphere ( 2 ), area , vol/center , RGB , CurvedImg , tests ( 2 ), text ; $ Apps: rollApp , blockscad , openjscad , on AWS ( pdf )
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You have to download a recent dev snapshot (and alter the prefs there) to be
able to use each and if/else in lc.
There is also a nice solution that works for elder versions of OpenSCAD not
supporting the new features:
function circle(R,N) =
Each([ for (w = [0:round(360/N):359])
(w<90)? [[Rcos(w),Rsin(w)]]:
(w<180)? [[Rcos(w),Rsin(w)]]:
(w==180)?
[[Rcos(w),Rsin(w)],[Rcos(w)+1,Rsin(w)],[Rcos(w)+1,Rsin(w)+1],[Rcos(w),Rsin(w)+1]]:
(w<270)? [[Rcos(w),Rsin(w)]]:
[[Rcos(w),Rsin(w)]]
]);
function Each(L) = [for(i=L, j=i) j];
Note: Each has not exactly the same semantics as each as it always
returns a list and expects a list of lists. While it works at a different
nesting level, it does what you want.
It can even be implemented to do away with the extra brackets, which turns
it into a "special case list flatterer":
function circle(R,N) =
EachSC([ for (w = [0:round(360/N):359])
(w<90)? [Rcos(w),Rsin(w)]:
(w<180)? [Rcos(w),Rsin(w)]:
(w==180)?
[[Rcos(w),Rsin(w)],[Rcos(w)+1,Rsin(w)],[Rcos(w)+1,Rsin(w)+1],[Rcos(w),Rsin(w)+1]]:
(w<270)? [Rcos(w),Rsin(w)]:
[Rcos(w),Rsin(w)]
]);
function EachSC(L) = [for(i=L, j=i) i[0][0]== undef?i:j];
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Are you sure this is what you want?
echo(EachSC([[2,3],1,[4,5],[[6,7],[8,9]]]));
echo(EachSC([1,[2,3],[4,5],[[6,7],[8,9]]]));
echo(EachSC([[[6,7],[8,9]],1,[2,3],[4,5]]));
//ECHO: [[2, 3], [2, 3], 1, [4, 5], [4, 5], [6, 7], [8, 9]]
//ECHO: [1, [2, 3], [2, 3], [4, 5], [4, 5], [6, 7], [8, 9]]
//ECHO: [[6, 7], [8, 9], 1, [2, 3], [2, 3], [4, 5], [4, 5]]
2016-11-13 10:10 GMT-02:00 Parkinbot rudolf@parkinbot.com:
You have to download a recent dev snapshot (and alter the prefs there) to
be
able to use each and if/else in lc.
There is also a nice solution that works for elder versions of OpenSCAD not
supporting the new features:
function circle(R,N) =
Each([ for (w = [0:round(360/N):359])
(w<90)? [[Rcos(w),Rsin(w)]]:
(w<180)? [[Rcos(w),Rsin(w)]]:
(w==180)?
[[Rcos(w),Rsin(w)],[Rcos(w)+1,Rsin(w)],[Rcos(w)+1,R
sin(w)+1],[Rcos(w),Rsin(w)+1]]:
(w<270)? [[R*cos(w),R*sin(w)]]:
[[R*cos(w),R*sin(w)]]
]);
function Each(L) = [for(i=L, j=i) j];
Note: Each has not exactly the same semantics as each as it always
returns a list and expects a list of lists. While it works at a different
nesting level, it does what you want.
It can even be implemented to do away with the extra brackets, which turns
it into a "special case list flatterer":
function circle(R,N) =
EachSC([ for (w = [0:round(360/N):359])
(w<90)? [Rcos(w),Rsin(w)]:
(w<180)? [Rcos(w),Rsin(w)]:
(w==180)?
[[Rcos(w),Rsin(w)],[Rcos(w)+1,Rsin(w)],[Rcos(w)+1,R
sin(w)+1],[Rcos(w),Rsin(w)+1]]:
(w<270)? [R*cos(w),R*sin(w)]:
[R*cos(w),R*sin(w)]
]);
function EachSC(L) = [for(i=L, j=i) i[0][0]== undef?i:j];
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Ronaldo, it was an answer to one of the questions the thread was started with
- and not a general purpose solution for replacing each to deal with
wildly nested structures.
Parkinbot wrote
It can even be implemented to do away with the extra brackets,
which turns it into a "special case list flatterer"
:
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2016-11-13 13:10 GMT-02:00 Parkinbot rudolf@parkinbot.com:
Ronaldo, it was an answer to one of the questions the thread was started
with
- and not a general purpose solution for replacing each to deal with
wildly nested structures.
I have understood that. However, I don't think, however, that repetitions
were intended.
function EachSC(L) = [for(i=L, j=i) i[0][0]== undef?i:j];
function EachSC2(L) = [for(i=L, j = (i[0][0]!= undef? i:[i])) j];
L = [1,[2,2],[3,3,3], [[4,4,4],[5,5,5]],[6]];
echo(EachSC=EachSC(L));
echo(EachSC2=EachSC2(L));
//ECHO: EachSC = [1, [2, 2], [2, 2], [3, 3, 3], [3, 3, 3], [3, 3, 3], [4,
4, 4], [5, 5, 5], [6]]
//ECHO: EachSC2 = [1, [2, 2], [3, 3, 3], [4, 4, 4], [5, 5, 5], [6]]
I installed the snapshot version and activated the options.
Now I have all the suggested improvements working.
Also interesting to see how people like parkinbot manage to do the same with
the standard version.
Thanks for helping me.
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Ronaldo, all your example data structures are not wellformed according to the
discussed semantics. You also wouldn't call polygon() with it, or get an
error, because you are not allowed to feed a structure that is not a vector
of 2D points.
Back to the initial question of Johan: In the release version of OpenSCAD it
is no so easy to return more than one list element per cycle in a for-loop
(unless you use a pattern employing a second loop variable plus some
filters). So, if you want to return more than one element within a specific
cycle, you might get the idea to pack those elements into a sub-list and
later use a function for unpacking. This is the pattern my code example
shows.
Say, the overall aim is to get a 2D point list for polygon(). Each()
expects all elements being packed into sublists forcing you to write all
those extra bracket pairs for all cases in the orginal for loop.
If you don't wanna do this for single 2D points, you can write a
/specialized function/ like EachSC() that will test for nested list
elements and flatten only them.
Rudolf
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Sorry, Rudolf. My examples were unfortunate and overshadow my main point. As
far I understand your proposal for Johan's question, the output of the
EachSC function for the the input list
[ [1,1], [2,2], [ [3,3], [4,4] ], [5,5] ]
should be
[ [1,1], [2,2], [3,3], [4,4] , [5,5] ]
However, its output is
[ [1, 1], [1, 1], [2, 2], [2, 2], [3, 3], [4, 4], [5, 5], [5, 5] ]
The function EachSC2 follows your concept and does what you intended.
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Ronaldo, finally I got your point. Thanks for debugging the code. Didn't
spend much time on it for testing.
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I just looked it up in my code base. I'm indeed using the following version,
which is more explicit, but clumsier.
function Each_(L) = Each([for(i=L) i[0][0]?i:[i]]);
function Each(L) = [for(i=L, j=i) j];
echo(Each_([ [1,1], [2,2], [ [3,3], [4,4] ], [5,5] ]));
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