Hello,

I tried to generate an array in a function using a for loop, but it does not
work.
What am I doing wrong.

I tried to do something like this:
The ct function generate a two dimensional vector.

function chamber_(r,rb,h,bt,bb,pc) = [
[0,0],
[for (i=[1:8]) ct(r,bti/16,0,r)],
[for (i=[1:8]) ct(rb,-bbi/16,-h-rb,0,1)],
[-h,0],
[for (i=[8:1]) ct(rb,bbi/16,-h-rb,0,1)],
[for (i=[8:1]) ct(r,bti/16,0,r)],
[0,0],
];

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You probably need to remove the [ ] around the "for" calls:

p = [
[ 0, 0 ],
for (a = [ 1 : 9 ]) [ a, a ],
[ 10, 10 ],
for (a = [ 9 : -1 : 1 ]) [ a, a ],
[ 0, 0 ]
];

echo(p);

Also please use the 3 value variant for ranges that decrement
the value, e.g. [ 9 : -1 : 1 ].

Due to backward compatibility, defining [8:1] will NOT produce
the expected order, which is also mentioned in the warning:

DEPRECATED: Using ranges of the form [begin:end] with begin value greater than the end value is deprecated.

ciao,
Torsten.

Hi Paul,

Thank you for the info.  

I am not at all certain what you are talking about because I do not know the language that OpenScad uses.  I am a BASIC and Fortran guy.

I do understand "For Loops" etc but I need a reference for this language and more I need to understand the algorithm being used.  I am accustomed to "Top Down algorythmic design."

----- Original Message -----

From: Torsten Paulmailto:Torsten.Paul@gmx.de

To: discuss@lists.openscad.orgmailto:discuss@lists.openscad.org

Sent: Saturday, February 13, 2016 3:50 PM

Subject: Re: [OpenSCAD] use of for loop in function

You probably need to remove the [ ] around the "for" calls:

p = [
[ 0, 0 ],
for (a = [ 1 : 9 ]) [ a, a ],
[ 10, 10 ],
for (a = [ 9 : -1 : 1 ]) [ a, a ],
[ 0, 0 ]
];

echo(p);

Also please use the 3 value variant for ranges that decrement
the value, e.g. [ 9 : -1 : 1 ].

Due to backward compatibility, defining [8:1] will NOT produce
the expected order, which is also mentioned in the warning:

DEPRECATED: Using ranges of the form [begin:end] with begin value greater than the end value is deprecated.

ciao,
Torsten.

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

Thanks for reacting Torsten,

I made the modificatinos you suggested but get an error indicated after the
for statement when I remove the [].

ERROR: Parser error in line 410: syntax error
ERROR: Compilation failed!

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I also tried this one:

function chamber_(r,rb,h,bt,bb,pc) = [
concat([0,0],
[for (i=[1:1:8]) ct(r,bti/16,0,r)],
[for (i=[1:1:8]) ct(rb,-bbi/16,-h-rb,0,1)],
[-h,0],
[for (i=[8:-1:1]) ct(rb,bbi/16,-h-rb,0,1)],
[for (i=[8:-1:1]) ct(r,bti/16,0,r)],
[0,0])
];

It compiles but gives:
WARNING: PolySet has degenerate polygons

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As soon as I combine the [0,0] with the for statement it requires [] around
the for statement to compile.

This
ECHO: [[0, 0], [[0, 0], [0, 0], [0, 0], [0, 0], [0, 0], [0, 0], [0, 0], [0,
0]]]

is the result from this:

echo( newchamber_(0,0,0,0,0,0));
function newchamber_(r,rb,h,bt,bb,pc) = [
[0,0],
[for (i=[1:1:8]) ct(r,i*bt/16,0,r)]
];

and this
ECHO: [[0, 0, [0, 0], [0, 0], [0, 0], [0, 0], [0, 0], [0, 0], [0, 0], [0,
0]]]

from this:
function newchamber_(r,rb,h,bt,bb,pc) = [
concat([0,0],
[for (i=[1:1:8]) ct(r,i*bt/16,0,r)])
];

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I decide to solve it in another way:

function drawroom(i,r,rb,h,bt,bb,pc) =
(i<= $fn/8)? ct(r,-bti/($fn/4),0,r):
(i<= 3$fn/8)? csl(r,rb,h,bt,bb, (i-$fn/8)/($fn/4)):
(i<= 4*$fn/8) ? ct(rb,-bb*(4*$fn/8-i)/($fn/4),-h-rb,0,1):
(i<= 5*$fn/8) ? ct(rb,bb*(5*$fn/8-i)/($fn/4),-h-rb,0,1):
(i<= 7*$fn/8) ? csr(r,rb,h,bt,bb, (7*$fn/8-i)/($fn/4)):
ct(r,bt*(8*$fn/8-i),0,r);

function newchamber_(r,rb,h,bt,bb,pc) = [
for (i=[0:1:$fn-1]) drawroom(i,r,rb,h,bt,bb,pc)
];

There are still some bugs, but it compiles and it draws.

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Ah, good to hear that openscad is evolving!

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