This was precisely my latest surprise too: no sum vector over array. Can be done with recursion, but yuck! Can't write like so
Sum(v,i=0) = {(i=len(v))? 0: v[i]+sum(v,i+1)}
Because that only works for vector of scalars. If you have vector of vectors you need a new function like above, but replace 0 with [0,0,0], or whatever the equivalent appropiate neutral element for addition. Or you can write it the ugly way:
Sum(v,i=0) = {(i=len(v)-1)? v[i]: v[i]+sum(v,i+1)}
(Syntax may be slightly wrong!)
-------- Original message --------
From: Joymaker kb@sparklight.com
Date:03/02/2015 14:06 (GMT-05:00)
To: discuss@lists.openscad.org
Cc:
Subject: Re: [OpenSCAD] A = A + 1;
My question falls right into this theme. A few days ago I set out to write a
little function to compute the average of a vector. Thought everything would
be straightforward.
// average a vector
function avg(vec) {
sum = 0;
for (n=vec) sum = sum + n;
return sum / len(vec);
}
Surprise! This language doesn't have functions with curly braces, it has
functions with equal signs. Given that it has modules with curly braces,
this took me greatly by surprise. Now, as I read this thread, I see that the
issue goes much deeper than I realized.
So, please suggest to me how to write the avg function. PLEASE don't tell me
that recursion is the best approach; this feels about as pretty as using
pliers to do a screwdriver's job.
Suggestion on the side: I was surprised not to find sum() and avg() on the
list of built-in functions operating on vectors. I recommend adding them.
Surely they are trivial to implement!
Cheers,
Ken
This was precisely my latest surprise too: no sum vector over array. Can be done with recursion, but yuck! Can't write like so
Sum(v,i=0) = {(i=len(v))? 0: v[i]+sum(v,i+1)}
Because that only works for vector of scalars. If you have vector of vectors you need a new function like above, but replace 0 with [0,0,0], or whatever the equivalent appropiate neutral element for addition. Or you can write it the ugly way:
Sum(v,i=0) = {(i=len(v)-1)? v[i]: v[i]+sum(v,i+1)}
(Syntax may be slightly wrong!)
-------- Original message --------
From: Joymaker <kb@sparklight.com>
Date:03/02/2015 14:06 (GMT-05:00)
To: discuss@lists.openscad.org
Cc:
Subject: Re: [OpenSCAD] A = A + 1;
My question falls right into this theme. A few days ago I set out to write a
little function to compute the average of a vector. Thought everything would
be straightforward.
// average a vector
function avg(vec) {
sum = 0;
for (n=vec) sum = sum + n;
return sum / len(vec);
}
Surprise! This language doesn't have functions with curly braces, it has
functions with equal signs. Given that it has modules with curly braces,
this took me greatly by surprise. Now, as I read this thread, I see that the
issue goes much deeper than I realized.
So, please suggest to me how to write the avg function. PLEASE don't tell me
that recursion is the best approach; this feels about as pretty as using
pliers to do a screwdriver's job.
Suggestion on the side: I was surprised not to find sum() and avg() on the
list of built-in functions operating on vectors. I recommend adding them.
Surely they are trivial to implement!
Cheers,
Ken
