bug report: max(), min() and norm()
While trying to implement some min()/max()/norm() related stuff I stumbled
over the following buggy semantics.
I implemented the expected semantics for primitive functions:
A = [
[2, 5, 3, 4],
[1, 2, 3, 4],
[2, 4, 5, 7],
];
// Max
echo(max(A)); // [2, 5, 3, 4] ???
echo(max(max(A))); // 5 ???
echo(Max(A)); // 7 expected
echo(Max(A, false)); // [5, 4,7] expected
echo(min(A)); // [2, 5, 3, 4] ???
echo(min(min(A))); // 2 ???
echo(Min(A)); // 1 expected
echo(Min(A, false)); // [2, 1, 2] expected
echo(norm(A)); // undef + warning ???
echo(Norm(A)); // [7.34847, 5.47723, 9.69536] expected
function Max(A, flat=true) =
let (m =
len(A[0])>1?
[for(i=[0:len(A)-1]) Max(A[i])]:
max(A) )
flat?max(m):m;
function Min(A, flat=true) =
let (m =
len(A[0])>1?
[for(i=[0:len(A)-1]) Min(A[i])]:
min(A) )
flat?min(m):m;
function Norm(A) =
let (m =
len(A[0])>1?
[for(i=[0:len(A)-1]) Norm(A[i])]:
norm(A) )
m;
--
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From the wiki, it is not designed for matrices.
max
Returns the maximum of the parameters. If a single vector is given as
parameter, returns the maximum element of that vector.
Parameters
max(n,n{,n}...)
max(vector)
Usage Example:
max(3.0,5.0)
max(8.0,3.0,4.0,5.0)
max([8,3,4,5])
Results:
5
8
8
min
Returns the minimum of the parameters. If a single vector is given as
parameter, returns the minimum element of that vector.
Parameters
min(n,n{,n}...)
min(vector)
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I would interpret it slightly differently.
I.e. I woud lexpect the max of A to be one of A's entries.
I.e. echo(max(A)); // [2, 4, 5, 7] because its the one whose sum is
the max.
I.e. a max of each entry in the array A determines which entry is the max.
Likewise for max(max(A)) I would expect to see 7
So min(A) would be [1,2,3,4]
min(min(A)) would be 1
Its just convention and as nophead points out - its not defined in the
language - yet :)
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@MichaelAtOz
Well, at least I would not expect it to give a false result, but a warning
and an undef.
@Neon22
actually this is, what I had expected. But in this case you run into these
problems:
- the client code using min/max has to know (and parse) the structure,
which is not always granted or desireable. - what will max/min do with nested Arrays of the form [.., [..., ],
...]?
So better give it a second argument with a default value.
I came over it, because I wanted to use it for bounding box calculations of
interpolated extrusion data, where the size of an object is not known in
advance.
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Parkinbot wrote
@MichaelAtOz
Well, at least I would not expect it to give a false result, but a warning
and an undef.
I agree, silent failure, which seems to be inherent in much of OpenSCAD, is
not one of its shining features.
It drove me nuts on occasion when I was starting to learn it.
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