A couple of weeks ago there was a discussion about
function parameters for modules. I linked to the
proposal Doug made some time ago.

I wanted to have that feature for quite some time
so I had a closer look at this. The result is at
https://github.com/openscad/openscad/pull/3077
which is a prototype implementation of function
literals.

This still needs work, specifically verifying that
the parser changes did not break any existing
behavior and verification that the scoping works
as defined.

Anyone interested in helping to get that ready
for merging?

ciao,
Torsten.

It looks nice. This is helpful when developing flexible modules and
functions, such as sort, filter, etc.

http://openhome.cc

Sent from: http://forum.openscad.org/

So getting the variable scoping working needed a little
bit more work than anticipated, but it should be ok now.
Function literals capture the static scope as proposed
in:
https://github.com/doug-moen/openscad2/blob/master/rfc/Functions.md

Example with a function returning a function object
and using both lexical/static scoping of variable 'a'
and dynamic scoping of variable '$a'.

module m2(f1, f2) {
a = 3;
$a = 30;
echo(f1 = f1(0.03), f2 = f2(0.07));
}

module m1(f) {
a = 2;
$a = 20;
add2 = function(x) function(y) x + y + a + $a;
m2(f, add2(0.2));
}

a = 1;
$a = 10;
add1 = function(x) function(y) x + y + a + $a;
m1(add1(0.1));

// ECHO: f1 = 31.13, f2 = 32.27

Or for a more visual example defining a simple plot()
module taking a function.

module plot(count, f) {
for (x = [0 : count - 1]) {
translate([x, 0, 0]) cube([1, 1, 1 + f(x / count)]);
}
}

func_sin = function(x) 10 * sin(360 * x) + 10;
func_cos = function(x) 10 * cos(360 * x) + 10;
func_pow = function(x) 10 * pow(abs(4 * (x - 0.5)), 2);

funcs = [
[func_sin,  0, "red"],
[func_cos, 20, "green"],
[func_pow, 40, "yellow"]
];

for (func = funcs)
color(func[2])
translate([0, func[1], 0])
plot(100, func[0]);

Binary downloads of the current state of this branch:

Linux: https://app.circleci.com/jobs/github/openscad/openscad/3622/artifacts
Win32: https://app.circleci.com/jobs/github/openscad/openscad/3624/artifacts
Win64: https://app.circleci.com/jobs/github/openscad/openscad/3623/artifacts

ciao,
Torsten.

Just to close this thread, function literals are
now available in snapshot versions > 2019-10-24.

The feature is marked experimental, so it needs
to be enabled Preferences -> Features.

ciao,
Torsten.

Good news. It will give libraries great improvement. Looking forward to use
this feature in the next release.

https://openhome.cc

Sent from: http://forum.openscad.org/

I wanted to clarify something.  What if I want to write some code to operate
on functions, so

function foo(func) = ....;

If I want to pass an existing function like sin or cos, or maybe a function,
myfunc, that I defined, do I have to go through the whole syntax of

foo(function(x) sin(x))

or

foo(function(x,y) myfunc(x,y))

in order to do this?  Or if I want to define a function variable to equal
an existing function, similarly do I need to use the full syntax:

func_var = function(x) sin(x);

when the right hand side refers to a function that already exists?

--
Sent from: http://forum.openscad.org/

Yes! Just try it out.

function foo(a, f) = f(a);
echo(foo(30, sin));

gives obviously a syntax error: "Ignoring unknown variable 'sin' ... "
while the following code does what you intended.

echo(foo(30, function(x) sin(x)));

Trying to redefine sin() by

sin = function(x) sin(x); 

in order to call

echo(foo(30, sin)); 

will detect a recursion. While the following typo will indeed brick OpenSCAD

sin = function(x) sin(); 
echo(sin(30)); 

--
Sent from: http://forum.openscad.org/