modeling-app/docs/kcl-lang/types.md

title, excerpt, layout

title	excerpt	layout
Values and types	Documentation of the KCL language for the Zoo Design Studio.	manual

KCL defines the following types and keywords the language.

All these types can be nested in various forms where nesting applies. Like arrays can hold objects and vice versa.

Constant declaration

Constants are defined with a name and a value, like so:

myBool = false

Currently you cannot redeclare a constant.

Arrays

An array is defined with [] braces. What is inside the brackets can be of any type. For example, the following is completely valid:

myArray = ["thing", 2, false]

If you want to get a value from an array you can use the index like so: myArray[0].

Objects

An object is defined with {} braces. Here is an example object:

myObj = { a = 0, b = "thing" }

We support two different ways of getting properties from objects, you can call myObj.a or myObj["a"] both work.

ImportedGeometry

Using import you can import geometry defined using other CAD software. In KCL, these objects have type ImportedGeometry and can mostly be treated like any other solid (they can be rotated, scaled, etc.), although there is no access to their internal components. See the modules and imports docs for more detail on importing geometry.

Tags

Tags are used to give a name (tag) to a specific path.

TagDeclarator

The syntax for declaring a tag is $myTag you would use it in the following way:

startSketchOn(XZ)
  |> startProfile(at = origin)
  |> angledLine(angle = 0, length = 191.26, tag = $rectangleSegmentA001)
  |> angledLine(
       angle = segAng(rectangleSegmentA001) - 90,
       length = 196.99,
       tag = $rectangleSegmentB001,
     )
  |> angledLine(
       angle = segAng(rectangleSegmentA001),
       length = -segLen(rectangleSegmentA001),
       tag = $rectangleSegmentC001,
     )
  |> line(endAbsolute = [profileStartX(%), profileStartY(%)])
  |> close()

TagIdentifier

As per the example above you can use the tag identifier to get a reference to the tagged object. The syntax for this is myTag.

In the example above we use the tag identifier to get the angle of the segment segAng(rectangleSegmentA001).

Start

There is a special tag, START (with type Start, although under the cover, it's a string) for identifying the face of a solid which was the start of an extrusion (i.e., the surface which is extruded).

End

There is a special tag, END (with type End, although under the cover, it's a string) for identifying the face of a solid which was finishes an extrusion.

Tag Scope

Tags are scoped globally if in the root context meaning in this example you can use the tag rectangleSegmentA001 in any function or expression in the file.

However if the code was written like this:

fn rect(origin) {
  return startSketchOn(XZ)
    |> startProfile(at = origin)
    |> angledLine(angle = 0, length = 191.26, tag = $rectangleSegmentA001)
    |> angledLine(
         angle = segAng(rectangleSegmentA001) - 90,
         length = 196.99,
         tag = $rectangleSegmentB001,
       )
    |> angledLine(
         angle = segAng(rectangleSegmentA001),
         length = -segLen(rectangleSegmentA001),
         tag = $rectangleSegmentC001,
       )
    |> line(endAbsolute = [profileStartX(%), profileStartY(%)])
    |> close()
}

rect(origin = [0, 0])
rect(origin = [20, 0])

Those tags would only be available in the rect function and not globally.

However you likely want to use those tags somewhere outside the rect function.

Tags are accessible through the sketch group they are declared in. For example the following code works.

fn rect(origin) {
  return startSketchOn(XZ)
    |> startProfile(at = origin)
    |> angledLine(angle = 0, length = 191.26, tag = $rectangleSegmentA001)
    |> angledLine(
         angle = segAng(rectangleSegmentA001) - 90,
         length = 196.99,
         tag = $rectangleSegmentB001,
       )
    |> angledLine(
         angle = segAng(rectangleSegmentA001),
         length = -segLen(rectangleSegmentA001),
         tag = $rectangleSegmentC001,
       )
    |> line(endAbsolute = [profileStartX(%), profileStartY(%)])
    |> close()
}

rect(origin = [0, 0])
myRect = rect(origin = [20, 0])

myRect
  |> extrude(length = 10)
  |> fillet(radius = 0.5, tags = [myRect.tags.rectangleSegmentA001])

See how we use the tag rectangleSegmentA001 in the fillet function outside the rect function. This is because the rect function is returning the sketch group that contains the tags.

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If you find any issues using any of the above expressions or syntax, please file an issue with the ast label on the modeling-app repo.