new skill rhino3d-scripts (#1705)

* resolve readme validate * Apply suggestions from code review Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> Co-authored-by: John Haugabook <johnhaugabook@gmail.com> * rhino3d-scripts: rm reference to deprecated VBScript --------- Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
2026-05-30 02:21:46 +00:00 · 2026-05-14 21:08:46 -04:00
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+# VBScript Quirks for RhinoScript
+
+Things that bite when writing `.rvb` / `.vbs` files and aren’t obvious to anyone whose mental model is C-family or Python.
+
+## Always Start With `Option Explicit`
+
+Without it, mistyping a variable name silently creates a new `Variant` set to `Empty`. Every `.rvb` file should begin:
+
+```vbscript
+Option Explicit
+```
+
+## No Block Scope
+
+All `Dim` declarations inside a `Sub`/`Function` are hoisted to the top. A `Dim` inside an `If` block is visible after the `If` ends. Loop counters survive the loop.
+
+## `Nothing` vs `Empty` vs `Null`
+
+| Sentinel | Test with | Meaning |
+|---|---|---|
+| `Empty` | `IsEmpty(x)` | `Dim`’d but never assigned |
+| `Null` | `IsNull(x)` | Explicit “no value” — what `Rhino.GetObject` returns on cancel |
+| `Nothing` | `x Is Nothing` | An **object** reference that points to nothing — only for `Set` variables |
+
+Wrong sentinel → silently false.
+
+## Parentheses Change Semantics
+
+```vbscript
+Foo a, b              ' Call a Sub or Function (return value discarded)
+Call Foo(a, b)        ' Call a Sub or Function (return value discarded)
+x = Foo(a, b)         ' Call a Function and capture the return
+Foo(a, b)             ' SYNTAX ERROR for multi-arg subs
+
+Foo(x)                ' Calls Foo passing x BY VALUE, even if Foo declares ByRef
+Foo x                 ' Honors Foo's ByRef declaration
+```
+
+If a Sub modifies its argument and your change isn’t taking effect — you wrapped the argument in parentheses.
+
+## `ByRef` Is the Default
+
+Unlike most languages, VBScript passes arguments **by reference by default**. Functions can mutate their callers’ variables. Be explicit:
+
+```vbscript
+Sub Increment(ByRef n)
+    n = n + 1
+End Sub
+```
+
+## Arrays Are 0-Based But Have `UBound`, Not `Length`
+
+```vbscript
+Dim arr(2)            ' Three elements: arr(0), arr(1), arr(2)
+For i = 0 To UBound(arr)
+    arr(i) = i * 10
+Next
+```
+
+`Dim arr(n)` creates `n+1` elements. `ReDim Preserve arr(newSize)` resizes (only the last dimension of a multi-dim array).
+
+## `Set` Is Required for Object Assignment
+
+```vbscript
+Set fso = CreateObject("Scripting.FileSystemObject")    ' correct
+fso = CreateObject("Scripting.FileSystemObject")        ' RUNTIME ERROR
+```
+
+Any time the right-hand side is an object (COM object, RegExp, Dictionary), you must use `Set`.
+
+## Error Handling Is Manual
+
+```vbscript
+On Error Resume Next
+Rhino.AddCircle Array(0,0,0), -1
+If Err.Number <> 0 Then
+    Rhino.Print "Failed: " & Err.Description
+    Err.Clear
+End If
+On Error GoTo 0           ' Restore normal error behavior
+```
+
+`On Error Resume Next` suppresses **all** errors until `On Error GoTo 0`. Forgetting to restore is a common bug.
+
+## Points Are 3-Element Arrays
+
+Rhino expects `Array(x, y, z)`. A 2-element array (`Array(x, y)`) raises a type-mismatch error.
+
+```vbscript
+Dim pt
+pt = Array(1.0, 2.0, 3.0)
+Rhino.AddPoint pt
+```
+
+## String Concatenation Uses `&`, Not `+`
+
+`+` on strings works only if **both** sides are strings. If one side is a number, `+` does numeric addition and throws a type-mismatch. Always use `&`:
+
+```vbscript
+Rhino.Print "Count: " & n
+```
+
+## `For Each` Needs a `Variant`
+
+```vbscript
+Dim item
+For Each item In someCollection
+    ' ...
+Next
+```
+
+The loop variable must be `Variant`. You cannot `Dim item As Long` (VBScript has no typed `Dim`).