One more EDA programmer reply, here... Tcl is super easy to embed as a shell for users, either in the terminal window the application is launched from or in a GUI text window. No doubt Tcl's embedability and historical connections to EDA come from Ousterhout's authorship of the Magic layout editor.
Lately I've been trying to embed Ruby the same way, and while I've succeeded, the process has been painful. The "event loop" is a particular challenge. So as far as I can tell Tcl is still leading in this regard. Can anyone chime in about Lua? I've heard some positive anecdotes.
Wow, there are a lot more EDA programmers on HN than I'd expected, some of whom I even recognise by name.
On topic, it's probably easier to embed Lua than Tcl, though you may miss some of the libraries. The language is cleaner (in some sense). For an EDA application, the only real problem is what your customer is supposed to do with 20+ years of scripts that they've written that are specific to their flow :)
Lately I've been trying to embed Ruby the same way, and while I've succeeded, the process has been painful. The "event loop" is a particular challenge. So as far as I can tell Tcl is still leading in this regard. Can anyone chime in about Lua? I've heard some positive anecdotes.