[lispm]

>a programming language that treats symbols as a first-class concept is indeed a rare beast

JavaScript

> Only computer algebra systems really attempt this

There are a bunch of programming systems (incl. computer algebra systems) on top of Lisp, which use various types symbol expressions.

[dTal]

How does javascript qualify? x2 => ReferenceError: x is not defined, same as any other non symbolic language.

As for libraries - yes, there exist symbolic manipulation systems for Lisp - and Javascript, and Python (notably SymPy). But none of them integrate seamlessly with the language, because there's fundamental conflicts with the language's default evaluation model. You need to design something with that in mind from scratch, and doing it such a way as to make something elegant and composable and not a huge mess is really hard.

[lispm]

> How does javascript qualify?

It has symbols as a basic data type, slightly similar to Lisp.

> But none of them integrate seamlessly with the language, because there's fundamental conflicts with the language's default evaluation model

Lisp has symbols to implement these other evaluation models.

Every evaluation model will have some problems integrating other ones. Most of them have a particular purpose: algebra, theorem proving, predicate logics, planning, ...