[Jtsummers]

Learning a new programming language isn't that hard of a task, every decent programmer will learn a dozen or maybe even dozens over their career.

Also, neither OCaml nor SML are hard to learn. Haskell is more challenging, but that's because it's become, in a sense, multiple languages. The core of Haskell is no harder than OCaml or SML to learn, except for reasoning about lazy evaluation and some of its consequences. All the things people use on top of Haskell, though, does make it more to learn but what you'd need to reach equivalent utility as SML or OCaml for a compilers course is not that hard to learn.

[remexre]

Many universities that use OCaml in upper-division courses also use it in lower-division; my university requires all CS majors to take a course that is taught in OCaml, and covers higher-order programming, "advanced" (Hindley-Milner) type systems, equational reasoning, etc., typically in their sophomore year.

The compilers class can then be taught in it without worrying about that problem much.