In Haskell, you put it in the pipeline: for instance,

    y = h (f (traceShowId (g x)))

(Haskell is normally pure, but these functions from Debug.Trace are a notable exception.)

You use a tee https://en.wikipedia.org/wiki/Tee_(command)

In Common Lisp you put the print statement inline, it will return the result of the form you pass it so it doesn't change the results. If you want to know what f is returning in the form (h (f (g x))) you'd (h (print (f (g x)))) and it will print what f returns to the repl.

Or use Stickers provided by Sly which sort of log things as they change. https://joaotavora.github.io/sly/#Stickers In that case you'd highlight the form starting at f, and turn a sticker on. Then run the code, sticker outputs into a window.