GHCi is very useful and used separately of pure compiled Haskell code because of its :commands.

For instance :info <thing> gives you many informations regarding the infix and prefix notation of the thing, as weel as its precedence.

:t <expression> gives you the type of the expression, which is very useful to see the types of the parameters (and return) of a function, especially since there is type inference

It also allows variable redefinition, which isn't possible in "normal haskell code" but is useful for clear examples.

there is also special options which can for example be used to show timing of very specific expressions

@Jono2906 Done.

@FrenchMasterSword No, I said I don't know how to use it non-interactively, so it's not very well suited for TIO in its current form.

I'm building the new API with interactivity in mind, so in a hopefully not too distant future, I could add a proper GHCi REPL.