When I use GHCi commands (i.e. any command starting with ":" for example :set t) on https://tryhaskell.org/ I get an error:

:1:1: parse error on input ‘:’

According to the documentation of GHCi this should work, but I cannot find much information about it.

I've tried a few other online "repls" as well.

CodePudding user response：

That repl probably doesn't try to provide all of GHCI's functionality. It probably wants to be stateless, so it just evaluates expressions one at a time. No variable definitions, no interacting with GHCI any other way, e.g. through :t. If you install GHCI yourself, you will have a functioning repl. Or, if you want an online repl, https://replit.com/languages/haskell seems to work fine for me.