Something along the lines of:
import GHC.Version qualified
main :: IO ()
main = print $ GHC.Version.current
-- would print Version 8 10 7
A roundabout way is to execute ghc --version from shell:
import System.Process
main = system "ghc --version"
but this may be incorrect when the running GHC isn't the same as the ghc in PATH.
Yes, in two ways. The first using System.Info.compilerVersion
import System.Info
main :: IO ()
main = print compilerVersion
-- prints "Version {versionBranch = [8,6], versionTags = []}"
Second via the CPP language extension:
{-# LANGUAGE CPP #-}
main :: IO ()
main = print __GLASGOW_HASKELL__
-- prints "806" (of type Integer)
Docs on how that number has been come up with.