runghc is undocumented

[Isaac Dupree]

make install installs runghc, which is not mentioned anywhere in the user's guide.

So I didn't know whether it was a bug that runghc doesn't work when ghc is compiled without interactive(ghci) support. Also I need to pass --make to runghc in a multi-module program to make runghc work. Also I don't know if there's any GHC flag like ghc --run the way there is ghc --interactive for ghci (should there be? or is the syntax different enough that it would be troublesome?). Also #1312 and #1281 are about runghc's behavior...

At least runghc and runghc --help produce runghc: syntax: runghc [-f GHCPATH] [GHC-ARGS] FILE ARG... which is clear enough about the syntax, but not exactly the meaning.

[sorear]

runghc is implemented by calling GHCi, loading your module, and invoking 'main'. I'm extremely suprised that there is any situation where --make is required! So you can just run ghc -e main Main.hs, (approximately - runghc has other magic that is only sometimes useful. Read the source for details, it's <100 lines). Runghc is *primarily* intended for use as a #! interpreter, and is installed with a runhaskell symlink.

[Isaac Dupree]

Odd, I can't seem to reproduce needing --make, but I'm sure adding --make to runghc has been necessary for it to work for me more than once... maybe has something to do with some combination of .hi/.o files some of which are up to date for some modules? (observed on powerpc, whose ghci is not entirely perfect anyway it seems)

[igloo]

We should document runghc for 6.8.

[igloo]

I've added some basic docs.