Question

I’ve sort of got Fsi.exe working as expected on a Mac OS X (Snow Leopard) with Mono. I just noticed a little bit of odd behavior with cut and paste and I was wondering if anyone had seen this.

I’ve defined the following alias for fsi:

alias fsi='ledit mono ~/FSharp-1.9.7.8_2/bin/fsi.exe --gui-'

ledit is an Ocaml utility that seems to make the keyboard input work correctly–without it, fsi just never seems to read the input. To see what I mean, try Fsi.exe without ledit and enter

let square x = x * x;;

without ledit, it just never seems to parse the input. I mean it never comes back to the “>” prompt after you enter the string. With ledit, the “>” prompt comes back immediately.

Of course the –gui- keeps fsi from displaying all the messages about the lack of System.Drawing etc.

So this all seems to work. The oddity is when I copy and paste code into the FSI, certain characters seem to repeat over and over again. It seems to be conditioned by the size of the buffer I’m pasting in. When I paste small snippets there seems to be no problem. But if I paste in larger chunks, there’s this oddity.

If I do the following:

open System.IO;;

then paste this code snippet in FSI:

let buildFileList basepath filespec =
    seq {
        yield! Directory.GetFiles(basepath, filespec, System.IO.SearchOption.AllDirectories)
        }

That works fine. But if I copy and paste in a bigger chunk of code ending with that, it repeats the portion up to the yield! over and over again. It seems to be somehow related to fsi attempting to parse the code as it’s being pasted in because the same code pasted in will cause parsing errors (like FS0010) when it’s pasted at the end of a long chunk but won’t cause an error when it’s isolated.

If I #load the entire file, it parses correctly as well so I think my code is ok.

This oddity in copy/paste seems to happen both with and without ledit on the command line. I don’t mind researching this issue myself but I’m kind of stumped about where I should proceed with this. I’m copying from GVim if that makes a difference but anyone have any idea where I might proceed in trying to isolate the cause of this odd behavior? I suppose I could take the extra step of copying into TextEdit first and then trying to copy into fsi but any ideas beyond that?

To bottom line this: has anyone else seen this odd behavior? If not, any suggestions about how I might proceed in trying to isolate the cause of this odd behavior?

Answer 1

When I encountered this behavior on my Mac, I went a different route. Instead of using ledit, I employed fsi‘s --readline option, seen below (where ${FSHARP} is my install path).

mono ${FSHARP}/fsi.exe --readline+ --gui-

You may also want to check your terminal settings. My terminal (for example) is declared as xterm-color, and I have unchecked delete sends CTRL-H. I think those are the only relevant settings, but don’t hold me to it.