[Haskell-cafe] Clearing up the status of GHCi on Raspberry Pi

[Dan Krol]

Hello,

There seems to be a bit of confusing information out there regarding what
is possible with regard to Haskell and Raspberry Pi. Specifically,
availability of GHCi (and as such, the ability to compile certain thing
such as Vector) in various versions of ghc.

Debian Weezy came with GHC 7.4.1. It doesn't come with GHCi. This fact was
reflected in what I've read online. So far so good.

Now, we come to GHC 7.4.2.:

http://www.haskell.org/haskellwiki/Raspberry_Pi#GHC_Status

This currently says the following:

"Note: GHCi does not currently work on ARM below version 7.4.2. See this
post on haskell-cafe for information on this

djhuk has been able to compile and install GHC-7.4.2 via QEMU to the
Raspberry Pi but there still seems to be some work to do."

This seems to imply that GHC 7.4.2. will include GHCi on arm. It implies
that, though there were at the time of writing some unspecified problems,
if one could get 7.4.2. working on their Rasperry Pi, one would get GHCi.
Futher, I extrapolated this to mean that any version later than 7.4.2.
would surely also have GHCi.

Under the "Found on mailing lists" of this link:

http://www.haskell.org/haskellwiki/ARM

I similarly found: "GHCi (7.4.2) is working on ARM (Cubieboard with
Ubuntu)" granted it doesn't say anything about Raspberry Pi.

Well, my experience has shown otherwise. I upgraded my Raspberry Pi to
Debian Jesse (currently the testing release), which gives me ghc as high as
7.6.3. GHCi? "command not found".

I asked about this in #haskell on freenode, and somebody pointed me here:

https://ghc.haskell.org/trac/ghc/wiki/Platforms

This seems to imply that ARM does not have GHCi (though version is not
specified in these tables). In fact, according to this same person, GHC
altogether will not officially be supported on ARM until version 7.8. I'm
not sure how that is reflected here. It seems to be Tier 2. Some Tier 2
things have GHCi.

I figure we should sort this out, I'd be happy to edit the wikis myself but
I want to make sure I understand what's going on. I understand this
probably comes down to some nuances that are not expressed here. For user
friendliness of the language and ecosystem I think such things should be
made clear. As somebody coming to this wanting to accomplish something, I
want a clear answer on what is available to me. It's been a source of
frustration for me.

Could somebody clear all this up for me? And while I'm at it, I would be
grateful if somebody could explain to me how it is possible (if at all) to
have ghci on my Raspberry Pi, short of compiling it myself. I'm not against
compiling ghc, but I am against compiling it on my Raspberry Pi. Qemu I
will consider, though.

Thanks a lot,

Dan
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