ARM is now a fully supported target platform for GHC Haskell

http://www.haskell.org/pipermail/haskell-cafe/2012-June/101704.html

by dons • 14 years ago

115 27 14 years ago

james4k• 14 years ago

So...what would be needed to see native Haskell iOS apps? :)

eru• 14 years ago

Doesn't Apple still forbid programs written in anything apart from Objective C, JavaScript (and a third language, that I don't remember)?

krevis• 14 years ago

The guidelines say nothing about any particular programming languages.

franzus• 14 years ago

No.

cantankerous2• 14 years ago

Knowing the Haskell community, they could probably convert GHC Core into idiomatic Objective-C if they really wanted to, but it's not necessary. RubyMotion and other platforms are accepted because they stick to Apple's guidelines. The same would go for a GHC-iPhone platform.

iPhone Monad, anyone?

ryannielsen• 14 years ago

Nope, not anymore. http://daringfireball.net/2010/09/app_store_guidelines

shriphani• 14 years ago

You can always compile scheme / haskell etc to C and then use it as a library. (gambit-scheme users do this).

Dn_Ab3• 14 years ago

Saw this recently. https://github.com/ghc-ios/ghc/wiki

It looks like there is no prebuilt package of interfaces with iOS so still a ways to go. Still great work though.

T_S_• 14 years ago

Cross compilation is not yet supported. You want to build on osx/intel and target ios/arm. Not yet. ghc still needs to target the platform it was built on.

Cieplak• 14 years ago

I just got my Raspberry Pi in the mail last week and was disappointed about the Haskell support. Now I'm ecstatic!

djhworld• 14 years ago

Don't get too excited just yet, here are my experiences so far attempting to get GHC 7.4 on my R-Pi

http://www.reddit.com/r/haskell/comments/u7cwv/some_observat...

cheatercheater• 14 years ago

The x86 and x64 have interesting hacks in the asm they generate. For example, thread switching is done not by a conditional jump, but by self-modifying code (there's some nops in the main loop, and they get overwritten with a jmp when it's time to preempt). What cool architecture-specific hacks does the ARM version use?

exDM694• 14 years ago

I assume you refer to the co-operative thread switching done by the GHC runtime to achieve co-operative multitasking with Haskell's green threads? I thought this was done by trashing all the registers (pushing live regs to stack) in the compiler back end and then swapping the stack pointer in the runtime. Are you sure about the nop's in the main loop?

I, too, would like to know how this works on ARM and other non-x86 platforms. Do they even have this feature supported on ARM? (ie. compile with ghc --threaded and then add RTS parameters as needed when executing)

_quasimodo• 14 years ago

What you describe is the actual procedure of switching threads. What cheatercheater describes is the mechanics of initiating this switch. You have "checkpoints" in the thread, where the thread finds out if it is to be descheduled and performs a conditional branch to the code that does what you described. Apparently in GHC code, there is no conditional branch instruction, an unconditional jump is generated on the fly, probably to avoid branch mispredictions.

dons2• 14 years ago

GHC uses pre-emptive thread switching, not co-operative thread switching. Threads are forced by the runtime to be switched out -- they have no choice in the matter -- based on rts interrupts.

Typically, threads will be switched when they allocate.

See

https://github.com/ghc/ghc/blob/master/rts/Schedule.c#L208

and for low-level fun:

https://github.com/ghc/ghc/blob/master/includes/stg/SMP.h

ARM is now a fully supported target platform for GHC Haskell

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