Hi Tim, When you say "multi-stage programming language" do you have a specific calculus in mind? I think this can mean lots of different things to different people. This is a topic I have been interested in recently. Cheers, Matt On Fri, Nov 17, 2017 at 6:05 PM, Tim Sheard wrote:

After many years of hoping someone else would do this, I would like to make GHC into a true multi-stage programming language. Here is how I thought I might approach this.

1) Use the GHC as a library module. 2) Use the LLVM backend.

I have no experience with either of these tools. Lets start simple, How would I write functions like

compile :: String -> IO PtrToLLVMCode -- where the string is a small Haskell program. llvmCompile :: PtrToLLVMCode -> IO PtrToMachineCode jumpTo:: PtrToMachineCode -> IO ans -- where ans is the "type" of the string.

Any thoughts on how to get started? What papers to read, examples to look at?

I'd love to move to some more disciplined input type, a sort of (mono) typed program representation (with similar complexity) to Template Haskell Exp type.

where (Exp t) is a data structure representing a Haskell program of type t.

All offers of advice accepted. I'm trying to get started soon, and good advice about what to avoid is especially welcome. If any one wanted to help with this, that would be great.

Tim Sheard

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Hi Tim, About using GHC as a library module, have you see the ongoing work on "native metaprogramming" in GHC at https://ghc.haskell.org/trac/ghc/wiki/NativeMetaprogramming and a child project at https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow There, online code generation is not of the highest priority, rather we are trying to open up the compiler from top to down: making available GHC's AST and then the parser and the typechecker have priority over the other functionalities down the pipeline (like the code generator).

If any one wanted to help with this, that would be great.

I am interested to hear more about the approach you have in mind, and would be happy to help. Yours, Shayan On Fri, Nov 17, 2017 at 6:05 PM, Tim Sheard wrote:

After many years of hoping someone else would do this, I would like to make GHC into a true multi-stage programming language. Here is how I thought I might approach this.

1) Use the GHC as a library module. 2) Use the LLVM backend.

I have no experience with either of these tools. Lets start simple, How would I write functions like

compile :: String -> IO PtrToLLVMCode -- where the string is a small Haskell program. llvmCompile :: PtrToLLVMCode -> IO PtrToMachineCode jumpTo:: PtrToMachineCode -> IO ans -- where ans is the "type" of the string.

Any thoughts on how to get started? What papers to read, examples to look at?

I'd love to move to some more disciplined input type, a sort of (mono) typed program representation (with similar complexity) to Template Haskell Exp type.

where (Exp t) is a data structure representing a Haskell program of type t.

All offers of advice accepted. I'm trying to get started soon, and good advice about what to avoid is especially welcome. If any one wanted to help with this, that would be great.

Tim Sheard

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Hi Tim, Several years ago I wrote a proof of concept of one way to implement this in Haskell, http://johnlato.blogspot.com/2012/10/runtime-meta-programming-in-haskell.htm... . I used TH to automatically lift expressions into a newtype-wrapped ExpQ that could be used for staged evaluation. More than one stage would probably have been tedious though, and a major problem with any non-trivial code was getting all the imports in place. I do think it would have been possible to automatically track imports though. Of course that was 5 years ago, so state of the art has moved on. TH has better facilities for this now, and the ghc API probably has something better too. On Fri, Nov 17, 2017, 10:06 Tim Sheard wrote:

After many years of hoping someone else would do this, I would like to make GHC into a true multi-stage programming language. Here is how I thought I might approach this.

1) Use the GHC as a library module. 2) Use the LLVM backend.

I have no experience with either of these tools. Lets start simple, How would I write functions like

compile :: String -> IO PtrToLLVMCode -- where the string is a small Haskell program. llvmCompile :: PtrToLLVMCode -> IO PtrToMachineCode jumpTo:: PtrToMachineCode -> IO ans -- where ans is the "type" of the string.

Any thoughts on how to get started? What papers to read, examples to look at?

I'd love to move to some more disciplined input type, a sort of (mono) typed program representation (with similar complexity) to Template Haskell Exp type.

where (Exp t) is a data structure representing a Haskell program of type t.

All offers of advice accepted. I'm trying to get started soon, and good advice about what to avoid is especially welcome. If any one wanted to help with this, that would be great.

Tim Sheard

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