forked from glen/fostr
Glen Whitney
904f651897
Also rudimentary code generation. The difficulty is that for Haskell generation, we need to know whether an expression is a string or in to send it to standard output. So we will need to begin implementation of a type system for fostr.
58 lines
2.1 KiB
Plaintext
58 lines
2.1 KiB
Plaintext
module haskell
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imports libstrategolib signatures/- util
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rules
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/* Approach: Generate code from the bottom up.
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At every node, we create a pair of the implementation and
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necessary preamble of IO actions.
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We concatenate preambles as we go up.
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Finally, at the toplevel we emit the preamble before returning the
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final value.
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*/
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hs: TopLevel((c,p)) -> $[import System.IO
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data IOStream = StdIO
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gets :: Show b => a -> b -> IO a
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gets s d = do
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putStr(show d)
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return s
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main = do
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[p]return [c]]
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hs: Stream() -> ("StdIO", "")
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hs: Int(x) -> (x, "")
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hs: LitString(x)
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-> ($["[<string-as-chars(escape-chars(HaskellEscape))>x]"], "")
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hs: Sum( (c, p), (d, q)) -> ($[([c] + [d])], <conc-strings>(p,q))
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hs: Gets((c, p), (d, q)) -> <hsget>(c,d,<conc-strings>(p,q),<newname>"fosgt")
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hsget: (s, x, p, v) -> (v, <concat-strings>[p, $[[v] <- [s] `gets` [x]],
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"\n"])
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hs: To( (c, p), (d, q)) -> <hsto>(c,d,<conc-strings>(p,q),<newname>"fosto")
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hsto: (x, s, p, v) -> (v, <concat-strings>[p, $[let [v] = [x]], "\n",
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$[[s] `gets` [v]], "\n"])
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hs: Terminate((c,p)) -> ($[[c];;], p)
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hs: Sequence(l) -> (<last; Fst>l, <map(Snd); concat-strings>l)
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/* Characters we need to escape in Haskell string constants */
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Hascape: ['\t' | cs ] -> ['\', 't' | cs ]
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/* I think I can just use ASCII constants for characters... */
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Hascape: [ 0 | cs ] -> ['\', '0' | cs ]
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Hascape: [ 7 | cs ] -> ['\', 'a' | cs ] // Alert
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Hascape: [ 8 | cs ] -> ['\', 'b' | cs ] // Backspace
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Hascape: [ 11 | cs ] -> ['\', 'v' | cs ] // Vertical tab
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Hascape: [ 12 | cs ] -> ['\', 'f' | cs ] // Form feed
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strategies
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HaskellEscape = Escape <+ Hascape
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haskell = bottomup(try(hs))
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// Interface haskell code generation with editor services and file system
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to-haskell: (selected, _, _, path, project-path) -> (filename, result)
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with filename := <guarantee-extension(|"hs")> path
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; result := <haskell> selected
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