forked from glen/fostr
Glen Whitney
7feddbcfbe
Add the ! postfix operator and !! expression. Also add the ++ string concatenation operator. Also allow specification of standard input in the test scheme. Resolves #7, #18. Co-authored-by: Glen Whitney <glen@studioinfinity.org> Reviewed-on: glen/fostr#25 Co-Authored-By: Glen Whitney <glen@nobody@nowhere.net> Co-Committed-By: Glen Whitney <glen@nobody@nowhere.net>
102 lines
3.5 KiB
Plaintext
102 lines
3.5 KiB
Plaintext
module haskell
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imports libstrategolib signatures/- signature/TYPE util analysis
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rules
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/* Approach:
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A) We will define a local transformation taking a term with value strings
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at each child to a value string for the node.
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B) We will append IO actions needed to set up for the value progressively
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to a Preactions rule (mapping () to the list of actions). There will
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be a utility `add-preaction` to append a new clause to value of this
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rule.
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C) We will use bottomup-para to traverse the full AST with the
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transformation from A so that we have access to the original expression
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(and can get the Statix-associated type when we need to).
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Hence the transformation in (A) must actually take a pair of
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an (original) term and a term with value strings at each child,
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and be certain to return a value string.
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Finally, at the toplevel we emit the result of <Preactions>() before
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returning the final value.
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*/
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hs: (_, TopLevel(val)) -> $[-- Preamble from fostr
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import System.IO
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data IOStream = StdIO
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-- Danger: These currently assume the stream is 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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getsStr :: a -> String -> IO a
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getsStr s d = do
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putStr(d)
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return s
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emit s = do
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l <- getLine
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return (l ++ "\n")
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main = do
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[<Preactions>()]return [val]]
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hs: (_, Stream()) -> "StdIO"
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hs: (_, Int(x)) -> x
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hs: (_, LitString(x)) -> <haskLitString>x
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hs: (_, EscString(x)) -> x
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hs: (_, Sum(x, y)) -> $[([x] + [y])]
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hs: (_, Concat(x, y)) -> $[([x] ++ [y])]
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hs: (Gets(_, xn), Gets(s, x)) -> v
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with v := <newname>"_fostr_get"
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; <add-preactions>[$[[v] <- [<hs_gets>(s, xn, x)]]]
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hs: (To(xn, _), To(x, s)) -> v
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with v := <newname>"_fostr_to"
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; <add-preactions>[$[let [v] = [x]], <hs_gets>(s, xn, v)]
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hs_gets: (s, xn, x ) -> $[[s] [<hs_getOp>xn] [x]]
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hs_getOp = get-type; (?STRING() < !"`getsStr`" + !"`gets`")
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hs: (_, Emits(s)) -> v
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with v := <newname>"_fostr_emitted"
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; <add-preactions>[$[[v] <- emit [s]]]
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hs: (_, Terminate(x)) -> $[[x];;]
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hs: (_, Sequence(l)) -> <last>l
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/* One drawback of using paramorphism is we have to handle lists
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explicitly:
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*/
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hs: (_, []) -> []
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hs: (_, [x | xs]) -> [x | xs]
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/* Another drawback of using paramorphism is at the very leaves we have
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to undouble the tuple:
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*/
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hs: (x, x) -> x where <is-string>x
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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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haskLitString = un-single-quote
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; string-as-chars(escape-chars(Escape <+ Hascape))
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; double-quote
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haskell = rules(Preactions: () -> ""); bottomup-para(try(hs))
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/* See "Approach" at top of file */
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add-preactions = newp := <conc-strings>(<Preactions>(), <lines>)
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; rules(Preactions: () -> newp)
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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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