feat: Type-dependent Haskell code generation

Caveat: type is still not being assigned for the Sequence()
  constructor.

  Also fixes the parsing of literal strings (whitespace just after
  the opening quote was being ignored, and was ambiguous just
  before the opening quote).

README.md

@@ -11,7 +11,8 @@ language as possible to work in, given that I inevitably will be doing a
 bunch of coding. The language will be centrally organized around the
 concept of "streams" (somewhat in the spirit of
 [streem](https://github.com/matz/streem) and/or
-[Orc](http://orc.csres.utexas.edu/index.shtml)). In fact all higher-type
+[Orc](http://orc.csres.utexas.edu/index.shtml), or to a lesser extent,
+[Sisal-is](https://github.com/parsifal-47/sisal-is)). In fact all higher-type
 entities will be cast in terms of streams, or in slogan form, "++f++unctions
 and (binary) ++o++perators are ++str++eams" (hence the name "fostr").
 

syntax/fostr.sdf3

@@ -14,7 +14,7 @@ lexical sorts
 
 lexical syntax
 
-  STRING_LITERAL = ~[\']*
+  STRING_LITERAL = "'"~[\']*"'"
 
 context-free sorts
 
@@ -38,7 +38,7 @@ context-free syntax
   TermEx.Terminate = <<Ex>;>
 
   Ex.Int       = INT
-  Ex.LitString = <'<STRING_LITERAL>'>
+  Ex.LitString = STRING_LITERAL
   Ex.Stream    = <stream>
   Ex.Sum       = <<Ex> +  <Ex>> {left}
   Ex.Gets      = [[Ex] << [Ex]] {left}

tests/basic.spt

@@ -1,15 +1,15 @@
 module basic
 language fostr
 
-
 test hw1_type [[
-[[stream]] << [['Hello,	world!']]
+[[stream]] << [['Hello,	world! ']] << [[3+2]] << ' times.'
 ]]
 run get-type on #1 to STREAM()
 run get-type on #2 to STRING()
+run get-type on #3 to INT()
 run get-type to STREAM()
 /** writes
-Hello,	world!**/
+Hello,	world! 5 times.**/
 
 /** md
 Title: A whirlwind tour of fostr

trans/haskell.str

@@ -1,15 +1,25 @@
 module haskell
-imports libstrategolib signatures/- util
+imports libstrategolib signatures/- util analysis
 rules
-  /* Approach: Generate code from the bottom up.
-     At every node, we create a pair of the implementation and
-     necessary preamble of IO actions.
-     We concatenate preambles as we go up.
-     Finally, at the toplevel we emit the preamble before returning the
-     final value.
+  /* Approach:
+     A) We will define a local transformation taking a term with value strings
+        at each child to a value string for the node.
+     B) We will append IO actions needed to set up for the value progressively
+        to a Preactions rule (mapping () to the list of actions). There will
+        be a utility `add-preaction` to append a new clause to value of this
+        rule.
+     C) We will use bottomup-para to traverse the full AST with the
+        transformation from A so that we have access to the original expression
+        (and get get the Statix-associated type when we need to).
+        Hence the transformation in (A) must actually take a pair of
+        an (original) term and a term with value strings at each child,
+        and be certain to return a value string.
+
+     Finally, at the toplevel we emit the result of <Preactions>() before
+     returning the final value.
    */
 
-  hs: TopLevel((c,p)) -> $[import System.IO
+  hs: (_, TopLevel(val)) -> $[import System.IO
   data IOStream = StdIO
 
   gets :: Show b => a -> b -> IO a
@@ -17,25 +27,35 @@ rules
     putStr(show d)
     return s
 
+  getsStr :: a -> String -> IO a
+  getsStr s d = do
+    putStr(d)
+    return s
+
   main = do
-    [p]return [c]]
+    [<Preactions>()]return [val]]
 
-  hs: Stream()             -> ("StdIO", "")
-  hs: Int(x)               -> (x, "")
-  hs: LitString(x)
-        -> ($["[<string-as-chars(escape-chars(HaskellEscape))>x]"], "")
-  hs: Sum( (c, p), (d, q)) -> ($[([c] + [d])], <conc-strings>(p,q))
+  hs: (_, Stream())     -> "StdIO"
+  hs: (_, Int(x))       -> x
+  hs: (_, LitString(x)) -> <haskLitString>x
+  hs: (_, Sum(x, y))    -> $[([x] + [y])]
 
-  hs: Gets((c, p), (d, q)) -> <hsget>(c,d,<conc-strings>(p,q),<newname>"fosgt")
-  hsget: (s, x, p, v) -> (v, <concat-strings>[p, $[[v] <- [s] `gets` [x]],
-                                              "\n"])
+  hs: (Gets(_, xn), Gets(s, x)) -> v
+    with v := <newname>"_fostr_get"
+       ; <add-preactions>[$[[v] <- [<hs_gets>(s, xn, x)]]]
+  hs: (To(xn, _), To(x, s))     -> v
+    with v := <newname>"_fostr_to"
+       ; <add-preactions>[$[let [v] = [x]], <hs_gets>(s, xn, v)]
 
-  hs: To(  (c, p), (d, q)) -> <hsto>(c,d,<conc-strings>(p,q),<newname>"fosto")
-  hsto: (x, s, p, v) -> (v, <concat-strings>[p, $[let [v] = [x]], "\n",
-                                             $[[s] `gets` [v]], "\n"])
+  hs_gets: (s, xn, x ) -> $[[s] [<hs_getOp>xn] [x]]
+  hs_getOp = get-type; (?STRING() < !"`getsStr`" + !"`gets`")
 
-  hs: Terminate((c,p))     -> ($[[c];;], p)
-  hs: Sequence(l)          -> (<last; Fst>l, <map(Snd); concat-strings>l)
+  hs: (_, Terminate(x)) -> $[[x];;]
+  hs: (_, Sequence(l))  -> <last>l
+  /* One drawback of using paramorphism is at the very leaves we have
+     to undouble the tuple:
+   */
+  hs: (x, x) -> x where <is-string>x
 
   /* Characters we need to escape in Haskell string constants */
   Hascape: ['\t' | cs ] -> ['\', 't'  | cs ]
@@ -47,9 +67,15 @@ rules
   Hascape: [ 12  | cs ] -> ['\', 'f'  | cs ] // Form feed
 
 strategies
-  HaskellEscape = Escape <+ Hascape
+  haskLitString = un-single-quote
+                ; string-as-chars(escape-chars(Escape <+ Hascape))
+                ; double-quote
 
-  haskell = bottomup(try(hs))
+  haskell = rules(Preactions: () -> ""); bottomup-para(try(hs))
+
+  /* See "Approach" at top of file */
+  add-preactions = newp := <conc-strings>(<Preactions>(), <lines>)
+                 ; rules(Preactions: () -> newp)
 
   // Interface haskell code generation with editor services and file system
   to-haskell: (selected, _, _, path, project-path) -> (filename, result)

trans/javascript.str

@@ -13,7 +13,7 @@ rules
 
   js: Stream()     -> $[Stdio]
   js: Int(x)       -> x
-  js: LitString(x) -> $['[<string-as-chars(escape-chars(JavaEscape))>x]']
+  js: LitString(x) -> <javaLitString>x
   js: Sum(x,y)     -> $[[x] + [y]]
   js: Gets(x, y)   -> $[[x].gets([y])]
   js: To(x, y)     -> $[to([x],[y])]
@@ -29,7 +29,9 @@ rules
   Jscape: [ 12  | cs ] -> ['\', 'f'  | cs ] // Form feed
 
 strategies
-  JavaEscape = Escape <+ Jscape
+  javaLitString = un-single-quote
+                ; string-as-chars(escape-chars(Escape <+ Jscape))
+                ; single-quote
 
   javascript = bottomup(try(js))
 

trans/python.str

@@ -15,7 +15,7 @@ rules
 
   py: Stream()     -> $[Stdio]
   py: Int(x)       -> x
-  py: LitString(x) -> $[r'[x]']
+  py: LitString(x) -> $[r[x]]
   py: Sum(x,y)     -> $[[x] + [y]]
   py: Gets(x, y)   -> $[[x].gets([y])]
   py: To(x, y)     -> $[to([x],[y])]