Extraction from streams (#25)

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: #25
Co-Authored-By: Glen Whitney <glen@nobody@nowhere.net>
Co-Committed-By: Glen Whitney <glen@nobody@nowhere.net>

trans/desugar.str

@@ -17,6 +17,7 @@ rules
   
   defStream:  DefGets(x)  -> Gets(Stream(), x)
   defStream:  DefTo(x)    -> To(x, Stream())
+  defStream:  DefEmits()  -> Emits(Stream())
 
 strategies
 

trans/haskell.str

@@ -23,6 +23,7 @@ rules
   import System.IO
   data IOStream = StdIO
 
+  -- Danger: These currently assume the stream is StdIO
   gets :: Show b => a -> b -> IO a
   gets s d = do
     putStr(show d)
@@ -33,6 +34,10 @@ rules
     putStr(d)
     return s
 
+  emit s = do
+    l <- getLine
+    return (l ++ "\n")
+
   main = do
     [<Preactions>()]return [val]]
 
@@ -41,6 +46,7 @@ rules
   hs: (_, LitString(x)) -> <haskLitString>x
   hs: (_, EscString(x)) -> x
   hs: (_, Sum(x, y))    -> $[([x] + [y])]
+  hs: (_, Concat(x, y)) -> $[([x] ++ [y])]
 
   hs: (Gets(_, xn), Gets(s, x)) -> v
     with v := <newname>"_fostr_get"
@@ -52,6 +58,10 @@ rules
   hs_gets: (s, xn, x ) -> $[[s] [<hs_getOp>xn] [x]]
   hs_getOp = get-type; (?STRING() < !"`getsStr`" + !"`gets`")
 
+  hs: (_, Emits(s)) -> v
+    with v := <newname>"_fostr_emitted"
+       ; <add-preactions>[$[[v] <- emit [s]]]
+
   hs: (_, Terminate(x)) -> $[[x];;]
   hs: (_, Sequence(l))  -> <last>l
   /* One drawback of using paramorphism is we have to handle lists

trans/javascript.str

@@ -3,24 +3,41 @@ imports libstrategolib signatures/- util
 
 rules
   js: TopLevel(x) -> $[// Fostr preamble
+  const _fostr_readline = require('readline');
+  const _fostr_events = require('events');
+  const _fostr_rl = _fostr_readline.createInterface({input: process.stdin});
   const Stdio = {
-    gets: v => { process.stdout.write(String(v)); return Stdio; },
+    gets:  v => { process.stdout.write(String(v)); return Stdio; },
+    emit: async () => {
+            const [line] = await _fostr_events.once(_fostr_rl, 'line');
+            return line + "\n"; }
   }
   function to(data, strm) {
     strm.gets(data);
     return data;
   }
+
+  const _fostr_body = async () => {
   // End of preamble
 
-  [x]]
+    [x]
+
+  // Fostr coda
+    _fostr_rl.close()
+  }
+  _fostr_body();
+  ]
+    with line := "[line]"
 
   js: Stream()     -> $[Stdio]
   js: Int(x)       -> x
   js: LitString(x) -> <javaLitString>x
   js: EscString(x) -> x
-  js: Sum(x,y)     -> $[[x] + [y]]
+  js: Sum(x, y)    -> $[[x] + [y]]
+  js: Concat(x, y) -> $[[x] + [y]]
   js: Gets(x, y)   -> $[[x].gets([y])]
   js: To(x, y)     -> $[to([x],[y])]
+  js: Emits(x)     -> $[(await [x].emit())]
   js: Terminate(x) -> x
   js: Sequence(l)  -> <join(|";\n")>l
 

trans/ocaml.str

@@ -12,9 +12,10 @@ imports libstrategolib signatures/- util signature/TYPE analysis
 
 rules
   ml: (_, TopLevel(x)) -> $[(* fostr preamble *)
-  type stream = { getS: string -> stream }
+  type stream = { getS: string -> stream; emitS: unit -> string }
   let rec stdio = {
-    getS = (fun s -> print_string s; stdio)
+    getS = (fun s -> print_string s; stdio);
+    emitS = (fun () -> (read_line ()) ^ "\n");
   };;
   (* End of preamble *)
 
@@ -24,11 +25,15 @@ rules
   ml: (_, Int(x))       -> x
   ml: (_, LitString(x)) -> $[{|[<un-single-quote>x]|}]
   ml: (_, EscString(x)) -> x
-  ml: (_, Sum(x,y))     -> $[[x] + [y]]
+  ml: (_, Sum(x, y))    -> $[[x] + [y]]
+  ml: (_, Concat(x, y)) -> $[[x] ^ [y]]
+
   ml: (Gets(_,yn), Gets(x, y))
     -> $[([x]).getS ([<ml_str>(yn,y)])]
   ml: (To(xn,_),   To(x, y))
     -> $[let _fto = ([x]) in (ignore (([y]).getS ([<ml_str>(xn,"_fto")])); _fto)]
+  ml: (_, Emits(s))     -> $[[s].emitS ()]
+
   ml: (_, Terminate(x)) -> x
   ml: (_, Sequence(l))  -> <ml_seq>l
   

trans/python.str

@@ -8,6 +8,8 @@ rules
     def gets(self, v):
       print(v, file=sys.stdout, end='')
       return self
+    def emit(self):
+      return input() + "\n" # Python inconsistently strips when using input
   def to(data,strm):
     strm.gets(data)
     return data
@@ -21,8 +23,10 @@ rules
   py: LitString(x) -> $[r[x]]
   py: EscString(x) -> x
   py: Sum(x,y)     -> $[[x] + [y]]
+  py: Concat(x,y)  -> $[[x] + [y]]
   py: Gets(x, y)   -> $[[x].gets([y])]
   py: To(x, y)     -> $[to([x],[y])]
+  py: Emits(x)     -> $[[x].emit()]
   py: Terminate(x) -> $[[x];]
   py: Sequence(l)  -> <join(|"\n")>l
 

trans/statics.stx

@@ -222,6 +222,13 @@ This pattern lets us specify error messages.
     type_Ex(e2) == STREAM() | error $[Items may only be sent to Streams.]@e2.
   /* **/
 
+  ty_Ex(Concat(e1, e2)) = STRING() :-
+    type_Ex(e1) == STRING() | error $[Expression [e1] not String in concat.]@e1,
+    type_Ex(e2) == STRING() | error $[Expression [e2] not String in concat.]@e2.
+
+  ty_Ex(Emits(e)) = STRING() :- // At the moment, only stream is stdio
+    type_Ex(e) == STREAM() | error $[Only Streams may emit items.]@e.
+
   /** md
 ```