Add literal string constants (#19)

In addition, for the sake of Haskell code generation, this PR adds static typing
  with Statix.

  Resolves #5.

Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Reviewed-on: #19
Co-Authored-By: Glen Whitney <glen@nobody@nowhere.net>
Co-Committed-By: Glen Whitney <glen@nobody@nowhere.net>

trans/javascript.str

@@ -13,13 +13,25 @@ rules
 
   js: Stream()     -> $[Stdio]
   js: Int(x)       -> 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])]
   js: Terminate(x) -> x
   js: Sequence(l)  -> <join(|";\n")>l
 
+  /* Characters we need to escape in Javascript string constants */
+  Jscape: ['\t' | cs ] -> ['\', 't'  | cs ]
+  /* I think I can just use ASCII constants for characters... */
+  Jscape: [ 0   | cs ] -> ['\', '0'  | cs ]
+  Jscape: [ 8   | cs ] -> ['\', 'b'  | cs ] // Backspace
+  Jscape: [ 11  | cs ] -> ['\', 'v'  | cs ] // Vertical tab
+  Jscape: [ 12  | cs ] -> ['\', 'f'  | cs ] // Form feed
+
 strategies
+  javaLitString = un-single-quote
+                ; string-as-chars(escape-chars(Escape <+ Jscape))
+                ; single-quote
 
   javascript = bottomup(try(js))