Ergonomic language features and lib cleanup

+ let bindings
+ where bindings
+ do notation

I explored enough of the alternative language design space and decided
that we should commit fully to Lambda style. That means no more highly
tacit/concatenative point-free/partial programs as default. We'll keep
taking advantage of those capabilities when it makes sense, but the
library will continue to see massive overhauls.

src/Research.hs

@@ -51,11 +51,13 @@ data LToken
   | LIntegerLiteral Int
   | LArrowLeft
   | LArrowRight
+  | LBindArrow
   | LNewline
+  | LIndent Int
   deriving (Eq, Show, Ord)
 
 -- Output formats
-data EvaluatedForm = Tree | FSL | AST | Ternary | Ascii | Decode
+data EvaluatedForm = Tree | FSL | AST | Ternary | Ascii | Decode | Number | StringLit
   deriving (Show)
 
 -- Environment containing previously evaluated TC terms
@@ -257,6 +259,8 @@ formatT AST          = show . toAST
 formatT Ternary      = toTernaryString
 formatT Ascii        = toAscii
 formatT Decode       = decodeResult
+formatT Number       = either (\e -> "<not-number: " ++ e ++ ">") show . toNumber
+formatT StringLit    = either (\e -> "<not-string: " ++ e ++ ">") show . toString
 
 toSimpleT :: String -> String
 toSimpleT s = T.unpack