Make macros persist in REPL

This introduces a stateful version of the compiler, which holds on to
the compilation environment and can be given further code to compile
with respect to that environment.  This is great for the REPL, because
it means macros will be stored in the environment and persist for the
session.

It even works with transform macros given on the command line.

Closes anko#17.

src/cli.ls

@@ -77,6 +77,11 @@ else
 
   # Interactive stdin: start repl
   else
+
+    # Create a stateful instance of the compiler that holds on to a root macro
+    # environment.  This lets typed-in macros persist for the session.
+    stateful-compiler = esl.stateful compiler-opts
+
     # see https://nodejs.org/api/repl.html
     repl = require \repl
     vm = require \vm
@@ -86,6 +91,6 @@ else
         # NOTE: will fail on older nodejs due to paren wrapping logic; see
         # SO http://stackoverflow.com/questions/19182057/node-js-repl-funny-behavior-with-custom-eval-function
         # GH https://github.com/nodejs/node-v0.x-archive/commit/9ef9a9dee54a464a46739b14e8a348bec673c5a5
-        esl cmd, compiler-opts
+        stateful-compiler cmd
         |> vm.run-in-this-context
         |> callback null, _

src/env.ls

@@ -3,7 +3,7 @@
 # compilation.  Environment objects most importantly store the macro table of a
 # compilation scope.
 
-{ concat-map, unfoldr, map, reverse, fold } = require \prelude-ls
+{ keys, concat-map, unfoldr, map, reverse, fold } = require \prelude-ls
 es-generate = require \escodegen .generate _
 
 # Recursively search a macro table and its parents for a macro with a given

src/index.ls

@@ -2,7 +2,10 @@ string-to-ast = require \./parse
 ast-to-estree = require \./translate
 estree-to-js  = (require \escodegen).generate _
 
-module.exports = (input, options={}) ->
+root-macro-table = require \./built-in-macros
+environment = require \./env
+
+compile = (root-env, input, options={}) ->
 
   input .= to-string!
 
@@ -11,5 +14,17 @@ module.exports = (input, options={}) ->
 
   "(#input\n)" # Implicit list of everything (trailing \n terminates comments)
   |> string-to-ast
-  |> ast-to-estree _, transform-macros : options.transform-macros
+  |> ast-to-estree root-env, _, transform-macros : options.transform-macros
   |> estree-to-js
+
+
+make-stateful-compiler = (options={}) ->
+  root-env = environment root-macro-table
+  return compile root-env, _, options
+
+compile-once = (input, options={}) ->
+  root-env = environment root-macro-table
+  return compile root-env, input, options
+
+module.exports = compile-once
+  ..stateful = make-stateful-compiler

src/translate.ls

@@ -1,25 +1,21 @@
+# Turns an internal AST form into an estree object with reference to the given
+# root environment.  Throws error unless the resulting estree AST is valid.
+
 { concat-map }   = require \prelude-ls
 root-macro-table = require \./built-in-macros
 statementify     = require \./es-statementify
 environment      = require \./env
-{ list }         = require \./ast
 
 { create-transform-macro } = require \./import-macro
 
 { errors } = require \esvalid
 
-module.exports = (ast, options) ->
+module.exports = (root-env, ast, options={}) ->
 
   transform-macros = (options.transform-macros || []) .map (func) ->
     isolated-env = environment root-macro-table
     create-transform-macro isolated-env, func
 
-  # Create an extra node on the "linked list" of macro tables so multiple runs
-  # of the compiler have somewhere to put any new macro definitions, without
-  # changing the underlying root macro table.  This guards multiple compiler
-  # invocations from accidentally influencing each other.
-  root-env = environment root-macro-table
-
   statements = ast.content
 
   transform-macros .for-each (macro) ->