Include Merl in Syntax Tools

1 files changed, 102 insertions, 0 deletions

diff --git a/lib/syntax_tools/examples/merl/lispc.erl b/lib/syntax_tools/examples/merl/lispc.erl
new file mode 100644
index 0000000000..97072cdab7
--- /dev/null
+++ b/lib/syntax_tools/examples/merl/lispc.erl
@@ -0,0 +1,102 @@
+%% ---------------------------------------------------------------------
+%% Licensed under the Apache License, Version 2.0 (the "License"); you may
+%% not use this file except in compliance with the License. You may obtain
+%% a copy of the License at <http://www.apache.org/licenses/LICENSE-2.0>
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% @author Richard Carlsson <[email protected]>
+%% @copyright 2012 Richard Carlsson
+%% @doc Lisp compiler in Erlang.
+
+-module(lispc).
+
+-export([eval/1]).
+
+-record(st, {}).
+
+-include("lisp_test.erl").
+
+-include("merl.hrl").
+
+eval(Lisp) ->
+    compile(Lisp, tmp),
+    tmp:eval().
+
+compile(Lisp, ModName) ->
+    {Code, _} = gen(Lisp, #st{}),
+    Main = ?Q(["() ->",
+               "  __print = fun (S, Xs) -> io:format(S,Xs), [] end,",
+               "  __apply = fun erlang:apply/2,",
+               "  __plus = fun erlang:'+'/2,",
+               "  __equal = fun lisp:equal/2,",
+               "  __gt = fun lisp:gt/2,",
+               "  __knot = fun lisp:knot/1,",
+               "  __y = fun (F) ->",
+               "          (fun (X) -> F(fun (Y) -> (X(X))(Y) end) end)",
+               "           (fun (X) -> F(fun (Y) -> (X(X))(Y) end) end)",
+               "     end,",
+               "  _@Code"]),
+    Forms = merl_build:module_forms(
+              merl_build:add_function(true, eval, [Main],
+                                      merl_build:init_module(ModName))),
+    %% %% Write source to file for debugging
+    %% file:write_file(lists:concat([ModName, "_gen.erl"]),
+    %%                 erl_prettypr:format(erl_syntax:form_list(Forms),
+    %%                                     [{paper,160},{ribbon,80}])),
+    merl:compile_and_load(Forms, [verbose]).
+
+var(Atom) ->
+    merl:var(list_to_atom("__" ++ atom_to_list(Atom))).
+
+gen([lambda, Ps, B], St) when is_list(Ps) ->
+    case lists:all(fun is_atom/1, Ps) andalso
+        (length(Ps) =:= length(lists:usort(Ps))) of
+        true ->
+            Vars = [var(P) || P <- Ps],
+            {Body, St1} = gen(B, St),
+            {?Q("fun (_@Vars) -> _@Body end"), St1};
+        false ->
+            throw(bad_lambda)
+    end;
+gen([lambda | _], _) ->
+    throw(bad_lambda);
+gen([def, A, V, B], St) when is_atom(A) ->
+    Var = var(A),
+    {Val, St1} = gen(V, St),
+    {Body, St2} = gen(B, St1),
+    {?Q("(fun (_@Var) -> _@Body end)(_@Val)"), St2};
+gen([def | _], _) ->
+    throw(bad_def);
+gen([quote, A], St) ->
+    {merl:term(A), St};
+gen([quote | _], _) ->
+    throw(bad_quote);
+gen([iff, X, A, B], St) ->
+    {Cond, St1} = gen(X, St),
+    {True, St2} = gen(A, St1),
+    {False, St3} = gen(B, St2),
+    {?Q(["case _@Cond of",
+         "  [] -> _@False;",
+         "  _ -> _@True",
+         "end"]),
+     St3};
+gen([do], _) ->
+    throw(bad_do);
+gen([do | As], St0) ->
+    {Body, St1} = lists:mapfoldl(fun gen/2, St0, As),
+    {?Q("begin _@Body end"), St1};
+gen([list | As], St0) ->
+    {Elem, St1} = lists:mapfoldl(fun gen/2, St0, As),
+    {?Q("[ _@Elem ]"), St1};
+gen([_|_]=L, St) ->
+    {[F | As], St1} = lists:mapfoldl(fun gen/2, St, L),
+    {?Q("((_@F)(_@As))"), St1};
+gen(A, St) when is_atom(A) ->
+    {var(A), St};
+gen(C, St) ->
+    {merl:term(C), St}.