Allow binary operators to be used as lambdas (#385)

* Add operator lambdas

* Do not register anonymous functions as called functions

* Add tests

* Update CHANGELOG

* Update the docs

* Do not allow (..) to be used as a lambda

* Rename the function sum to any

src/aeso_ast_infer_types.erl

@@ -1641,7 +1641,10 @@ infer_expr(Env, {app, Ann, Fun, Args0} = App) ->
             GeneralResultType = fresh_uvar(Ann),
             ResultType = fresh_uvar(Ann),
             when_warning(warn_unused_functions,
-                         fun() -> register_function_call(Namespace ++ qname(CurrentFun), Name) end),
+                         fun() -> if element(1, Name) == lam -> ok;
+                                     true -> register_function_call(Namespace ++ qname(CurrentFun), Name)
+                                  end
+                         end),
             unify(Env, FunType, {fun_t, [], NamedArgsVar, ArgTypes, GeneralResultType}, When),
             when_warning(warn_negative_spend, fun() -> warn_potential_negative_spend(Ann, NewFun1, NewArgs) end),
             add_constraint(

src/aeso_parser.erl

@@ -335,7 +335,7 @@ exprAtom() ->
     ?LAZY_P(begin
         Expr = ?LAZY_P(expr()),
         choice(
-        [ id_or_addr(), con(), token(qid), token(qcon)
+        [ id_or_addr(), con(), token(qid), token(qcon), binop_as_lam()
         , token(bytes), token(string), token(char)
         , token(int)
         , ?RULE(token(hex), set_ann(format, hex, setelement(1, _1, int)))
@@ -472,6 +472,19 @@ id()       -> token(id).
 tvar()     -> token(tvar).
 str()      -> token(string).
 
+binop_as_lam() ->
+    BinOps = ['&&', '||',
+              '+', '-', '*', '/', '^', 'mod',
+              '==', '!=', '<', '>', '<=', '=<', '>=',
+              '::', '++', '|>'],
+    OpToLam = fun(Op = {_, Ann}) ->
+                  IdL = {id, Ann, "l"},
+                  IdR = {id, Ann, "r"},
+                  Arg = fun(Id) -> {arg, Ann, Id, type_wildcard(Ann)} end,
+                  {lam, Ann, [Arg(IdL), Arg(IdR)], infix(IdL, Op, IdR)}
+              end,
+    ?RULE(parens(choice(lists:map(fun token/1, BinOps))), OpToLam(_1)).
+
 token(Tag) ->
     ?RULE(tok(Tag),
     case _1 of