commit 9e9fed8384649355805ca525330cce5138475501
Author: avitex <theavitex@gmail.com>
Date:   Wed Mar 13 23:10:46 2019 -0700

    Initial commit

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6f5ced1
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.vscode
+__pycache__
\ No newline at end of file
diff --git a/run.py b/run.py
new file mode 100644
index 0000000..3db87e9
--- /dev/null
+++ b/run.py
@@ -0,0 +1,56 @@
+from tango.vm import TangoVM
+
+if __name__ == '__main__':
+    code = """
+    (
+        (def hello "world")
+        (def foo "bar")
+        (def dance (
+            (def other "world")
+            (print (if (eq hello other) "the world is ok" "the world is broken"))
+        ))
+        (on "click" dance)
+        (dance)
+        (def hello "moon")
+    )
+    """
+
+    event_handlers = []
+
+    def builtin_on(vm, scope, event, handler):
+        handler = vm.eval_in_scope(scope, handler)
+        event_handlers.append((event, handler, scope))
+
+    def trigger_event(vm, trigger_event):
+        results = []
+        for event, handler, scope in event_handlers:
+            if trigger_event == event:
+                results.append(vm.eval_in_scope(scope, handler))
+        return results
+
+    def builtin_def(vm, scope, ident, val):
+        scope.set_def(ident, val)
+
+    def builtin_print(vm, scope, *args):
+        print(*vm.multi_eval_in_scope(scope, args))
+
+    def builtin_if(vm, scope, predictate, truthy, falsy = None):
+        if vm.eval_in_scope(scope, predictate):
+            return vm.eval_in_scope(scope, truthy)
+        elif falsy:
+            return vm.eval_in_scope(scope, falsy)
+        else:
+            return None
+
+    def builtin_eq(vm, scope, a, b):
+        a, b = vm.multi_eval_in_scope(scope, (a, b))
+        return a == b
+
+    vm = TangoVM()
+    vm.def_builtin('def', builtin_def)
+    vm.def_builtin('print', builtin_print)
+    vm.def_builtin('eq', builtin_eq)
+    vm.def_builtin('if', builtin_if)
+    vm.def_builtin('on', builtin_on)
+    vm.eval_string(code)
+    trigger_event(vm, 'click')
\ No newline at end of file
diff --git a/tango/__init__.py b/tango/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tango/parser.py b/tango/parser.py
new file mode 100644
index 0000000..1caf970
--- /dev/null
+++ b/tango/parser.py
@@ -0,0 +1,92 @@
+from tango.value import TangoIdent, TangoExpr
+
+PAREN_OPEN = '('
+PAREN_CLOSE = ')'
+DOUBLE_QUOTE = '"'
+WHITESPACE = ' \t\n\r'
+
+
+class StringReader:
+    def __init__(self, s):
+        self._src = s
+        self._len = len(s)
+        self._cur = -1
+
+    def next(self):
+        if self._len == self._cur + 1:
+            return None
+        else:
+            self._cur += 1
+            return self._src[self._cur]
+
+
+class TangoParser:
+    def __init__(self, src):
+        self._cur = None
+        self._src = src
+        self._next()
+
+    def parse(self):
+        while self._cur is not None:
+            self._skip_whitespace()
+            if self._cur is PAREN_OPEN:
+                return self._parse_expr()
+            elif self._cur is DOUBLE_QUOTE:
+                return self._parse_str()
+            elif self._cur.isalpha():
+                return self._parse_ident()
+            elif self._cur.isnumeric():
+                return self._parse_int()
+            else:
+                self._raise_invalid_char()
+
+    def _parse_expr(self):
+        expr = TangoExpr()
+        self._next()
+        while self._cur is not None:
+            self._skip_whitespace()
+            if self._cur is PAREN_CLOSE:
+                self._next()
+                return expr
+            else:
+                expr.append(self.parse())
+
+        self._raise_unexpected_end()
+
+    def _parse_ident(self):
+        ident = self._read_until(WHITESPACE + PAREN_CLOSE)
+        return TangoIdent(ident)
+
+    def _parse_str(self):
+        self._next()
+        s = self._read_until(DOUBLE_QUOTE)
+        self._next()
+        return s
+
+    def _parse_int(self):
+        s = self._read_until(WHITESPACE + PAREN_CLOSE)
+        return int(s)
+
+    def _read_until(self, delims):
+        s = ''
+
+        while self._cur is not None and self._cur not in delims:
+            s += self._cur
+            self._next()
+
+        return s
+
+    def _next(self):
+        self._cur = self._src.next()
+        return self._cur
+
+    def _raise_unexpected_end(self):
+        raise ValueError('Unexpected end of stream')
+
+    def _raise_invalid_char(self):
+        raise ValueError('Invalid chr: ' + self._cur)
+
+    def _skip_whitespace(self):
+        if self._cur in WHITESPACE:
+            while self._next() in WHITESPACE:
+                continue
\ No newline at end of file
diff --git a/tango/scope.py b/tango/scope.py
new file mode 100644
index 0000000..bbfbd2c
--- /dev/null
+++ b/tango/scope.py
@@ -0,0 +1,28 @@
+class TangoScope:
+    def __init__(self):
+        self.defs = {}
+
+    def set_def(self, ident, val):
+        self.defs[ident] = val
+
+    def get_def(self, ident):
+        return self.defs.get(ident)
+
+class ChildTangoScope(TangoScope):
+    def __init__(self, parent):
+        super().__init__()
+        self.parent = parent
+
+    def get_def_local(self, ident):
+        return self.defs.get(ident)
+
+    def get_def(self, ident):
+        local = self.get_def_local(ident)
+        if local is None:
+            return self.parent.get_def(ident)
+        else:
+            return local
+
+
+class RootTangoScope(TangoScope):
+    pass
\ No newline at end of file
diff --git a/tango/utils.py b/tango/utils.py
new file mode 100644
index 0000000..c169308
--- /dev/null
+++ b/tango/utils.py
@@ -0,0 +1,26 @@
+from tango.value import TangoIdent, TangoExpr
+
+def is_callable(fn):
+    return hasattr(fn, '__call__')
+
+
+def is_ident(ident):
+    return isinstance(ident, TangoIdent)
+
+
+def is_expr(expr):
+    return isinstance(expr, TangoExpr)
+
+
+def resolve_if_ident(scope, val):
+    if is_ident(val):
+        scope.get_def(val)
+    else:
+        val
+
+
+def resolve_idents(scope, vals):
+    resolved = []
+    for val in vals:
+        resolved.append(resolve_if_ident(scope, val))
+    return resolved
\ No newline at end of file
diff --git a/tango/value.py b/tango/value.py
new file mode 100644
index 0000000..d903bdd
--- /dev/null
+++ b/tango/value.py
@@ -0,0 +1,19 @@
+class TangoExpr(list):
+
+    @property
+    def is_unit(self):
+        return len(self) == 0
+
+    @property
+    def is_block(self):
+        return len(self) > 0 and isinstance(self[0], TangoExpr)
+
+    @property
+    def is_call(self):
+        return len(self) > 0 and isinstance(self[0], TangoIdent)
+
+
+class TangoIdent(str):
+
+    def __repr__(self):
+        return super().__str__()
diff --git a/tango/vm.py b/tango/vm.py
new file mode 100644
index 0000000..09b8e97
--- /dev/null
+++ b/tango/vm.py
@@ -0,0 +1,83 @@
+import tango.utils as utils
+from tango.value import TangoExpr, TangoIdent
+from tango.scope import RootTangoScope, ChildTangoScope
+from tango.parser import StringReader, TangoParser
+
+
+class TangoVM:
+    def __init__(self):
+        self.root_scope = RootTangoScope()
+
+    def eval_string(self, s):
+        r = StringReader(s)
+        p = TangoParser(r)
+        e = p.parse()
+        return self.eval(e)
+
+    def eval(self, expr):
+        if utils.is_expr(expr):
+            return self.eval_in_scope(self.root_scope, expr)
+        else:
+            raise ValueError('Root was not Tango Expression')
+
+    def def_builtin(self, ident, builtin):
+        if isinstance(ident, str):
+            ident = TangoIdent(ident)
+        if utils.is_ident(ident):
+            self.root_scope.set_def(ident, builtin)
+        else:
+            raise ValueError('Not ident')
+
+    def eval_in_scope(self, scope, val):
+        if utils.is_expr(val):
+            if val.is_unit:
+                return None
+            elif val.is_block:
+                return self._do_block(scope, val)
+            elif val.is_call:
+                return self._do_call(scope, val)
+        if utils.is_ident(val):
+            return scope.get_def(val)
+
+        return val
+
+    def multi_eval_in_scope(self, scope, vals):
+        return [self.eval_in_scope(scope, val) for val in vals]
+
+    def _do_eval_child(self, scope, expr, args = TangoExpr()):
+        child_scope = ChildTangoScope(scope)
+        child_scope.set_def('$', args)
+        return self.eval_in_scope(child_scope, expr)
+
+
+    def _do_block(self, scope, block_expr):
+        for expr in block_expr:
+            res = self.eval_in_scope(scope, expr)
+        return res
+
+    def _do_call(self, scope, call_expr):
+        fn_ident, *fn_args = call_expr
+        fn_args = TangoExpr(fn_args)
+        fn_body = scope.get_def(fn_ident)
+
+        if fn_body is None:
+            TangoVM._rt_error('ident `{}` is undefined'.format(fn_ident))
+
+        if utils.is_callable(fn_body):
+            return fn_body(self, scope, *fn_args)
+
+        if utils.is_expr(fn_body):
+            if fn_body.is_unit:
+                return None
+            if fn_body.is_block:
+                return self._do_eval_child(scope, fn_body, fn_args)
+            elif fn_body.is_call:
+                fn_body = self._do_call(scope, fn_body)
+                return self._do_eval_child(scope, fn_body, fn_args)
+
+        TangoVM._rt_error('fatal error')
+
+    @staticmethod
+    def _rt_error(msg):
+        raise RuntimeError(msg)
+