Scopes and symbols

src/slimit/scope.py

@@ -0,0 +1,81 @@
+###############################################################################
+#
+# Copyright (c) 2011 Ruslan Spivak
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+#
+###############################################################################
+
+__author__ = 'Ruslan Spivak <ruslan.spivak@gmail.com>'
+
+
+class SymbolTable(object):
+    def __init__(self):
+        self.globals = GlobalScope()
+
+
+class Scope(object):
+
+    def __init__(self, enclosing_scope=None):
+        self.symbols = {}
+        self.enclosing_scope = enclosing_scope
+        self.name = ''
+
+    def define(self, sym):
+        self.symbols[sym.name] = sym
+        # track scope for every symbol
+        sym.scope = self
+
+    def resolve(self, name):
+        sym = self.symbols.get(name)
+        if sym is not None:
+            return sym
+        elif self.enclosing_scope is not None:
+            return enclosing_scope.resolve()
+
+    def get_enclosing_scope(self):
+        return self.enclosing_scope
+
+
+class GlobalScope(Scope):
+    pass
+
+
+class LocalScope(Scope):
+    pass
+
+
+class Symbol(object):
+    def __init__(self, name):
+        self.name = name
+        self.scope = None
+
+
+class VarSymbol(Symbol):
+    pass
+
+
+class FuncSymbol(Symbol, Scope):
+    """Function symbol is both a symbol and a scope for arguments."""
+
+    def __init__(self, enclosing_scope):
+        Symbol.__init__(self)
+        Scope.__init__(self, enclosing_scope)
+
+